Adhatoda Vasica&nbsp;attenuates inflammatory and hypoxic responses in preclinical&nbsp;&nbsp;mouse models: potential for repurposing in COVID-19-like conditions

doi:10.21203/rs.3.rs-105233/v2

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Adhatoda Vasica attenuates inflammatory and hypoxic responses in preclinical mouse models: potential for repurposing in COVID-19-like conditions

https://doi.org/10.21203/rs.3.rs-105233/v2

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published 06 Apr, 2021

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Background: COVID-19 pneumonia has been associated with severe acute hypoxia, sepsis-like states, thrombosis and chronic sequelae including persisting hypoxia and fibrosis. The molecular hypoxia response pathway has been associated with such pathologies and our recent observations on anti-hypoxic and anti-inflammatory effects of whole aqueous extract of Adhatoda Vasica (AV) prompted us to explore its effects on relevant preclinical mouse models.

Methods: In this study, we tested the effect of whole aqueous extract of AV , in murine models of bleomycin induced pulmonary fibrosis, Cecum Ligation and Puncture (CLP) induced sepsis, and siRNA induced hypoxia-thrombosis phenotype. The effect on lung of AV treated naïve mice was also studied at transcriptome level. We also determined if the extract may have any direct effect on SARS-CoV2 replication

Results: Oral administration AV extract attenuates increased airway inflammation, levels of transforming growth factor-b1 (TGF-b1), IL-6, HIF-1α and improves the overall survival rates of mice in the models of pulmonary fibrosis and sepsis and rescues the siRNA induced inflammation and associated blood coagulation phenotypes in mice. We observed downregulation of hypoxia, inflammation, TGF-b1, and angiogenesis genes and upregulation of adaptive immunity-related genes in the lung transcriptome . AV treatment also reduced the viral load in Vero cells infected with SARS-CoV2.

Conclusion: Our results provide a scientific rationale for this ayurvedic herbal medicine in ameliorating the hypoxia-hyperinflammation features and highlights the repurposing potential of AV in COVID-19-like conditions.

Pulmonology

Hypoxia

fibrosis

sepsis

angiogenesis

blood coagulation

SARS-CoV2

COVID-19

Adhatoda Vasica.

Increased alveolar hypoxic response levels are inevitable consequences of many respiratory disorders such as chronic obstructive pulmonary disease and pulmonary fibrosis [1,2]. The key player of cellular response to hypoxia is the hypoxia-inducible factor (HIF)-1α and its regulatory protein, the prolyl hydroxylase domain (PHD)-2 enzyme [3]. The induction of HIF-1α is considered to be pro-inflammatory. It leads to transcriptional activation of essential genes implicated in airway remodelling and inflammation, such as vascular endothelial growth factor, transforming growth factor-beta 1 (TGF-b1), inducible nitric oxide synthase, interleukin -17 (IL-17), and IL-6 [3,4]. Thus, it is not just a consequence of diseases, elevated tissue/cellular hypoxia actively participates in exaggerating the inflammatory response contributing to progressive lung damage/injury.

HIF-1α also plays a pivotal role in infection, especially in promoting viral and bacterial replication [5]. In the present COVID-19 pandemic caused by the severe acute respiratory coronavirus 2 (SARS-CoV2), the role of hypoxia response in inducing severe lung inflammation and other outcomes has been one of the most highlighted observations [6–10]. Clinically, the interaction of the host and SARS-CoV2 is broadly described in three stages: first, asymptomatic state; second, a non-severe symptomatic state characterized by upper airway and conducting airway response; third, severe respiratory symptomatic state with the presence of hypoxia, acute respiratory distress syndrome (ARDS) and progression to sepsis [7]. During incubation and non-severe state, a specific humoral and cell-mediated adaptive immune response is required to eradicate the virus and prevent disease progression to a severe condition. Thus, strategies to boost immune responses at this stage are undoubtedly important [7,11]. However, defective immune response causes further accumulation of immune cells in the lungs, progressing to aggressive production of a pro-inflammatory cytokine such as IL-6, TNF-α resulting in an influx of immune cells and cytokines that damage the airways/ lung architecture. This extended release of cytokines by the immune system in response to the viral infection and/or secondary infections causes severe inflammation, endothelial dysfunction, sepsis and multi-organ damage [7,11,12]. In addition, recent research also reports coagulation abnormalities in severe COVID-19 cases [13]. The relation of hypoxia-coagulation is well known, where we and others also showed the crucial role of cellular hypoxic response in the form of thrombosis and bleeding susceptibility through HIF-1α and vWF axis [14,15]. Thus, medicinal agents that possess immune-boosting and anti-hypoxic effects could hold a promise for a better therapeutic option to preclude the SARS-CoV2 infection and severity.

We have recently shown an extract of Adhatoda Vasica (AV); an ayurvedic medicine that possesses robust anti-hypoxic properties and can reduce severe airway inflammation induced by an augmented hypoxic response in treatment-resistant asthmatic mice [16]. The anti-HIF-1α effect of AV also restores the cellular hypoxia-mediated loss of mitochondrial morphofunction in vitro [16]. As a follow-up, we evaluated AV’s usefulness in other severe lung pathologies, where hypoxia signalling is pertinent, and which are relevant to the clinical course of COVID-19 namely lung injury, fibrosis, and thrombosis. Since viral proliferation may be altered by molecular modulation of such pathways, we further tested the potential of AV in limiting SARS-CoV2 proliferation .

Preparation of plant extract and LC-MS fingerprinting:

Adhatoda Vasica (AV) was collected from Delhi-NCR region, India in the flowering season (November to March). Water extract of plant (leaves, twigs and flowers) was prepared according to classical method described for rasakriya in Caraka Samhita [17]. The process for the formulation involved preparation of decoction condensation and drying as described in earlier study [18]. Chemical fingerprinting of prepared AV extract was carried out by LC-MS at SAIF, CSIR-CDRI, Lucknow, India.

Animals

The study was designed and performed following guidelines of the Committee for the Purpose of Control and Supervision of Experiments on Animals (CPCSEA) and approved by Institutional Animal Ethics Committee of CSIR-Institute of Genomics & Integrative Biology (IGIB), New Delhi, India. The BALB/c and C57BL/6 male mice (8-10 weeks old) were bred under the pathogen-free condition. They were acclimatized to animal house environment one week before starting the experiments at CSIR-IGIB, New Delhi, India and maintained according to guidelines of CPCSEA. All the surgical procedures were performed under sodium pentobarbital anaesthesia and maximum efforts are taken for minimum suffering of animals.

Grouping and treatment of mice

Mice were mainly divided into two groups as Vehicle and treatment according to the experiment. In case of Cecum ligation puncture (CLP) experiment (n = 5-9), BALB/c mice were divided in Vehicle ( distil water and 10% ethanol, oral) and CLP (mice underwent CLP surgery). CLP mice subdivide in CLP+Cyclo A (Cyclosporin A treated CLP mice) and CLP+AV-D2 (Adhatoda extract treated CLP mice) group. For CLP experiment, treatment of AV (130mg/kg dissolved in distilled water, oral) or Cyclo A ( Cyclosporin A, 15mg/kg dissolved in 10% ethanol, orall) was started two days (48hours) before CLP and was continued till the mice survives after CLP (figure 1). In that some mice (n=3-4) from each group were sacrificed after 20 hours of CLP to assess lung histology and cytokine levels. Similarly, in bleomycin fibrosis model (n = 5), C57BL/6 mice were divided in Vehicle (i.e. Sham), Bleo (bleomycin treated) and Bleo+AV-D2 (AV 130mg/kg treated Bleo mice). In that AV treatment was done from day 18 to 21, as shown in the schematic (figure 1A). Bleomycin (3.5 U/kg of mice) was given intratracheally to isoflurane-anesthetised C57BL/6 mice on day 0 of the protocol (figure 1) to induce fibrotic changes in mice as described previously [19]. For transcriptomic research (n = 4-5), BALB/c mice divided into Vehicle (distil water, oral) and Adhatoda Vasica (AV) extract group. AV group is further subdivided into two according to its dose: AV-D2 (Adhatoda Vasica extract 130 mg/kg, dissolved in distilled water, oral) and AV-D4 (Adhatoda Vasica extract 260 mg/kg, dissolved in distilled water, oral) as described previously [16]. Distil water or AV ( 130mg/kg or 260mg/kg) treatment was given to mice by oral gavage for consecutive four days as represented in the figure. In PHD2 siRNA induced hypoxia model (n = 4-5) BALB/c mice were divided in scrambled siRNA (Scrm siRNA), prolyl hydroxylase domain-2 siRNA (PHD2 siRNA) and AV-D4 treated PHD2 siRNA group (PHD2 siRNA+AV-D4) group. AV-D4 dose (260 mg/kg, dissolved in distilled water, oral) given for four consecutive days and 90µg siRNA (Sigma) administered intranasally which dissolved in ultrapure DNase and RNAse free water with in-vivo jetPEI as the transfection reagent (Polyplus Transfection, France) to isoflurane-anesthetised mice on day 1, 3 and 5th of the protocol.

Clotting and bleeding time assay, blood collection and platelet measurement

Tail bleeding was measured as described previously [15]. Briefly, anesthetized mice's tail amputated with a sharp scalpel, and bleeding time was then determined by monitoring the duration of animal tail bleeding until it ceased and was kept in a prone position and immersed in PBS. Clotting time measured by the capillary tube method. The mice's tail was cleaned with 70% alcohol and punctured with a 1ml syringe needle. Filled two capillary tubes with free-flowing blood from the puncture site after wiping the first drop of blood. Stop clock started and capillary tubes were broken to see whether a thin fibrin stand formed between two broken ends. After fibrin stand is observed, clotting time measured from the average of two capillary tubes. For platelet measurement, blood obtained by cardiac puncture and collected in EDTA coated MiniCollect tubes (Greiner Bio-One Gmbh, kremsmünster, Austria) as described [15]. The whole blood was used to measure total and of active Platelet count and was carried out through flow cytometry using FACSCalibur (BD Biosciences, USA). Briefly, diluted whole blood (1:4) in PBS was incubated with APC conjugated anti-CD62P (eBioscience Inc, San Diego, CA, USA) and FITC conjugated anti-CD41 (eBioscience Inc, San Diego, CA, USA) for 15 min. Matched fluorescein-conjugated isotype control antibodies were used simultaneously for staining for comparison. The activity was compared using CellQuest Pro software (BD Biosciences, USA).

Bronchoalveolar lavage fluid collection and histopathology

Bronchoalveolar lavage fluid (BAL) was collected by instilling 1 ml PBS into the tracheotomised airway and recovered BAL fluids were processed to get total leukocyte count, as described previously (). For lung histology, the lungs were excised and fixed in 10% buffered formalin. The fixed, paraffin-embedded tissues cut into 5um sections and either stained with hematoxylin and eosin (H&E) to asses inflammation or Masson’s trichome (MT) staining to assess collagen content.

Cecum ligation puncture (CLP) procedure

Mice were anesthetised by injecting intraperitoneally a solution of 1:1 ketamine (75mg/kg) and xylazine (15mg/kg). The abdomen was shaved, and the peritoneum area was disinfected betadine solution followed by wiping with a 70% alcohol. Under aseptic conditions, a 1 cm midline incision was made, and the cecum carefully exposed with the adjoining intestine. The cecum was then tightly ligated with a 3.0 Mersilk (PROLENE, 8680G; Ethicon) sutures at the base and punctured once with a 19-gauge needle on the same side of the cecum. A small amount of stool extruded to ensure patency of the puncture sites. The cecum then returned to the peritoneal cavity, and the wound was closed with 3.0 Mersilk sutures. Control mice (i.e. Sham), the cecum was exposed out and then returned to the peritoneum without ligation or puncture. Mice were resuscitated by injecting subcutaneously 1 ml of pre-warmed 0.9% saline solution using a 25G needle. After surgery, animals placed immediately to a cage with exposure to a heating lamp of 150W until they recovered from the anaesthesia. The recovery time is from 30 min to 1 hour. Mice were monitored every 12 hours for survival or euthanised after 20 hours (n=3) for measurement of cytokines while they were fed with their regular diet and water. Two independent experiments recorded the mortality of mice after CLP surgery.

TGF-b, IL-6,IFN-g, HIF-1α, PHD2, and vWF measurement

The levels of TGF-b, IL-6, IFN-g (BD, USA), HIF-1α (R&D, USA), PHD2 ((USCN, China) and vWF (USCN, China) were measured in lung tissue homogenate or in plasma of the mice by sandwich ELISA, as per manufacturer’s protocol.

RNA isolation and whole transcriptome analysis:

Total RNA was isolated from mouse lung tissue treated with AV (AVD2 and AV-D4) or distilled water (vehicle) using the RNeasy Plus Mini Kit (Qiagen, CA, USA) following the manufacturer's protocol. For genome-wide expression analysis, the Affymetrix GeneChip MTA 1.0 array was used according to the manufacturer's instruction. For each sample, 250 ng of RNA was quantified and hybridized to microarray chips following a series of consecutive steps described in the protocol. After hybridization, microarray chips are then scanned using an Affymetrix GCS 3,000 scanner (Affymetrix, CA, USA) and the signal values are further evaluated using the Affymetrix® GeneChip™ Command Console software. Raw data automatically extracted using the Affymetrix data extraction protocol in the Affymetrix GeneChip® Command Console® Software (AGCC). CEL file import, mRNA level, all analysis, and export of the results were all performed using Affymetrix® Expression Console™ software. A comparative study between the vehicle and the AV treated samples done by using fold-change and p-value, genes considered to the differentially expressed by applying the criteria of significance p-value less than or equal to 0.05.

Functional enrichment and Connectivity map analysis

For functional analysis, we used Enrichr (amp.pharm.mssm.edu) tool. For pathway and gene ontology analysis, we examined gene enrichment in Cellular Compartment, Biological Processes, BioPlanet, Wiki, KEGG human pathway and gene set enrichment was considered if P-value less than 0.05 in Enrich r tool. For connectivity map (CMap) analysis, differentially expressed genes ranked according to fold change and list of top 150 up and down-regulated genes compatible with the CMAP data signatures was used to query the connectivity using clue.io touchstone database. A positive score in CMap analysis indicates a similar expression pattern of AV with compared compounds’ gene expression signature, whereas a negative score indicates an opposite pattern.

Molecular docking

The complete genome sequence of the novel SARS-CoV-2 virus was obtained from the National Centre for Biotechnology Information (NCBI) nucleotide database (NC_045512.2). The available 3D crystal structures of all the target proteins such as 3CLpro, PLpro, RdRp, S-protein, ACE2 and JAK2 were taken from protein data bank [20]. Others structures (NSP4, NSP7, NSP8, NSP9, NSP13, NSP14, NSP15 and NSP16, and TMPRSS2) were built using homology modelling with suitable templates using Swiss model [21] and I-TASEER web-servers [22]. The active regions of the proteins were identified by COACH meta-server and the results were compared with results from CASTp web server [23]. The anti-COVID-19 activity of the compounds extracted from the Adhatoda vasica were investigated using Molecular Docking studies using Schrodinger suite (Maestro) [24] and AutoDock vina packages [25]. In Schrodinger suite, all the target proteins were prepared using protein preparation wizard that included optimization followed by minimization of heavy atoms of proteins. The energy minimized 3D structures of all the ligands were prepared using LigPrep. The best pose of ligands that fit well in the protein cavity was carried out using OPLS3 force field with Glide package in Extra Precision mode (XP) mode. According to the size of binding cavity of the proteins, the coordinates x, y and z of the grid box were chosen with the grid resolution of 1 Å for calculations using AutoDock vina package.

Cellular model, drug treatment and detection of SARS-CoV-2 using a qPCR assay

Vero cells were maintained in Dulbeco Minimum Essential Medium (Gibco) containing 10% Fetal Bovine Serum (Gibco) at 37°C, 5% CO₂. Cells were seeded into 96-well tissue culture plates 24 h prior to infection with SARS-CoV2 (Indian/a3i clade/2020 isolate) in BSL3 lab of CSIR-CCMB. The effect of (AV) aqueous extract was tested against the SARS-CoV2 virus [26] by taking different concentrations of AV: 100, 50, 12.5, 6.25 (µg/mL) in DMEM media. Briefly, the cells were primed with the AV for 2 hours. The virus inoculum (0.1 MOI) was added to the cells along with different concentrations of AV and were left for infection for 3 hours. Post-infection, viral inoculum was replaced with fresh media containing 10% FBS and were maintained at 37°C, 5% CO₂ until 72 hours. After 72 hours , cell supernatant was collected and spun for 10 min at 6,000 g to remove debris and the supernatant was transferred to fresh collection tubes. RNA was extracted from 200 μL aliquots of sample supernatant using the MagMAX^TM Viral/Pathogen Extraction Kit (Applied Biosystems, Thermofisher). Extraction of viral RNA was carried out according to the manufacturer’s instructions. The viral supernatants from the test groups were added into the deep well plate (KingFisher^TM Thermo Scientific) along with a lysis buffer containing the following components - MagMAX^TMViral/Pathogen Binding Solution; MVP-II Binding Beads; MagMAX^TMViral /Pathogen Proteinase-K of 260 μL; 10 μL; 5 μL respectively for 200μL of sample. RNA extraction was performed using KingFisher Flex (version 1.01, Thermo Scientific) by following manufactures instructions. The eluted RNA was immediately stored in -80⁰C until further use. The detection of SARS-CoV2 was done using COVID-19 RT-PCR Detection Kit (Fosun 2019-nCoV qPCR, Shanghai Fosun Long March Medical Science Co. Ltd.) according to the manufacturer’s instructions. The kit detects Envelope gene (E; ROX labelled), Nucleocapsid gene (N- JOE labelled) and open reading frame1ab (ORF1ab, FAM labelled) specific to SARS-CoV2 for detection and amplification of the cDNA. SARS-CoV-2 cDNA (Ct~28) was used as a positive control. The log viral particles and a semi–log graph was plotted through the linear regression equation obtained using the RNA extracted from the known viral particles by RT-qPCR, using N- and ORF1ab genes specific to SARS CoV2 virus and percent viral reduction was calculated, as described previously [27]. However, Ct value of N gene is considered to calculate the % viral reduction [27].

Statistical analysis

Statistical significance determined by one-way analysis of variance and analysis was done using GraphPad Prism software. In the case of mice experiment, all data represent mean ± SEM; n= 3-10 in each group and significance denoted by *p <0.05, **p <0.01, ***p <0.001. p-value > 0.05 is considered non-significant (NS). Significance of the survival study determined by Log-rank (Mantel-Cox) test using GraphPad Prism software.

AV treatments inhibits the bleomycin induced pulmonary fibrosis features as well as increased HIF-1α levels in mice

To test the effect of AV treatment on lung fibrosis, bleomycin treated mice were orally administered with AV (130mg/kg, AV-D2) as shown in figure 1A. We observed a significant increase in TGF-β1 and HIF-1α levels in bleomycin (Bleo) treated mice lung than control-Sham mice, which decreased after AV-D2 treatment (figure 1B, C). Masson's trichrome staining showed a marked increase in collagen deposition in Bleo mice lungs compared to Sham mice (figure 1D). AV-D2 treatment reduces this increased collagen deposition in Bleo mice (figure 1D).

AV ameliorates the hallmarks of lung inflammation and injury in mice model of sepsis

Mice that underwent CLP (Cecal ligation and puncture) surgery did not show significant increase in HIF-1α levels after 20 hours of surgery (figure 1F). Still, its downstream target, such IL-6, was significantly increased (figure 1G), and IFN-g was decreased (figure 1H) in lung homogenate after 20 hours of surgery compared to sham mice. AV pre-treatment restored the levels of both cytokines in mice lungs, whereas Cyclo-A (a positive control) pre-treatment reduced only IL-6 levels in mice (figure 1G, H). Besides, histological analyses showed that CLP mice lung sections stained with haematoxylin and eosin (H&E) had increased inflammation and blood exudation (figure 1I). Pre-treatment of AV-D2 and Cyclo A to CLP mice showed reduced inflammation and blood exudation in lung histological sections (figure 1I). CLP surgery also leads to a significant decrease in mice survival rate compared to sham group (figure 1J). Treatment of Cyclo-A or AV-D2 to CLP mice significantly increases their survival rate compared to CLP untreated mice (figure 1J). In CLP+Cyclo A and CLP+AV-D2 group, the mice survival rate after 24 hours is 66.6 and 44.4 %, respectively (figure 1K). Though, in both groups, survival rate is 33.33% at the end of 142 hours of CLP surgery (figure 1K).

AV treatment inhibits hemostatic outcomes of hypoxia response induced by PHD2 siRNA in mice

Next, to test whether anti- HIF-1α effects of AV also prevents the blood coagulation phenotype [15], we treated naïve BALB/c mice with AV-D2 (130 mg/kg) and AV-D4 (260 mg/kg) concentration (figure 2A). Oral administration of AV-D2 and AV-D4 to naïve mice does not cause any significant change in body weight and lung and liver histological architecture (figure 2B, C), indicating its non-toxic nature. In the hemostasis parameter, treatment of AV-D4 dose to naïve healthy BALB/c mice causes a decrease in total as well as activated platelet count. Still, it does not affect mice tail bleeding time (figure 2D, E). To confirm the above-observed effect of AV-D4 on blood parameters, we induce cellular hypoxia response in mice by specific PHD2 siRNA treatment (figure 2F), as described previously [15]. PHD2 siRNA treatment (figure S1A) leads to a significant decrease in blood clotting and tail bleeding time (figure 2G). It also causes an overall increase in total and activated platelet count in mice blood (figure 2H). These changes induced by PHD2 siRNA are associated with increased blood HIF-1α and vWF levels, indicating the development of platelet aggregation (figure 2I, J). Interestingly, AV-D4 treatment to PHD2 siRNA mice causes a significant reversal of blood coagulation phenotype in terms of mice's blood clotting time, platelet count (total and active), and vWF levels (figure 2 G-I). These effects of AV are associated with the reversal of increased blood HIF-1α levels (figure 2J). However, AV treatment does not affect the mice's bleeding time, which was reduced after PHD2 siRNA treatment (figure 2G).

Modulation of immune response and hypoxia pathway genes: Revealed from lung transcriptome of AV treated mice

Lung transcriptomic analysis showed an upregulation of 1258 genes after AV-D4 treatment and 375 gens after AV-D2 treatment in naive mice. While, 1133 genes in AV-D4 and 262 genes in AV-D2 were downregulated, compared to Vehicle (distilled water) treated mice. We observed enrichment of pathways like IL-2 signaling, T cell signaling, T cell-mediated immunity, natural killer cell-mediated cytotoxicity, Haematopoietic cell lineages in the AV-D4 up-regulated genes. Similarly, biological processes like neutrophil activation and degranulation, neutrophil-mediated immunity, immune response regulation, and cellular defense response was enriched in AV-D4 up-regulated genes (figure 3A). In AV-D2 up-regulated genes, pathways relevant in mitochondria, T cell signaling, cytotoxic T cell-mediated immune response are enriched (figure 3A). At the same time, pathways like collagen biosynthesis, extracellular matrix organization, TGF beta regulation, hypoxia, and associated inflammatory MAPK-signaling are significantly enriched in both AV-D4, and AV-D2 downregulated genes (figure 3A). Overall, it indicates that AV treatments favour the expression of genes important in immunity and adaptive immune response and inhibitory to genes involved in hypoxia associated angiogenesis, fibrosis, and inflammatory cascade. These findings of AV might be relevant in COVID-19 treatment, where inhibition of adaptive immune response and induction of hypoxia-inflammatory response seen in SARS-CoV2 infected patients samples [9,10,28–30]. Besides, increased levels of immune cells in bronchoalveolar lavage fluid (BAL) of mice treated with AV, compared to vehicle-treated mice (figure S1B) further support our observation. Furthermore, to identify similarities and differences in AV gene expression pattern with other FDA-approved drugs and bio-actives, we mapped the transcriptomic signature of AV using Connectivity Map (CMap) database. We observed drugs like glucocorticoids, HDAC inhibitors ,and NSAIDS agents (that target cyclooxygenase) have a similar gene expression patterns with AV (figure S1C). These drugs or compounds are shown to have therapeutic potential against COVID-19 [31–34]. The possibility of such directs effects was further examined.

In silico and in vitro analysis demonstrates the therapeutic potential of AV against SARS-CoV2

Chemical components present in Adhatoda Vasica (table S1, S2) were examined by molecular docking analysis with SARS-CoV2 and host proteins. Tables 1 and S1 represent the docking results of the constituents of Adhatoda vasica with key target proteins of the SARS-CoV-2 virus. The compounds such as Luteolin-6,8-di-C-glucoside (-9.91 kcal/mol for 3CLpro, -9.43 for S-protein, -15.25 for NSP14, -11.12 for TMPRSS2, -9.82 for ACE2), Luteolin-6-C-glucoside-8-C-arabinoside (-11.59 kcal/mol for 3CLpro, -14.99 for NSP14, -13.46 for JAK2) and Apigenin-6,8-di-C-arabinoside (-11 kcal/mol for 3CLpro , -12.17 kcal/mol for NSP14, -10.77 for JAK2), Kaempferol_3_O_rutinoside (-8.9 kcal/mol for 3CLpro , -12 kcal/mol for NSP14, -11.77 for JAK2) shows higher docking score values to the viral and host target proteins essential for SARS-CoV2 transcription, replication and infection (table 1 and S1). The key residues of target proteins that contribute more for binding with the compounds of Adhatoda vasica are shown in Table S2. The compound Luteolin-6-C-glucoside-8-C-arabinoside makes cation-π interaction with residue (His 41) of 3CLpro with higher affinity -11.59 kcal/mol (figure 3B). The π-π stacking interaction between the Luteolin-6,8-di-C-glucoside and residues (Phe 426 and Phe 506) of NSP14 protein enhances the binding affinity to -15.25 kcal/mol when compared to other compounds as shown in figure 3C, and other interaction plots are represented in Supporting material figure S2 and 3. In addition, AV's flavonoids are also shown to have a higher binding affinity for proteins involved in hypoxia and inflammation [16]. To confirm the in-silico observation, we tested the anti-SARS-CoV2 potential of AV using in vitro model of SARS-CoV2 infection. We observe a 63% viral reduction after AV treatment (100 µg/ml) in Vero cells infected with SARS-CoV2, compared to the untreated group (figure 4). These results further substantiate the potential of AV in treating COVID-19.

Adhatoda Vasica or Vasa has been extensively used in Ayurveda for treating a wide range of inflammatory and respiratory conditions [35]. Even in modern clinical practice, it is recommended for strong bronchodilatory and antitussive effects [35,36]. AV’s active ingredients and their derivates such as Bromhexine, and Ambroxol are effective against various respiratory ailments like asthma, COPD, and tuberculosis [35]. We have recently shown that AV alleviates the severe airway inflammation in steroid-nonresponsive asthmatic by inhibition of HIF-1α (key transcription factor in hypoxia) via its negative regulator, PHD2., AV thereby modulates hypoxic response, which forms the basis for its diverse therapeutic effects including amelioration of mitochondrial dysfunction [16]. In this study we examined anti-hypoxic effects of AV in other hypoxia-inflammation prevalent conditions such as lung injury, fibrosis, and thrombosis. These are relevant to the current global pandemic of COVID-19, specifically progression and sequelae of SARS CoV2 infection (figure 5).

Our study shows that AV could reverse the pulmonary fibrosis (PF) pathological features in the bleomycin mice model (figure 1). HIF-1α stabilization is observed in many cell types of PF lungs and causes increase in collagen synthesis, fibrosis, TGF-β1, VEGF levels, and proliferation of fibroblasts [1,37]. AV treatment reduces the increased expression of HIF-1α protein in bleomycin treated mice lungs and attenuates increased TGF-β1 and collagen content in mice lungs (figure 1A-D). These preliminary results substantiate the hypoxia modulating effect of AV in chronic lung disease conditions such as fibrosis. There were strong effects of AV treatment on inflammatory lung injury and CLP induced lung injury and mortality in mice was reduced (figure 1I-K). Interestingly, we observed a decrease in IFN-g levels upon CLP in mice, which was restored after AV treatment (figure 1H). Our observation with the IFN-g level in CLP mice is not in line with previous studies [38], and it is likely due to the differences in the time of measurement after CLP. We speculate that the mechanism of AV action may not be directly anti-inflammatory but rather restoration of appropriate inflammatory responses and blocking of inappropriate inflammation. This would be similar to the clinical findings that support the adjuvant IFN-g immunotherapy concept to improve the host immune response against infection [39,40]. AV treatment also reduced the HIF-1α induced pro-thrombotic state that may additionally be relevant to lung injury and inflammation (figure 2F-J).

In the course of our study, we realized that the effects of AV on phenotypic features of the lung and systemic inflammation could also prove beneficial for the present pandemic situations. In SARS-CoV2 infection, elevated hypoxia response seems to be a consequence of hyper-inflammation that contributes to disease severity [6,7]. We relate the therapeutic relevance of AV for the above-observed effects against severe patho-phenotypes associated with the critical stage of COVID-19, characterized by severe lung inflammation, hypoxemia, angiogenesis, sepsis, and altered coagulation profile [6,8,11–13]. Therefore, the anti-hypoxic property of AV would be advantageous in attenuating the critical inflammatory stage of COVID-19. Our transcriptome results of AV treated mice also show down-regulation of genes related hypoxia-inflammation pathway (figure 3A). In view of the multitude of effects of AV that may alter cellular response to infection (Figure 5), we further determined whether there may be a direct or indirect effect of AV on SARS-CoV2 proliferation. We screened AV's chemical components against SARS-CoV2 and host target proteins and found possible interactions with both (table 1, S1, and S2) [41]. The in vitro viral inhibition supports that these may be relevant (figure 4). More studies are warranted to confidently determine whether there is meaningful anti-viral activity against SARS-CoV2.

Treatment of Adhatoda Vasica extract alters the cellular hypoxic response and modulates the inflammation-thrombosis axis to reduce lung injury, thrombosis and fibrosis. Moreover, in-silico and in vitro analysis suggest its role in preventing viral entry and replication. AV is a suitable candidate for clinical trials in COVID-19 patients.

HIF-1α: hypoxia inducible factor-1 α; PHD2: prolyl hydroxylase domain 2; COVID-19: Coronavirus disease-2019; AV: Adhatoda Vasica; TGF-b1: transforming growth factor-b1; IL-6: Interleukin-6; IL-17: Interleukin-17; IFN-g: interferon gamma; CLP: Cecum Ligation and Puncture; PHD2: Prolyl hydroxylase domain 2; SARS-CoV2: Severe acute respiratory coronavirus 2; PBMC: Peripheral blood mononuclear cell; BALF: Bronchoalveolar lavage fluid; ARDS: Acute respiratory distress syndrome; vWF: von Willebrand factor; Bleo: Bleomycin treated mice; H&E: hematoxylin and eosin; MT: Masson’s trichome; CMap: connectivity map; nsp: non-structural protein; 3CLpro: 3C-like protease; PLpro: Papain-like protease; RdRP: RNA-dependent RNA polymerase; S-pro: Spike protein; ACE2: Angiotensin-converting enzyme 2; TMPRSS2: Transmembrane Serine Protease 2; JAK: Janus kinase.

Ethics approval statement

The mice experiment was designed and performed following guidelines of the Committee for the Purpose of Control and Supervision of Experiments on Animals (CPCSEA) and approved by Institutional Animal Ethics Committee of CSIR-Institute of Genomics & Integrative Biology (IGIB), New Delhi, India.

In vitro viral culture ethical approval- to add

Consent for publication

Not applicable

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. The transcriptome data from this study have been submitted to the Gene Expression Omnibus (GEO) under the accession number: GSE156759

Funding: This work is supported by grant to CSIR-TRISUTRA (MLP-901) from the CSIR and Center of Excellence grant by Ministry of AYUSH, Govt. of India.

Competing interests

The authors declare that they have no competing interests.

Authors’Contributions

A.G. designed and performed the experiment, analysed the results and wrote the paper. D. D. performed CMap analysis and interpreted the results. S. K. performed molecular docking analysis. L.P., B.R.P. and V.J. contributed to animal model experiments. Y.P., M.G.E. performed in vitro screening against SARS-COV2 culture, R.R. contributed to analysis and manuscript writing, K.K.B. designed, performed, interpreted the in vitro SARS-COV2 culture results and wrote the paper. V.S. designed, performed, interpreted the molecular docking analysis and wrote the paper. B.P. conceptualized the study, provided AV, quality control information, designed the experiment, analysed and discussed the results and wrote the paper. A.A. and M.M. designed experiments, analysed and discussed the results and wrote the paper. All the authors reviewed and approved the final version of the manuscript.

Acknowledgments

We acknowledge animal house and imaging department for access to facility. We thank Dr. Ramniwas Prasher for his valuable suggestions regarding AV extract preparation and its use in clinical terms of Ayurveda. We also thank Arjun Ray for discussion and suggestion in molecular docking analysis. AG, LP and KK acknowledge AcSIR (Academy of Scientific and Innovative Research) for PhD. registrations and CSIR (Council of Scientific and Industrial Research) for fellowship.

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Adhatoda Vasica attenuates inflammatory and hypoxic responses in preclinical mouse models: potential for repurposing in COVID-19-like conditions

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