Acute respiratory failure is the most important component of multi-organ dysfunction (MODS) after intestinal damage and is an important cause of morbidity and mortality in critically ill patients. Intestinal ischemia-reperfusion causes a widespread systemic inflammatory response, resulting in MODS with subsequent acute lung injury. Disturbance in the intestinal epithelial barrier following intestinal ischemia causes activation of proinflammatory cytokines and circulating leukocytes [2]. TNF alpha, reactive oxygen substrate(ROS), and IL-6 are present in tissue damage that occurs during ischemia-reperfusion, these toxic molecules cause changes in the structure of cellular proteins, lipids, and ribonucleic acids that cause cell dysfunction or death [5]. Tissue hypoperfusion secondary to ischemia results in an increase in adhesion molecules on the endothelial cell surface in addition to these changes. The interaction between activated leukocytes and endothelial cells causes the migration of leukocytes and the production of proteases and ROS. Failure to control this inflammatory response causes tissue damage [2]. In our study, there were significant elevations of AST, ALT, and creatinine due to damage to the liver and kidney tissue in rats treated with I/R. Reperfusion following intestinal ischemia is associated with acute lung injury characterized by increased microvascular permeability, histological evidence of alveolar-capillary endothelial cell damage, and lung deposition of neutrophils. Typical histological features in the I/R group were edema, hemorrhage, increased alveolar wall thickness, and inflammatory cell infiltration in the alveolar spaces of the lung tissue.
In clinical and experimental studies, it has been shown that there is a rapid release of proinflammatory cytokines in ischemia-reperfusion of solid organs such as the lung. TNF alpha, ROS, and IL-6 are present in tissue damage that occurs during ischemia-reperfusion, these toxic molecules cause changes in the structure of cellular proteins, lipids, and ribonucleic acids that cause cell dysfunction or death [15].
Free radicals formed during ischemia-reperfusion are very important. Apoptosis occurs through two pathways, the mitochondrial-dependent intrinsic pathway activated by ROS, and the extrinsic pathway linked to inflammatory molecules such as TNF alpha. The intrinsic pathway is activated in the early phase of reperfusion, the extrinsic pathway is activated a few hours after reperfusion. Both pathways accelerate the activation of caspases and proteases responsible for the clearance of specific cellular substrates that cause cell death [5]. Using an experimental lung ischemia-reperfusion model, Forgiarini et al. showed that there is a large number of apoptotic cells with increased caspase 3 activity after ischemia [16]. It has been shown that caspase 3, 8, and 9 activities are increased in lung tissue samples in programmed cell damage after ischemia-reperfusion injury in lung transplantation [17]. In our study, significantly increased IL-1, IL-6, TNF-alpha staining, and diffuse caspase 3,8 and 9 activity were observed in the lung tissue after I/R.
Many treatment options have been tried to prevent or minimize cell death that occurs during ischemia-reperfusionfusion. Sodium-glucose cotransporter 2 (SGLT2) inhibitors-, have been shown to have anti-inflammatory, antioxidant, and antifibrotic properties in cardiovascular diseases and renal damage. In lung infections, it has been shown to effectively reduce Pseudomonas infection and increase antibiotic effectiveness in diabetic rats. Therefore, the idea that SGLT2 inhibitors may show potential benefit in lung diseases has arisen. In the study of Lina et al. canagliflozin successfully reduced inflammatory cell infiltration, congestion, and edema in the lung [18]. Kıngır et al. reported that dapagliflozin provided mild histological improvement by reducing oxidative stress and inflammation (TNF-α) in lung tissue [19].
There are few studies in the literature on the pulmonary protective effect of empagliflozin. Ojima et al. (2015) also reported that empagliflozin exerts its anti-inflammatory and antifibrotic effects by inhibiting pro-inflammatory cytokine expression and by suppressing advanced glycosylation products and receptor axis [8]. In the study of Hess et al. it was shown that the number of pro-angiogenic CD133 + progenitor cells in the circulation increased, pro-inflammatory granulocyte precursors decreased, and the anti-inflammatory M2 polarization of monocytes increased with 6-month empagliflozin administration (20). Chowdhury et al. stated that empagliflozin treatment can reduce pulmonary artery remodeling by increasing apoptosis and decreasing the proliferation rate in the pulmonary artery vascular Wall. The effect of empagliflozin on pulmonary artery remodeling in Covid infection has been explained by a similar protective effect [21]. Histopathological and immunohistochemical improvements were observed in the lung tissue with empagliflozin treatment. Kabel et al. showed that empagliflozin can suppress the expression of TGF-β1, TNF-α, and IL-6 and caspase 3 expression in lung tissue in bleomycin-mediated lung injury. They observed histopathological and immunohistochemical improvements in the lung tissue with empagliflozin treatment. Elmaaboud et al. (2019) et al. also supported the view that empagliflozin inhibits apoptosis by suppressing caspase 3 expression [8, 22]. In our study, we observed that the lung damage developed after I/R in rats pre-treated with empagliflozin was significantly milder compared to the placebo group that was not given empagliflozin. In the immunohistochemical staining of the lungs of rats given empagliflozin, it was shown that the number of cells showing inflammatory cytokines such as IL-1, IL-6, and TNF-alpha and caspase 3,8 and 9 activity was lower. The relationship between lung injury due to ischemia-reperfusion injury and oxidative stress was investigated in our study. No significant decrease in thiol-related antioxidant capacity and an increase in the level of ischemia-modified albumin (IMA), the oxidant marker, were observed. The absence of the expected change led to the assumption that the main change after ischemia-reperfusion occurred in the precursor molecules that we could not measure, or that a different oxidant-antioxidant system was effective. Empagliflozin may have exerted its suppressive effect on inflammation and apoptosis in acute lung injury through inhibition of sodium-hydrogen exchange at the cellular level, ketone oxidation, and SGLT receptor inhibition, which have been proven as cardiorenal protective mechanisms in previous studies. It may have exerted its antioxidant effect at the tissue level that we could not measure, or through another system.
We conclude that empagliflozin therapy causes morphologic improvement in acute lung injury in rats after intestinal I/R injury. We believe that further preclinical research into the utility of empagliflozin may indicate its usefulness as a potential treatment for pulmonary damage after intestinal I/R injury in rats