The impact of sitagliptin, inhibitor of dipeptidyl peptidase-4 (DPP-4), on the ADMA-DDAH-NO pathway in ischemic and reperfused rat livers

Modulation of Prostanoids Profile and Counter-Regulation of SDF-1α/CXCR4 and VIP/VPAC2 Expression by Sitagliptin in Non-Diabetic Rat Model of Hepatic Ischemia-Reperfusion Injury

Molecular mechanisms underlying the beneficial effect of sitagliptin repurposed for hepatic ischemia-reperfusion injury (IRI) are poorly understood. We aimed to evaluate the impact of IRI and sitagliptin on the hepatic profile of eicosanoids (LC-MS/MS) and expression/concentration (RTqPCR/ELISA) of GLP-1/GLP-1R, SDF-1α/CXCR4 and VIP/VPAC1, VPAC2, and PAC1 in 36 rats. Animals were divided into four groups and subjected to ischemia (60 min) and reperfusion (24 h) with or without pretreatment with sitagliptin (5 mg/kg) (IR and SIR) or sham-operated with or without sitagliptin pretreatment (controls and sitagliptin). PGI₂, PGE₂, and 13,14-dihydro-PGE₁ were significantly upregulated in IR but not SIR, while sitagliptin upregulated PGD₂ and 15-deoxy-12,14-PGJ₂. IR and sitagliptin non-significantly upregulated GLP-1 while Glp1r expression was borderline detectable. VIP concentration and Vpac2 expression were downregulated in IR but not SIR, while Vpac1 was significantly downregulated solely in SIR. IRI upregulated both CXCR4 expression and concentration, and sitagliptin pretreatment abrogated receptor overexpression and downregulated Sdf1. In conclusion, hepatic IRI is accompanied by an elevation in proinflammatory prostanoids and overexpression of CXCR4, combined with downregulation of VIP/VPAC2. Beneficial effects of sitagliptin during hepatic IRI might be mediated by drug-induced normalization of proinflammatory prostanoids and upregulation of PGD₂ and by concomitant downregulation of SDF-1α/CXCR4 and reinstating VIP/VCAP2 signaling.

Sitagliptin Modulates Oxidative, Nitrative and Halogenative Stress and Inflammatory Response in Rat Model of Hepatic Ischemia-Reperfusion

A possibility of repurposing sitagliptin, a well-established antidiabetic drug, for alleviating injury caused by ischemia-reperfusion (IR) is being researched. The aim of this study was to shed some light on the molecular background of the protective activity of sitagliptin during hepatic IR. The expression and/or concentration of inflammation and oxidative stress-involved factors have been determined in rat liver homogenates using quantitative RT-PCR and Luminex^® xMAP^® technology and markers of nitrative and halogenative stress were quantified using targeted metabolomics (LC-MS/MS). Animals (n = 36) divided into four groups were treated with sitagliptin (5 mg/kg) (S and SIR) or saline solution (C and IR), and the livers from IR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). The midkine expression (by 2.2-fold) and the free 3-nitrotyrosine (by 2.5-fold) and IL-10 (by 2-fold) concentration were significantly higher and the Nox4 expression was lower (by 9.4-fold) in the IR than the C animals. As compared to IR, the SIR animals had a lower expression of interleukin-6 (by 4.2-fold) and midkine (by 2-fold), a lower concentration of 3-nitrotyrosine (by 2.5-fold) and a higher Nox4 (by 2.9-fold) and 3-bromotyrosine (by 1.4-fold). In conclusion, IR disturbs the oxidative, nitrative and halogenative balance and aggravates the inflammatory response in the liver, which can be attenuated by low doses of sitagliptin.

The hepatoprotective effect of sitagliptin against hepatic ischemia reperfusion-induced injury in rats involves Nrf-2/HO-1 pathway

BACKGROUND

Oxidative stress and inflammation play a key role in the development of hepatic ischemia reperfusion (HIR)-induced injury. Nuclear factor-erythroid 2-related factor-2 (Nrf-2) is a main regulator of numerous genes, encoding cytoprotective molecules including heme oxygenase-1 (HO-1). Sitagliptin (Sit) is an incretin enhancer acting via inhibition of dipeptidyl peptidase-4 (DPP-4) enzyme. This study was undertaken to investigate the ability of Sit to prevent the hepatic pathological changes of HIR induced injury and to modify Nrf-2 and its target HO-1.

METHODS

Pringle's maneuver was used to induce total HIR in adult male rats that were randomly assigned into 4 groups. Group1 (sham-operated control), Group 2 (sham-operated + Sit-control group), Group 3 (HIR non-treated), and Group 4 (HIR + Sit). Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities together with hepatic contents of malondialdhyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) and superoxide dismutase (SOD) activity were evaluated. Hepatic tissue mRNA of Nrf-2 and protein content of HO-1 along with histopathological examination and scoring of hepatic injury were performed.

RESULTS

Sit caused a significant reduction in ALT and AST activities together with attenuation of HIR-induced histopathological liver injury. Effect of Sit was associated with decreased hepatic level of MDA and NO with increased GSH level and SOD activity. Non-treated rats with HIR showed an increase in Nrf-2 mRNA expression and HO-1 content in hepatic tissue which was further increased by Sit treatment.

CONCLUSIONS

These results indicate that hepatoprotective activity of Sit against HIR is attributed at least in part to modulation of Nrf-2/ HO-1 signaling pathway.

Blueberry anthocyanin‑enriched extract ameliorates transverse aortic constriction‑induced myocardial dysfunction via the DDAH1/ADMA/NO signaling pathway in mice

Blueberry anthocyanin‑enriched extract (BAE) has been demonstrated to protect against cardiovascular diseases by activating multiple target genes. The present study investigated the effects of BAE on transverse aortic constriction (TAC)‑induced myocardial dysfunction in mice and explored its possible molecular mechanisms. A total of 30 male mice were divided randomly into control, TAC and TAC + BAE groups. Mice in the TAC + BAE groups were administered BAE by oral gavage for 6 consecutive weeks. Myocardial dysfunction was assessed using echocardiogram, histopathology, TUNEL assay, immunofluorescence staining, reverse transcription‑quantitative PCR and western blot analysis. The results demonstrated that BAE treatment significantly ameliorated heart weight, left ventricular weight, myocardial dysfunction, left ventricular hypertrophy and fibrosis. In addition, BAE treatment alleviated TAC‑induced inflammation, oxidative stress and apoptosis. Notably, BAE treatment markedly reduced asymmetric dimethylarginine (ADMA) concentration and significantly increased dimethylarginine dimethylaminohydrolase 1 (DDAH1) expression and nitric oxide (NO) production. The present data indicated that BAE treatment ameliorated TAC‑induced myocardial dysfunction, oxidative stress, inflammatory response and apoptosis via the DDAH1/ADMA/NO signaling pathway.