Protective role of sitagliptin against oxidative stress in a kainic acid-induced status epilepticus in rats models via Nrf2/HO-1 pathway

The many facets of CD26/dipeptidyl peptidase 4 and its inhibitors in disorders of the CNS - a critical overview

Dipeptidyl peptidase 4 is a serine protease that cleaves X-proline or X-alanine in the penultimate position. Natural substrates of the enzyme are glucagon-like peptide-1, glucagon inhibiting peptide, glucagon, neuropeptide Y, secretin, substance P, pituitary adenylate cyclase-activating polypeptide, endorphins, endomorphins, brain natriuretic peptide, beta-melanocyte stimulating hormone and amyloid peptides as well as some cytokines and chemokines. The enzyme is involved in the maintenance of blood glucose homeostasis and regulation of the immune system. It is expressed in many organs including the brain. DPP4 activity may be effectively depressed by DPP4 inhibitors. Apart from enzyme activity, DPP4 acts as a cell surface (co)receptor, associates with adeosine deaminase, interacts with extracellular matrix, and controls cell migration and differentiation. This review aims at revealing the impact of DPP4 and DPP4 inhibitors for several brain diseases (virus infections affecting the brain, tumours of the CNS, neurological and psychiatric disorders). Special emphasis is given to a possible involvement of DPP4 expressed in the brain.While prominent contributions of extracerebral DPP4 are evident for a majority of diseases discussed herein; a possible role of "brain" DPP4 is restricted to brain cancers and Alzheimer disease. For a number of diseases (Covid-19 infection, type 2 diabetes, Alzheimer disease, vascular dementia, Parkinson disease, Huntington disease, multiple sclerosis, stroke, and epilepsy), use of DPP4 inhibitors has been shown to have a disease-mitigating effect. However, these beneficial effects should mostly be attributed to the depression of "peripheral" DPP4, since currently used DPP4 inhibitors are not able to pass through the intact blood-brain barrier.

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.

Saxagliptin protects against hypoxia-induced damage in H9c2 cells

Type II diabetes is recognized as a major risk factor for death due to cardiovascular complications such as coronary heart disease (CHD), but the complex interplay between these two diseases remains poorly understood. Suppression of oxidative stress, apoptosis, and inflammation of endothelial cells is a valuable treatment strategy to prevent or halt the progression of CHD. In the present study, we used real-time polymerase chain reaction (PCR), Western blot analysis, and enzyme linked immunosorbent assay (ELISA) to investigate the effects of saxagliptin on hypoxia-inducible factors. Our findings demonstrate that saxagliptin can significantly improve cell viability in H9c2 cells as well as reduce hypoxia-induced oxidative damage and loss of mitochondrial membrane potential. Saxagliptin reduced hypoxia-induced NADPH oxidase 4 (NOX 4). We also show that saxagliptin can reduce the expression of matrix metallopeptidase-2 (MMP-2) and matrix metallopeptidase-9 (MMP-9), two important degradative enzymes. Saxagliptin also suppressed hypoxia-induced expression of high mobility group box-1 protein (HMGB1), a key inflammatory cytokine. Finally, we show that saxagliptin can exert atheroprotective effects by reducing the expression of myeloid differential protein-88 (MyD88) and increasing the expression of nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Thus, saxagliptin shows promise as a treatment against diabetes-associated CHD.