Linagliptin counteracts rotenone's toxicity in non-diabetic rat model of Parkinson's disease: Insights into the neuroprotective roles of DJ-1, SIRT-1/Nrf-2 and implications of HIF1-α

Unravelling the mechanism by which vildagliptin and linagliptin inhibit pyroptosis in lung injury through the NLRP3 inflammatory pathway in type 1 diabetic rats

Diabetes mellitus (DM) represents a multifactorial condition linked to hyperglycemia, which, can lead to damage across multiple organs, including the lungs. Nod-like receptor protein-3 (NLRP3)- mediated pyroptosis could contribute to the onset of DM consequences. Several approaches have been established aimed to minimizing the complications associated with DM. Among these, linagliptin and vildagliptin, di-peptidyl peptidase-4 (DPP-4) inhibitors, are known to exert not only antihyperglycemic effects but also additional beneficial biological activities. The current study investigated the impact of linagliptin and vildagliptin on pulmonary function, oxidative stress, and NLRP3-induced pyroptosis in rats. Thirty-two male Sprague Dawley rats were given a 7-day acclimatization period. A single intraperitoneal injection of freshly produced STZ (60 mg/kg) was utilized to develop DM type-1 in rats. Following STZ treatment, all rats were given a 5% glucose solution overnight. Blood glucose levels were monitored in overnight fasted rats 72 h later, with a threshold of 250 mg/dL or higher confirming the onset of DM. The diabetic rats were randomly allocated to treated daily with either vildagliptin (5 mg/kg/p.o.) or linagliptin (5 mg/kg/p.o.) for 30 days. Additionally, the typical control group received merely the vehicle. The findings revealed that vildagliptin improves pulmonary dysfunctions associated with DM by restoring glucose homeostasis, insulin, redox marker levels, and inflammatory indices. Additionally, the NLRP3-pyroptosis-mediated IL-1β was suppressed. Vildagliptin has been shown to mitigate the detrimental effects of diabetes mellitus (DM) on the lungs, as evidenced by a reduction in pathological lung alterations and a decrease in Caspase 3 expression, which is indicative of immunohistochemical changes. In conclusion, pyroptosis triggered by the NLRP3 inflammasome possibly exacerbate diabetic pulmonary injury in rats. Vildagliptin is superior to linagliptin in ameliorating diabetes-induced lung injury primarily via targeting the NLRP3 inflammasome pathway.

Modulation of FOXO3a Nuclear Localization by Linagliptin (BI-1356) reveals a new therapeutic target in chronic ulcerative colitis

Globally, the incidence and prevalence rates of ulcerative colitis (UC) show a rising pattern. The limited efficacy and significant adverse effects associated with current treatment options underscore the need for novel therapeutic approaches. It has been found that linagliptin, a dipeptidyl peptidase-4 inhibitor, activates AMPK in different disease conditions. The main objective of the present work was to elucidate the potential implications of the AMPK/FOXO3a mediated by linagliptin in rats with chronic colitis. The findings of the current report revealed the first robust in-vivo evidence advocating the coloprotective effect of linagliptin against dextran sodium sulfate-induced chronic UC in rats. It has demonstrated potential beyond its antidiabetic effects by modulating FOXO3a localization. By shifting FOXO3a from the cytosol to the nucleus, linagliptin enhanced the transcription of genes involved in attenuation of pro-inflammatory events and restoration of redox homeostasis. Nuclear FOXO3a also impacted NFκB activity, reducing inflammation. This conclusion was fundamentally supported by the documented improvements in histopathological changes evidenced by reduced inflammation, edema, crypt atrophy, and submucosal fibrosis. Moreover, decreased colon weight/length ratio, as well as reduced scores of disease activity and macroscopic damage indices, were observed. Furthermore, it corrected body weight loss during the time frame of the experiment. These findings underscore the anti-inflammatory potential of therapies that promote the nuclear localization of FOXO3a in inflammatory conditions. Linagliptin's ability to modulate FOXO3a localization might be particularly useful for diabetic patients suffering from inflammatory bowel diseases. However, further molecular investigations are required to validate the findings and to assess the clinical application of this approach as a valid tool for alleviating UC.

Crosstalk between SIRT1/Nrf2 signaling and NLRP3 inflammasome/pyroptosis as a mechanistic approach for the neuroprotective effect of linagliptin in Parkinson's disease

In recent years, special attention has been paid to highlighting the antiparkinsonian effect of linagliptin. However, the mechanism of its action has not yet been well investigated. The present study aimed to verify the neuroprotective effect of linagliptin in the rotenone model of Parkinson's disease (PD) and further explore its potential molecular mechanisms. Rats were intoxicated with rotenone (2 mg/kg/day; sc) and treated with linagliptin (10  mg/kg/day; po) for 14 consecutive days. The present finding showed that linagliptin ameliorated the histopathological changes of rotenone on substantia nigra and striata. Linagliptin decreased α-synuclein immunoreactivity along with an increase in tyrosine hydroxylase immunoreactivity and striatal dopamine content. This was reflected in the marked improvement of the behavior and motor deficits in rotenone-intoxicated rats. On the molecular level, linagliptin upregulated sirtuin 1 (SIRT1)/ nuclear factor erythroid 2-related factor 2 (Nrf2) signaling, reduced ionized calcium-binding adaptor molecule 1 (Iba1) protein expression, restored glutathione (GSH) content, and elevated heme oxygenase-1 (HO-1) level in rats with rotenone intoxication. Moreover, linagliptin inhibited NOD-like receptor protein 3 (NLRP3)/caspase-1/interleukin-1β (IL-1β) cascade with subsequent reduction in gasdermin D (GSDMD) expression. Therefore, the present study reveals the ability of linagliptin, through the activation of SIRT1/Nrf2 signaling, to suppress NLRP3 inflammasome-mediated pyroptosis and protect against rotenone-induced parkinsonism.

Linagliptin ameliorates tacrolimus-induced renal injury: role of Nrf2/HO-1 and HIF-1α/CTGF/PAI-1

BACKGROUND

Tacrolimus (TAC) is a frequently used immunosuppressive medication in organ transplantation. However, its nephrotoxic impact limits its long-term usage. This study aims to investigate the effect of linagliptin (Lina) on TAC-induced renal injury and its underlying mechanisms.

METHODS AND RESULTS

Thirty-two Sprague Dawley rats were treated with TAC (1.5 mg/kg/day, subcutaneously) and/or Lina (5 mg/kg/day, orally) for 4 weeks. Histological examination was conducted, and serum and urinary biomarkers were measured to assess kidney function and integrity. Furthermore, ELISA, Western blot analysis and immunohistochemical assay were employed to determine signaling molecules of oxidative stress, profibrogenic, hypoxic, and apoptotic proteins. Tacrolimus caused renal dysfunction and histological deterioration evidenced by increased serum creatinine, blood urea nitrogen (BUN), urinary cystatin C, and decreased serum albumin as well as elevated tubular injury and interstitial fibrosis scores. Additionally, TAC significantly increased the expression of collagen type-1, alpha-smooth muscle actin (α-SMA), plasminogen activator inhibitor-1 (PAI-1), and transforming growth factor-beta1 (TGF-β1) renal content. Moreover, TAC decreased the expression of nuclear factor erythroid-2-related factor2 (Nrf2), heme oxygenase 1 (HO-1), and mitochondrial superoxide dismutase (SOD2). In addition, TAC increased protein expression of hypoxia-inducible factor1-alpha (HIF-1α), connective tissue growth factor (CTGF), inducible nitric oxide synthase (iNOS), 8-hydroxy-2-deoxyguanosine (8-OHdG), as well as nitric oxide (NO), 4-hydroxynonenal, caspase-3 and Bax renal contents. Furthermore, TAC decreased Bcl-2 renal contents. The Lina administration markedly attenuated these alterations.

CONCLUSION

Lina ameliorated TAC-induced kidney injury through modulation of oxidative stress, hypoxia, and apoptosis related proteins.

Neuroinflammation in Neurodegenerative Disorders: Current Knowledge and Therapeutic Implications

Neurodegenerative disorders (NDs) have become increasingly common during the past three decades. Approximately 15% of the total population of the world is affected by some form of NDs, resulting in physical and cognitive disability. The most common NDs include Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Although NDs are caused by a complex interaction of genetic, environmental, and lifestyle variables, neuroinflammation is known to be associated with all NDs, often leading to permanent damage to neurons of the central nervous system. Furthermore, numerous emerging pieces of evidence have demonstrated that inflammation not only supports the progression of NDs but can also serve as an initiator. Hence, various medicines capable of preventing or reducing neuroinflammation have been investigated as ND treatments. While anti-inflammatory medicine has shown promising benefits in several preclinical models, clinical outcomes are often questionable. In this review, we discuss various NDs with their current treatment strategies, the role of neuroinflammation in the pathophysiology of NDs, and the use of anti-inflammatory agents as a potential therapeutic option.

Acute and Chronic Exposure to Linagliptin, a Selective Inhibitor of Dipeptidyl Peptidase-4 (DPP-4), Has an Effect on Dopamine, Serotonin and Noradrenaline Level in the Striatum and Hippocampus of Rats

Linagliptin is a selective dipeptidyl peptidase-4 (DPP-4) inhibitor that indirectly elevates the glucagon-like peptide-1 (GLP-1) level. The aim of the present study was to check whether linagliptin has an influence on neurotransmission in rat brain. Rats were acutely and chronically exposed to linagliptin (10 and 20 mg/kg, intraperitoneally (i.p.)). Twenty-four hours later, the striatum and hippocampus were selected for further studies. In neurochemical experiments, using high-performance liquid chromatography with electrochemical detection (HPLC-ED), the concentrations of three major neurotransmitters-dopamine, serotonin and noradrenaline-and their metabolites were measured. The analysis of mRNA expression of dopamine (D1 and D2), serotonin (5-HT-1 and 5-HT-2) and noradrenaline (α1 and α2a) receptors was also investigated using real-time quantitative reverse transcription polymerase chain reaction (RQ-PCR) in the same brain areas. Linagliptin has the ability to influence the dopaminergic system. In the striatum, the elevation of dopamine and its metabolites was observed after repeated administration of that linagliptin, and in the hippocampus, a reduction in dopamine metabolism was demonstrated. Acute linagliptin exposure increases the serotonin level in both areas, while after chronic linagliptin administration a tendency for the mRNA expression of serotoninergic receptors (5-HT1A and 5-HT2A) to increase was observed. A single instance of exposure to linagliptin significantly modified the noradrenaline level in the striatum and intensified noradrenaline turnover in the hippocampus. The recognition of the interactions in the brain between DPP-4 inhibitors and neurotransmitters and/or receptors is a crucial step for finding novel discoveries in the pharmacology of DPP-4 inhibitors and raises hope for further applications of DPP-4 inhibitors in clinical practices.