Linagliptin Ameliorates Methylglyoxal-Induced Peritoneal Fibrosis in Mice

Linagliptin mitigates lipopolysaccharide-induced acute kidney injury in mice: Novel renal BDNF/TrkB/NRF2-dependent antioxidant, anti-inflammatory, and antiapoptotic mechanisms

Acute kidney injury (AKI) is a common complication associated with sepsis, yet no effective treatment is currently available. The primary mechanisms involved in lipopolysaccharide (LPS)-induced septic AKI are oxidative stress, inflammation, and apoptosis. This study aimed to investigate the potential renoprotective effects of linagliptin, an antidiabetic dipeptidyl peptidase (DPP)-4 inhibitor, against LPS-induced AKI with special emphasis on renal brain-derived neurotrophic factor (BDNF)/nuclear factor erythroid 2-related factor 2 (NRF2) axis. Mice were divided into control, LPS, LPS + linagliptin, and LPS + linagliptin+ANA-12 (tropomyosin receptor kinase B (TrkB) antagonist) groups. Our results revealed that linagliptin, partially through BDNF augmentation, ameliorated AKI, evidenced by the improved histological structure and function of the kidney where serum creatinine, blood urea nitrogen, cystatin C, and renal kidney injury molecule-1were decreased with increased serum albumin. These improvements result from glucagon-like peptide-1/BDNF/TrkB-mediated NRF2 activation, enhancing antioxidant, anti-inflammatory, and antiapoptotic pathways. Linagliptin, through NRF2 augmentation, suppressed renal myeloperoxidase, malondialdehyde, NLR Family pyrin domain-containing 3 inflammasome, nuclear factor-kappaB, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, B-cell lymphoma 2 (Bcl2)-associated X protein, while boosting the antioxidant glutathione and the antiapoptotic Bcl2 contents. The administration of ANA-12 before linagliptin partially reversed these beneficial effects. Accordingly, our results suggest that linagliptin has therapeutic potential in managing LPS-induced AKI. Furthermore, they provide insights into its underlying mechanisms, highlighting renal BDNF signaling as a potential therapeutic target through downstream NRF2 enhancement and its associated antioxidant, anti-inflammatory, and antiapoptotic effects.

Targeting MLL1/WDR5-Mediated Epigenetic Regulation Mitigates Peritoneal Fibrosis by Reducing p16INK4a

Peritoneal fibrosis poses a significant challenge to the long-term efficacy of peritoneal dialysis (PD), with emerging evidence highlighting the role of cellular senescence in its pathogenesis. p16INK4a is a cell cycle regulator that has been implicated in cellular senescence. Mixed-lineage leukemia 1 (MLL1) forms a complex with WD-40 repeat protein 5 (WDR5) and exhibits histone H3K4 methyltransferase activity. We have previously shown that inhibition of the MLL1/WDR5 complex reduces p16INK4a expression and attenuates renal senescence after injury in mice. This study aimed to investigate whether inhibiting MLL1/WDR5 attenuates peritoneal senescence, inflammation, and fibrosis in both human samples and in mice with methylglyoxal (MGO)-induced peritoneal fibrosis (MGO-injected mice), while also exploring the associated underlying mechanisms. MLL1/WDR5, histone 3 lysine 4 trimethylation (H3K4me3), and p16INK4a expression were elevated in TGF-β1-stimulated human peritoneal mesothelial cells (HPMCs), non-adherent cells obtained from patients undergoing PD, and the submesothelial compact zones of MGO-injected mice. Notably, p16INK4a expression in these cells was positively correlated with the dialysate/plasma creatinine ratio. Treatment with the MLL1/WDR5 protein-protein interaction inhibitors MM-102 and OICR-9429 reduced H3K4me3 levels and p16INK4a expression, suppressing fibrosis in HPMCs as well as peritoneal fibrosis and inflammation in MGO-injected mice. These inhibitors also improved peritoneal function in MGO-injected mice. Additionally, we demonstrated that MLL1/WDR5-induced H3K4me3 directly regulates p16INK4a gene transcription, and that inhibiting MLL1/WDR5 reduces H3K4me3, thereby suppressing p16INK4a gene transcription. These findings suggest that targeting MLL1/WDR5 activation alleviates peritoneal senescence, inflammation, and fibrosis, highlighting its potential as a promising therapeutic strategy for peritoneal fibrosis.

Mechanisms underlying the involvement of peritoneal macrophages in the pathogenesis and novel therapeutic strategies for dialysis-induced peritoneal fibrosis

Long-term exposure of the peritoneum to peritoneal dialysate results in pathophysiological changes in the anatomical organization of the peritoneum and progressive development of peritoneal fibrosis. This leads to a decline in peritoneal function and ultrafiltration failure, ultimately necessitating the discontinuation of peritoneal dialysis, severely limiting the potential for long-term maintenance. Additionally, encapsulating peritoneal sclerosis, a serious consequence of peritoneal fibrosis, resulting in patients discontinuing PD and significant mortality. The causes and mechanisms underlying peritoneal fibrosis in patients undergoing peritoneal dialysis remain unknown, with no definitive treatment available. However, abnormal activation of the immune system appears to be involved in altering the structure of the peritoneum and promoting fibrotic changes. Macrophage infiltration and polarization are key contributors to pathological injury within the peritoneum, showing a strong correlation with the epithelial-to-mesenchymal transition of mesothelial cells and driving the process of fibrosis. This article discusses the role and mechanisms underlying macrophage activation-induced peritoneal fibrosis resulting from PD by analyzing relevant literature from the past decade and provides an overview of recent therapeutic approaches targeting macrophages to treat this condition.

Effects of sitagliptin on peritoneal membrane: The potential role of mesothelial cell tight junction proteins

BACKGROUND

The roles of tight junction (TJ) proteins in peritoneal membrane transport and peritoneal dialysis (PD) require further characterisation. Dipeptidyl peptidase-4 is expressed in mesothelial cells, and its activity may affect peritoneal membrane function and morphology.

METHODS

Human peritoneal mesothelial cells (HPMCs) were isolated and cultured from omentum obtained during abdominal surgery, and paracellular transport functions were evaluated by measuring transmesothelial electrical resistance (TMER) and dextran flux. Sprague-Dawley rats were infused daily with 4.25% peritoneal dialysate with and without sitagliptin administration for 8 weeks. At the end of this period, rat peritoneal mesothelial cells (RPMCs) were isolated to evaluate TJ protein expression.

RESULTS

In HPMCs, the protein expression of claudin-1, claudin-15, occludin and E-cadherin was decreased by TGF-β treatment but reversed by sitagliptin co-treatment. TMER was decreased by TGF-β treatment but improved by sitagliptin co-treatment. Consistent with this, dextran flux was increased by TGF-β treatment and reversed by sitagliptin co-treatment. In the animal experiment, sitagliptin-treated rats had a lower D2/D0 glucose ratio and a higher D2/P2 creatinine ratio than PD controls during the peritoneal equilibration test. Protein expression of claudin-1, claudin-15 and E-cadherin decreased in RPMCs from PD controls but was not affected in those from sitagliptin-treated rats. Peritoneal fibrosis was induced in PD controls but ameliorated in sitagliptin-treated rats.

CONCLUSION

The expression of TJ proteins including claudin-1 and claudin-15 was associated with transport function both in HPMCs and in a rat model of PD. Sitagliptin prevents peritoneal fibrosis in PD and can potentially restore peritoneal mesothelial cell TJ proteins.

Importance of Fibrosis in the Pathogenesis of Uterine Leiomyoma and the Promising Anti-fibrotic Effects of Dipeptidyl Peptidase-4 and Fibroblast Activation Protein Inhibitors in the Treatment of Uterine Leiomyoma

Uterine fibroid or leiomyoma is the most common benign uterus tumor. The tumor is primarily composed of smooth muscle (fibroid) cells, myofibroblast, and a significant amount of extracellular matrix components. It mainly affects women of reproductive age. They are uncommon before menarche and usually disappear after menopause. The fibroids have excessive extracellular matrix components secreted by activated fibroblast cells (myofibroblast). Myofibroblast has the characteristics of fibroblast and smooth muscle cells. These cells possess contractile capability due to the expression of contractile proteins which are normally found only in muscle tissues. The rigid nature of the tumor is responsible for many side effects associated with uterine fibroids. The current drug treatment strategies are primarily hormone-driven and not anti-fibrotic. This paper emphasizes the fibrotic background of uterine fibroids and the mechanisms behind the deposition of excessive extracellular matrix components. The transforming growth factor-β, hippo, and focal adhesion kinase-mediated signaling pathways activate the fibroblast cells and deposit excessive extracellular matrix materials. We also exemplify how dipeptidyl peptidase-4 and fibroblast activation protein inhibitors could be beneficial in reducing the fibrotic process in leiomyoma. Dipeptidyl peptidase-4 and fibroblast activation protein inhibitors prevent the fibrotic process in organs such as the kidneys, lungs, liver, and heart. These inhibitors are proven to inhibit the signaling pathways mentioned above at various stages of their activation. Based on literature evidence, we constructed a narrative review on the mechanisms that support the beneficial effects of dipeptidyl peptidase-4 and fibroblast activation protein inhibitors for treating uterine fibroids.

Hepatocyte growth factor ameliorates methylglyoxal-induced peritoneal inflammation and fibrosis in mouse model

BACKGROUND

Peritoneal dialysis (PD) is essential for patients with end-stage renal disease. Peritoneal fibrosis (PF) is a complex inflammatory, fibrogenic process. No effective treatments are available to prevent these processes. Hepatocyte growth factor (HGF) possesses anti-inflammatory and anti-fibrotic properties. The aim of this study was to analyze whether HGF suppresses MGO-induced peritoneal inflammation and fibrosis in a mouse model.

METHODS

PF was induced by intraperitoneal (IP) injections of MGO for 14 days. C57/BL/6 mice were divided into three groups: Sham group (only vehicle); Sham + MGO group (PF induced by MGO); and HGF + MGO group (PF mice treated with recombinant human-HGF). PF was assessed from tissue samples by Masson's trichrome staining. Inflammation and fibrosis-associated factors were assessed by immunohistochemistry and quantitative real-time PCR.

RESULTS

MGO-injected mice showed significant thickening of the submesothelial compact zone with PF. Treatment with HGF significantly reduced PM thickness and suppressed the expression of collagen I and III and α-SMA. Expression of profibrotic and proinflammatory cytokines (TGF-β, TNF-α, IL-1β) was reduced by HGF treatment. The number of macrophages, and M1 and M2 macrophage-related markers, such as CD86, CD206, and CD163, was reduced in HGF + MGO mice.

CONCLUSION

HGF attenuates MGO-induced PF in mice. Furthermore, HGF treatment reduces myofibroblast and macrophage infiltration, and attenuates the upregulated expression of proinflammatory and profibrotic genes in peritoneal tissues. HGF might be an effective approach to prevent the development of PF in patients undergoing PD.

Dipeptidyl peptidase 4 promotes peritoneal fibrosis and its inhibitions prevent failure of peritoneal dialysis

Peritoneal dialysis (PD) possesses multiple advantages for end stage renal disease. However, long-term PD triggers peritoneal fibrosis (PF). From the nationwide analysis of diabetic PD patients (n = 19,828), we identified the incidence of PD failure was significantly lower in diabetic patients treated with dipeptidyl peptidase 4 (DPP4) inhibitors. Experimental study further showed high concentration of glucose remarkably enhanced DPP4 to promote epithelial-mesenchymal transition (EMT) in the mesothelial cells. In chlorhexidine gluconate (CG)-induced PF model of rats, DPP4 expression was enriched at thickening peritoneum. Moreover, as to CG-induced PF model, DPP4 deficiency (F344/DuCrlCrlj strain), sitagliptin and exendin-4 treatments significantly inhibited DPP4 to reverse the EMT process, angiogenesis, oxidative stress, and inflammation, resulting in the protection from PF, preservation of peritoneum and the corresponding functional integrity. Furthermore, DPP4 activity was significantly correlated with peritoneal dysfunction. Taken together, DPP4 caused peritoneal dysfunction/PF, whereas inhibition of DPP4 protected the PD patients against PD failure.

Hepatoprotective effect of linagliptin against liver fibrosis induced by carbon tetrachloride in mice

The current study aimed to investigate linagliptin for its potential role in the prevention of liver fibrosis progression. Balb-C mice were randomly allocated into five groups (10 each): (i) control; (ii) mice were injected intraperitoneally with 50 μL carbon tetrachloride (CCl₄) in corn oil in a dose of 0.6 μL/g three times per week for four weeks; (iii) linagliptin was administered orally in a daily dose of 10 mg/kg simultaneously with CCl₄; (iv) silymarin was administered orally in a daily dose of 200 mg/kg concomitantly with CCl₄; and (v) only linagliptin was administered. Hepatic injury was manifested in the CCl₄ group by elevation of biochemical parameters (alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP)), and hepatic fibrosis was evident histopathologically by increased METAVIR score and immunostaining expression of alpha-smooth muscle actin (α-SMA), as well as increased liver tissue oxidative stress parameters, transforming growth factor-β1 (TGF-β1), and mammalian target of rapamycin (mTOR). Linagliptin was able to stop the progression of liver fibrosis, evident histopathologically with reduced METAVIR score and α-SMA expression. The possible mechanism may be via suppression of oxidative stress, TGF-β1, and mTOR, which was associated with improvement of serum biochemical parameters ALT and AST. In conclusion, linagliptin might help to protect the liver against persistent injury-related consequences.

Inhibition of the H3K4 methyltransferase SET7/9 ameliorates peritoneal fibrosis

Transforming growth factor-β1 (TGF-β1) is a major mediator of peritoneal fibrosis and reportedly affects expression of the H3K4 methyltransferase, SET7/9. SET7/9-induced H3K4 mono-methylation (H3K4me1) critically activates transcription of fibrosis-related genes. In this study, we examined the effect of SET7/9 inhibition on peritoneal fibrosis in mice and in human peritoneal mesothelial cells (HPMCs). We also examined SET7/9 expression in nonadherent cells isolated from the effluent of peritoneal dialysis (PD) patients. Murine peritoneal fibrosis was induced by intraperitoneal injection of methylglyoxal (MGO) into male C57/BL6 mice over 21 days. Sinefungin, a SET7/9 inhibitor, was administered subcutaneously just before MGO injection (10 mg/kg). SET7/9 expression was elevated in both MGO-injected mice and nonadherent cells isolated from the effluent of PD patients. SET7/9 expression was positively correlated with dialysate/plasma ratio of creatinine in PD patients. Sinefungin was shown immunohistochemically to suppress expression of mesenchymal cells and collagen deposition, accompanied by decreased H3K4me1 levels. Peritoneal equilibration tests showed that sinefungin attenuated the urea nitrogen transport rate from plasma and the glucose absorption rate from the dialysate. In vitro, sinefungin suppressed TGF-β1-induced expression of fibrotic markers and inhibited H3K4me1. These findings suggest that inhibiting the H3K4 methyltransferase SET7/9 ameliorates peritoneal fibrosis.

Linagliptin potentiates the effect of l-dopa on the behavioural, biochemical and immunohistochemical changes in experimentally-induced Parkinsonism: Role of toll-like receptor 4, TGF-β1, NF-κB and glucagon-like peptide 1

OBJECTIVE

Our aim was to assess the effect of different doses of linagliptin with or without l-dopa/Carbidopa on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism in mice.

METHODS

Eighty Balb/c mice were divided into 8 equal groups: Control; MPTP; MPTP + l-dopa/Carbidopa; MPTP + linagliptin 3 mg/kg/day; MPTP + linagliptin 10 mg/kg/day; MPTP + Carboxymethyl cellulose; MPTP + l-dopa/Carbidopa + linagliptin 3 mg/kg/day and MPTP + l-dopa/Carbidopa + linagliptin 10 mg/kg/day. Striatal dopamine, tumor necrosis factor alpha (TNF-α), interleukin 10 (IL-10), transforming growth factor beta 1 (TGF-β1), toll-like receptor 4 (TLR4), antioxidant enzymes, adenosine triphosphate (ATP), glucagon-like peptide-1 (GLP-1), receptors of advanced glycation end products (RAGE), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), heme oxygenase-1 (HO-1), mitochondrial complex I activity, catalepsy and total swim scores were measured. Also, the substantia nigra was subjected to immunohistochemical examination.

RESULTS

The combination of l-dopa/Carbidopa and linagliptin in a dose-dependent manner resulted in significant improvement of the behavioural changes, striatal dopamine, antioxidant parameters, Nrf2/HO-1 content, GLP-1, ATP and mitochondrial complex I activity with significant decrease in striatal RAGE, TGF-β1, TNF-α, IL-10, TLR4 and alleviated the immunohistochemical changes better than the groups that received either l-dopa/Carbidopa or linagliptin alone.

CONCLUSION

The combination of l-dopa/Carbidopa and linagliptin might represent a promising therapeutic modality for management of parkinsonism.

The role of renal dipeptidyl peptidase-4 in kidney disease: renal effects of dipeptidyl peptidase-4 inhibitors with a focus on linagliptin

Emerging evidence suggests that dipeptidyl peptidase-4 (DPP-4) inhibitors used to treat type 2 diabetes may have nephroprotective effects beyond the reduced renal risk conferred by glycemic control. DPP-4 is a ubiquitous protein with exopeptidase activity that exists in cell membrane-bound and soluble forms. The kidneys contain the highest levels of DPP-4, which is increased in diabetic nephropathy. DPP-4 inhibitors are a chemically heterogeneous class of drugs with important pharmacological differences. Of the globally marketed DPP-4 inhibitors, linagliptin is of particular interest for diabetic nephropathy as it is the only compound that is not predominantly excreted in the urine. Linagliptin is also the most potent DPP-4 inhibitor, has the highest affinity for this protein, and has the largest volume of distribution; these properties allow linagliptin to penetrate kidney tissue and tightly bind resident DPP-4. In animal models of kidney disease, linagliptin elicited multiple renoprotective effects, including reducing albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis, independent of changes in glucagon-like peptide-1 (GLP-1) and glucose levels. At the molecular level, linagliptin prevented the pro-fibrotic endothelial-to-mesenchymal transition by disrupting the interaction between membrane-bound DPP-4 and integrin β1 that enhances signaling by transforming growth factor-β1 and vascular endothelial growth factor receptor-1. Linagliptin also increased stromal cell derived factor-1 levels, ameliorated endothelial dysfunction, and displayed unique antioxidant effects. Although the nephroprotective effects of linagliptin are yet to be translated to the clinical setting, the ongoing Cardiovascular and Renal Microvascular Outcome Study with Linagliptin in Patients with Type 2 Diabetes Mellitus (CARMELINA®) study will definitively assess the renal effects of this DPP-4 inhibitor. CARMELINA® is the only clinical trial of a DPP-4 inhibitor powered to evaluate kidney outcomes.

RETRACTED: Ameliorative potential of linagliptin and/or calcipotriol on bleomycin-induced lung fibrosis: In vivo and in vitro study

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted due to the authors’ plagiarism of text and images from the work of Eman Said Abd-Elkhalek, Hatem Abdel-Rahman Salem, Ghada Mohamed SuddeK, Marwa Ahmed Zaghloul and Ramy Ahmed Abdel-Salam, Faculties of Pharmacy and Medicine, Mansoura University, Mansoura, Egypt.