Profibrotic mechanisms of DPP8 and DPP9 highly expressed in the proximal renal tubule epithelial cells

Huangqi-Danshen Decoction Against Renal Fibrosis in UUO Mice via TGF-β1 Induced Downstream Signaling Pathway

Background

Huangqi-Danshen decoction (HDD) is a Chinese medicinal herb pair with good efficacy in treating chronic kidney disease, but its mechanism needs to be clarified.

Aim

To uncover the underlying mechanism of HDD antagonizing renal fibrosis through network pharmacology (NP) analysis and experimental validation.

Materials and Methods

The chemical components of water extract of HDD were analyzed by combining the ultra-high performance liquid chromatography coupled with Q-Exactive mass spectrum analysis (UHPLC-QE-MS) and HERB database. NP was used to identify core common targets of HDD components and renal fibrosis. Subsequently, male C57BL/6 mice were divided into Sham, unilateral ureteral obstruction (UUO) and UUO+HDD groups. Renal function, histopathology, Western blotting, and immunohistochemistry analyses were used to evaluate the protective effect of HDD on UUO mice. The effects of HDD on signaling pathways were validated in both UUO mice and transforming growth factor-β1 (TGF-β1)-induced HK-2 cells.

Results

By combining UHPLC-QE-MS analysis and HERB database, 25 components were screened in HDD extract. There were 270 intersection targets of the 25 components and renal fibrosis. Based on their scores in protein-protein interaction analysis and degree values in component-pathway-target triadic network, 6 core common targets of the 25 components and renal fibrosis were identified, namely phosphoinositide 3-kinase (PI3K), signal transducer and activator of transcription 3 (Stat3), non-receptor tyrosine kinase Src (Src), epidermal growth factor receptor (EGFR), matrix metalloproteinase 9 (MMP9), and MMP2. HDD ameliorated renal tubular damage and collagen deposition and downregulated fibrosis-related proteins expression in UUO mice. Furthermore, HDD was demonstrated to reduce PI3K, Stat3, Src, EGFR, and MMP2 expressions, and enhance MMP9 expression in the kidney of UUO mice and in TGF-β1-induced HK-2 cells.

Conclusion

HDD can alleviate renal fibrosis which may be related to regulating the expression of essential proteins in the epithelial-mesenchymal transition and extracellular matrix production/degradation signaling pathways.

Unravelling the role of dipeptidyl peptidases-8/9 (DPP-8/9) in inflammatory osteoporosis: a comprehensive study investigating chrysin as a potential anti-osteoporotic agent

OBJECTIVES

This study aimed to investigate the role of dipeptidyl peptidase-8 and 9 (DPP-8/9) enzymes in inflammatory bone loss using a 4-vinylcyclohexene diepoxide (VCD)-induced model in Wistar rats. Additionally, we evaluated the therapeutic potential of inhibiting these enzymes with the flavonoid chrysin.

METHODS

Inflammatory osteoporosis was induced by administering VCD that elevated interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) levels. DPP-8/9 enzyme expression and various bone markers were assayed using serum. Further analysis included bone microarchitecture, histology, and immunohistochemistry. Additionally, chrysin's potential to inhibit DPP-8/9 and mitigate VCD-induced inflammatory bone loss was also evaluated.

KEY FINDINGS

VCD administration in rats caused ovotoxicity that increased IL-6 and TNF-α levels, resulting in significant bone loss. Serum analysis revealed elevated bone resorption markers and DPP-8/9 enzyme levels. Inhibiting DPP-8/9 with 1G244 reversed these effects, confirmed by histology, immunohistochemistry, and micro-CT scans. Moreover, chrysin significantly reduced DPP-8/9 levels compared with the untreated group, improved bone markers, and lower inflammatory cytokines, indicating reduced osteoclastogenesis.

CONCLUSION

This study highlights the role of DPP-8/9 in inflammation-induced osteoporosis. Following inhibition of DPP-8/9, we observed improved bone markers with preservation of trabecular bone mineral density in rats. Additionally, chrysin demonstrated potential as an anti-DPP-8/9 agent, suggesting its viability for future therapeutic interventions in DPP-8/9-related inflammatory diseases.

WIP1-mediated regulation of p38 MAPK signaling attenuates pyroptosis in sepsis-associated acute kidney injury

Wild-Type p53-Induced Phosphatase 1 (WIP1/PPM1D) is a serine/threonine phosphatase that plays a significant role in various physiological processes. However, the involvement of WIP1 in kidney remains unclear. Lipopolysaccharide (LPS) was administered to induce acute injury in mice and human kidney 2 (HK2) cells in the study. The WIP1 inhibitor, CCT007093, was administered both in vitro and in vivo to assess its effect on kidney. The single-cell sequencing (scRNA-seq) data revealed that Ppm1d mRNA reached peak on day 2 following unilateral ischemia-reperfusion injury (uni-IRI) in mice, especially in the proximal renal tubules during repair phase. Compared to the control group, WIP1 protein exhibited a significant increase in renal tubules of patients with acute tubular injury (ATI) and mice with LPS-induced acute kidney injury (AKI), as well as in LPS-injured HK2 cells. In vitro experiments showed that CCT007093 increased the protein levels of NLRP3, cleaved-Caspase1, GSDMD-N and IL-1β in HK2 cells and further reduced the viability of LPS-stimulated HK2 cells. In vivo experiments showed that inhibition of WIP1 activity with CCT007093 further increased cleaved-Caspase1, GSDMD-N protein levels in kidney tissue from mice with LPS-induced AKI. In addition, LPS induces phosphorylation of p38 MAPK, a key regulator of pyroptosis, which is further activated by CCT007093. In conclusion, inhibition of WIP1 activity acts as a positive regulator of renal tubular pyroptosis mainly through the mediation of phospho-p38 MAPK.

DPP8/9 inhibition attenuates the TGF-β1-induced excessive deposition of extracellular matrix (ECM) in human mesangial cells via Smad and Akt signaling pathways

The pathogenesis of glomerular diseases is strongly influenced by abnormal extracellular matrix (ECM) deposition in mesangial cells. Dipeptidyl peptidase IV (DPPIV) enzyme family contains DPP8 and DPP9, which are involved in multiple diseases. However, the pathogenic roles of DPP8 and DPP9 in mesangial cells ECM deposition remain unclear. In this study, we observed that DPP8 and DPP9 were significantly increased in glomerular mesangial cells and podocytes in CKD patients compared with healthy individuals, and DPP9 levels were higher in the urine of IgA nephropathy (IgAN) patients than in control urine. Therefore, we further explored the mechanism of DPP8 and DPP9 in mesangial cells and revealed a significant increase in the expression of DPP8 and DPP9 in human mesangial cells (HMCs) following TGF-β1 stimulation. Silencing DPP8 and DPP9 by siRNAs alleviated the expression of ECM-related proteins including collagen Ⅲ, collagen Ⅳ, fibronectin, MMP2, in TGF-β1-treated HMCs. Furthermore, DPP8 siRNA and DPP9 siRNA inhibited TGF-β1-induced phosphorylation of Smad2 and Smad3, as well as the phosphorylation of Akt in HMCs. The findings suggested the inhibition of DPP8/9 may alleviate HMCs ECM deposition induced by TGF-β1 via suppressing TGF-β1/Smad and AKT signaling pathways.

New insights into the role of dipeptidyl peptidase 8 and dipeptidyl peptidase 9 and their inhibitors

Dipeptidyl peptidase 8 (DPP8) and 9 (DPP9) are widely expressed in mammals including humans, mainly locate in the cytoplasm. The DPP8 and DPP9 (DPP8/9) belong to serine proteolytic enzymes, they can recognize and cleave N-terminal dipeptides of specific substrates if proline is at the penultimate position. Because the localization of DPP8/9 is different from that of DPP4 and the substrates for DPP8/9 are not yet completely clear, their physiological and pathological roles are still being further explored. In this article, we will review the recent research advances focusing on the expression, regulation, and functions of DPP8/9 in physiology and pathology status. Emerging research results have shown that DPP8/9 is involved in various biological processes such as cell behavior, energy metabolism, and immune regulation, which plays an essential role in maintaining normal development and physiological functions of the body. DPP8/9 is also involved in pathological processes such as tumorigenesis, inflammation, and organ fibrosis. In recent years, related research on immune cell pyroptosis has made DPP8/9 a new potential target for the treatment of hematological diseases. In addition, DPP8/9 inhibitors also have great potential in the treatment of tumors and chronic kidney disease.

The sugar daddy: the role of the renal proximal tubule in glucose homeostasis

Renal blood flow represents >20% of total cardiac output and with this comes the great responsibility of maintaining homeostasis through the intricate regulation of solute handling. Through the processes of filtration, reabsorption, and secretion, the kidneys ensure that solutes and other small molecules are either returned to circulation, catabolized within renal epithelial cells, or excreted through the process of urination. Although this occurs throughout the renal nephron, one segment is tasked with the bulk of solute reabsorption-the proximal tubule. Among others, the renal proximal tubule is entirely responsible for the reabsorption of glucose, a critical source of energy that fuels the body. In addition, it is the only other site of gluconeogenesis outside of the liver. When these processes go awry, pathophysiological conditions such as diabetes and acidosis result. In this review, we highlight the recent advances made in understanding these processes that occur within the renal proximal tubule. We focus on the physiological mechanisms at play regarding glucose reabsorption and glucose metabolism, emphasize the conditions that occur under diseased states, and explore the emerging class of therapeutics that are responsible for restoring homeostasis.

Inhibitory Effects of Rhein on Renal Interstitial Fibrosis via the SHH-Gli1 Signal Pathway

Background. Rhein is the main extract of Rheum palmatum L., which has been proved to improve the renal function of chronic kidney disease, but its mechanism is not clear. Therefore, this experiment explored the potential pharmacological effect of rhein on renal interstitial fibrosis rats. Methods. This study explores the potential pharmacological action of rhein. In this work, we investigate the potential pharmacological action of rhein in unilateral urethral obstruction (UUO) rats. Thirty Sprague Dawley rats were randomly divided into three groups: sham, UUO, and rhein (rhein-treated UUO rats) groups. The left ureters of the UUO group rats were exposed and bluntly dissected. The rhein group rats were administered an intragastric gavage of rhein (2 mg·kg−1·d−1) for 14 d. Kidney function-related indicators were monitored in these rats, while indexes of pathologic aspects were determined histologically. The expression of α-SMA, TGF-β1, SHH, Gli1, and Snail was quantified using real-time polymerase chain reaction and western blotting. The NRK-49F cells were incubated with and without SHH (100 ng·ml−1) for 48 hours. The SHH-activated NRK-49F cells were incubated with cyclopamine (CNP, 20 umol L−1) or rhein (1 ng·ml−1). The Gli1 and Snail mRNA and protein level were detected. Results. In the in vivo experiment, the results exhibited that UUO caused renal pathological damages. However, these changes could be significantly reversed by the administration of rhein. Compared with the untreated UUO group, the rhein group showed reduced kidney tubular atrophy and necrosis, interstitial fibrosis, hyperplasia, and abnormal deposition of extracellular matrix. Rhein reduced the RNA and protein expression of SHH, Gli1, and Snail of the UUO rats. In the in vitro experiment, CNP or rhein treatment decreased the expression of Gli1 and Snail on mRNA and protein levels in SHH-induced NRK-49F cells, suggesting that CNP or rhein suppresses SHH-induced NRK-49F activation. Taken together, these results demonstrated that rhein suppresses SHH-Gli1-Snail signal pathway activation, with potential implications for the treatment of renal fibrosis. Conclusions. Treatment with rhein remarkably ameliorated renal interstitial fibrosis in UUO rats by regulating the SHH-Gli1-Snail signal pathway.

Dipeptidyl Peptidase Inhibition Enhances CD8 T Cell Recruitment and Activates Intrahepatic Inflammasome in a Murine Model of Hepatocellular Carcinoma

Simple Summary

This study reported, for the first time, on the expression and activity of the dipeptidyl peptidase 4 (DPP4) family during the development of hepatocellular carcinoma (HCC). We also demonstrated that the pan-DPP inhibitory compound ARI-4175 significantly reduced the number of macroscopic liver nodules in a mouse HCC model. ARI-4175 increased intrahepatic inflammatory cell infiltration, CD8⁺ T cell numbers and caspase-1-mediated inflammasome activation in the HCC-bearing liver. Thus, this study provides promising data on the efficacy of ARI-4175 in the treatment of early-stage HCC. Targeting the DPP4 family may be a novel and effective approach to promote anti-tumour immunity in HCC via caspase-1 activation.

Abstract

The mRNA expression of the dipeptidyl peptidase 4 (DPP4) gene family is highly upregulated in human hepatocellular carcinoma (HCC) and is associated with poor survival in HCC patients. Compounds that inhibit the DPP4 enzyme family, such as talabostat and ARI-4175, can mediate tumour regression by immune-mediated mechanisms that are believed to include NLRP1 activation. This study investigated the expression and activity of the DPP4 family during the development of HCC and evaluated the efficacy of ARI-4175 in the treatment of early HCC in mice. This first report on this enzyme family in HCC-bearing mice showed DPP9 upregulation in HCC, whereas intrahepatic DPP8/9 and DPP4 enzyme activity levels decreased with age. We demonstrated that ARI-4175 significantly lowered the total number of macroscopic liver nodules in these mice. In addition, ARI-4175 increased intrahepatic inflammatory cell infiltration, including CD8⁺ T cell numbers, into the HCC-bearing livers. Furthermore, ARI-4175 activated a critical component of the inflammasome pathway, caspase-1, in these HCC-bearing livers. This is the first evidence of caspase-1 activation by a pan-DPP inhibitor in the liver. Our data suggest that targeting the DPP4 enzyme family may be a novel and effective approach to promote anti-tumour immunity in HCC via caspase-1 activation.