Protease-activated receptor 2 does not contribute to renal inflammation or fibrosis in the obstructed kidney

Par2-mediated responses in inflammation and regeneration: choosing between repair and damage

The protease activated receptor 2 (Par2) plays a pivotal role in various damage models, influencing injury, proliferation, inflammation, and regeneration. Despite extensive studies, its binary roles- EITHER aggravating injury or promoting recovery-make a conclusive translational decision on its modulation strategy elusive. Analyzing two liver regeneration models, autoimmune hepatitis and direct hepatic damage, we discovered Par2's outcome depends on the injury's nature. In immune-mediated injury, Par2 exacerbates damage, while in direct tissue injury, it promotes regeneration. Subsequently, we evaluated the clinical significance of this finding by investigating Par2's expression in the context of autoimmune diabetes. We found that the absence of Par2 in all lymphocytes provided full protection against the autoimmune destruction of insulin-producing β-cells in mice, whereas the introduction of a β-cell-specific Par2 null mutation accelerated the onset of autoimmune diabetes. This pattern led us to hypothesize whether these observations are universal. A comprehensive review of recent Par2 publications across tissues and systems confirms the claim drafted above: Par2's initial activation in the immune system aggravates inflammation, hindering recovery, whereas its primary activation in the damaged tissue fosters regeneration. As a membrane-anchored receptor, Par2 emerges as an attractive drug target. Our findings highlight a crucial translational modulation strategy in regenerative medicine based on injury type.

Cyclophilin Inhibition Protects Against Experimental Acute Kidney Injury and Renal Interstitial Fibrosis

Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease.

Activation of protease-activated receptor 2 is associated with blood pressure regulation and proteinuria reduction in metabolic syndrome

Metabolic syndrome (MetS) increases the risk of kidney disease. In SHRSP.Z-Lepr^fa /IzmDmcr (SHRSP.ZF) rats with MetS, protease-activated receptor 2 (PAR2)-mediated vasorelaxation is preserved in the aorta at 20 weeks of age (weeks) via enhancement of nitric oxide production but impaired at 30 weeks by oxidative stress. However, impairment of PAR2-mediated vasorelaxation of renal arteries and its possible implications for kidney disease are unclear. We used organ baths to assess PAR2-mediated vasorelaxation of isolated renal arteries, colorimetric methods to measure urinary protein levels as an index of renal function, and western blot to determine expression of PAR2 and nephrin proteins in the kidneys of SHRSP.ZF rats at 10, 20, and 30 weeks. We assessed renal arteries and kidney function for effects of orally administered GB88, a pathway-dependent PAR2 antagonist, from 10 to 18 weeks, and azilsartan, an angiotensin II type 1 receptor blocker, from 13 to 23 weeks. PAR2-mediated vasorelaxation was slightly lower at 20 weeks and attenuated significantly at 30 weeks compared with those at 10 weeks. Urinary protein levels were increased at 20 and 30 weeks. Decreased protein expression of PAR2 and nephrin in the kidney were observed at 30 weeks. Administration of GB88 increased blood pressure (BP) and proteinuria. Azilsartan reduced the high BP and the impaired PAR2-mediated vasorelaxation, but did not restore the increase in urinary protein levels and decreased PAR2 and nephrin protein expression in the kidney. PAR2 activation in the kidney may be associated with maintenance of BP and urinary protein excretion in MetS.

High-Dose Dexamethasone Manipulates the Tumor Microenvironment and Internal Metabolic Pathways in Anti-Tumor Progression

High-dose dexamethasone (DEX) is used to treat chemotherapy-induced nausea and vomiting or to control immunotherapy-related autoimmune diseases in clinical practice. However, the underlying mechanisms of high-dose DEX in tumor progression remain unaddressed. Therefore, we explored the effects of high-dose DEX on tumor progression and the potential mechanisms of its anti-tumor function using immunohistochemistry, histological examination, real-time quantitative PCR (qPCR), and Western blotting. Tumor volume, blood vessel invasion, and levels of the cell proliferation markers Ki67 and c-Myc and the anti-apoptotic marker Bcl2 decreased in response to high-dose DEX. However, the cell apoptosis marker cleaved caspase 3 increased significantly in mice treated with 50 mg/kg DEX compared with controls. Some genes associated with immune responses were significantly downregulated following treatment with 50 mg/kg DEX e.g., Cxcl9, Cxcl10, Cd3e, Gzmb, Ifng, Foxp3, S100a9, Arg1, and Mrc1. In contrast, the M1-like tumor-associated macrophages (TAMs) activation marker Nos2 was shown to be increased. Moreover, the expression of peroxisome proliferator-activated receptors α and γ (Pparα and Pparg, respectively) was shown to be significantly upregulated in livers or tumors treated with DEX. However, high-dose DEX treatment decreased the expression of glucose and lipid metabolic pathway-related genes such as glycolysis-associated genes (Glut1, Hk2, Pgk1, Idh3a), triglyceride (TG) synthesis genes (Gpam, Agpat2, Dgat1), exogenous free fatty acid (FFA) uptake-related genes (Fabp1, Slc27a4, and CD36), and fatty acid oxidation (FAO) genes (Acadm, Acaa1, Cpt1a, Pnpla2). In addition, increased serum glucose and decreased serum TG and non-esterified fatty acid (NEFA) were observed in DEX treated-xenografted tumor mice. These findings indicate that high-dose DEX-inhibited tumor progression is a complicated process, not only activated by M1-like TAMs, but also decreased by the uptake and consumption of glucose and lipids that block the raw material and energy supply of cancer cells. Activated M1-like TAMs and inefficient glucose and lipid metabolism delayed tumor cell growth and promoted apoptosis. These findings have important implications for the application of DEX combined with drugs that target key metabolism pathways for tumor therapy in clinical practice.