Genetic and pharmacological inhibition of GRPR protects against acute kidney injury via attenuating renal inflammation and necroptosis

RG108 attenuates acute kidney injury by inhibiting P38 MAPK/FOS and JNK/JUN pathways

Acute kidney injury (AKI) is an important clinical syndrome characterised by a sudden decline in renal function, often accompanied by renal inflammation and tubular epithelial cell damage. It has been reported that inhibiting DNA methylation significantly suppress the progression of AKI. In the current study, we investigate the effect of the DNA methyltransferase (DNMT) inhibitor RG108 in cisplatin- and hypoxia-reoxygenation-induced AKI. The expression of kidney injury molecules and inflammatory factors was examined by immunofluorescence, Western blotting and Real-time PCR. The results demonstrated that RG108 treatment significantly reduced kidney inflammation and injury. Furthermore, RNA-seq analysis was performed to reveal the regulatory mechanism of RG108 in AKI. The expression of the FOS and JUN genes, which are downstream of the MAPK pathway, were significant increased in AKI. Meanwhile, the expression of FOS and JUN were both inhibited by RG108, which is similar to what we found treatment with a specific JNK inhibitor and a specific p38 MAPK inhibitor, and thus attenuated renal inflammation and injury. In conclusion, we suggest that RG108 inhibits P38 MAPK/FOS and JNK/JUN pathways and attenuates renal injury and inflammatory responses. In these results, RG108 may become a novel MAPK pathway inhibitor and a clinical candidate for the treatment of AKI.

Gastrin-releasing peptide receptor antagonist RC-3095 inhibits Porphyromonas gingivalis lipopolysaccharide-accelerated atherosclerosis by suppressing inflammatory responses in endothelial cells and macrophages

OBJECTIVE

Porphyromonas gingivalis (P. gingivalis), one of the major periodontopathogens, is associated with the progression and exacerbation of atherosclerosis. In this study, we aimed to investigate whether the gastrin-releasing peptide receptor antagonist, RC-3095, could attenuate P. gingivalis LPS-induced inflammatory responses in endothelial cells and macrophages, as well as atherosclerosis in an ApoE-/- mouse model treated with P. gingivalis LPS.

METHODS

The effect of RC-3095 on P. gingivalis LPS-induced endothelial inflammation was examined using HUVECs and rat aortic endothelium. THP-1 cells were polarized into M1 macrophages by exposure to P. gingivalis LPS, with or without RC-3095. The effect of RC-3095 on atherosclerosis progression was assessed in high-fat-fed male ApoE-/- mice through injections of P. gingivalis LPS, RC-3095, or a combination of both.

RESULTS

RC-3095 significantly reduced P. gingivalis LPS-induced leukocyte adhesion to endothelial cells and aortic endothelium by suppressing NF-κB-dependent expressions of ICAM-1 and VCAM-1. In addition, RC-3095 inhibited the P. gingivalis LPS-induced polarization of M1 macrophages by blocking the MAPK and NF-κB signaling pathways. Moreover, RC-3095 decreased the area of atherosclerotic lesions in ApoE-/- mice, which was accelerated by P. gingivalis LPS injection, and lowered the expressions of ICAM-1 and VCAM-1 in the aortic tissue of mice with atherosclerosis.

CONCLUSIONS

RC-3095 can alleviate P. gingivalis LPS-induced endothelial inflammation, macrophage polarization, and atherosclerosis progression, suggesting its potential as a therapeutic approach for periodontal pathogen-associated atherosclerosis.

Aurantiamide mitigates acute kidney injury by suppressing renal necroptosis and inflammation via GRPR-dependent mechanism

Acute kidney injury (AKI) manifests as a clinical syndrome characterised by the rapid accumulation of metabolic wastes, such as blood creatinine and urea nitrogen, leading to a sudden decline in renal function. Currently, there is a lack of specific therapeutic drugs for AKI. Previously, we identified gastrin-releasing peptide receptor (GRPR) as a pathogenic factor in AKI. In this study, we investigated the therapeutic potential of a novel Chinese medicine monomer, aurantiamide (AA), which exhibits structural similarities to our previously reported GRPR antagonist, RH-1402. We compared the therapeutic efficacy of AA with RH-1402 both in vitro and in vivo using various AKI models. Our results demonstrated that, in vitro, AA attenuated injury, necroptosis, and inflammatory responses in human renal tubular epithelial cells subjected to repeated hypoxia/reoxygenation and lipopolysaccharide stimulation. In vivo, AA ameliorated renal tubular injury and inflammation in mouse models of ischemia/reperfusion and cecum ligation puncture-induced AKI, surpassing the efficacy of RH-1402. Furthermore, molecular docking and cellular thermal shift assay confirmed GRPR as a direct target of AA, which was further validated in primary cells. Notably, in GRPR-silenced HK-2 cells and GRPR systemic knockout mice, AA failed to mitigate renal inflammation and injury, underscoring the importance of GRPR in AA's mechanism of action. In conclusion, our study has demonstrated that AA serve as a novel antagonist of GRPR and a promising clinical candidate for AKI treatment.

Regulated necrosis role in inflammation and repair in acute kidney injury

Acute kidney injury (AKI) frequently occurs in patients with chronic kidney disease (CKD) and in turn, may cause or accelerate CKD. Therapeutic options in AKI are limited and mostly relate to replacement of kidney function until the kidneys recover spontaneously. Furthermore, there is no treatment that prevents the AKI-to-CKD transition. Regulated necrosis has recently emerged as key player in kidney injury. Specifically, there is functional evidence for a role of necroptosis, ferroptosis or pyroptosis in AKI and the AKI-to-CKD progression. Regulated necrosis may be proinflammatory and immunogenic, triggering subsequent waves of regulated necrosis. In a paradigmatic murine nephrotoxic AKI model, a first wave of ferroptosis was followed by recruitment of inflammatory cytokines such as TWEAK that, in turn, triggered a secondary wave of necroptosis which led to persistent kidney injury and decreased kidney function. A correct understanding of the specific forms of regulated necrosis, their timing and intracellular molecular pathways may help design novel therapeutic strategies to prevent or treat AKI at different stages of the condition, thus improving patient survival and the AKI-to-CKD transition. We now review key regulated necrosis pathways and their role in AKI and the AKI-to-CKD transition both at the time of the initial insult and during the repair phase following AKI.