Renoprotective effects of the novel prostaglandin EP4 receptor-selective antagonist ASP7657 in 5/6 nephrectomized chronic kidney disease rats

Studies in Zebrafish and Rat Models Support Dual Blockade of EP2 and EP4 (Prostaglandin E2 Receptors Type 2 and 4) for Renoprotection in Glomerular Hyperfiltration and Albuminuria

BACKGROUND

Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. Upregulation of COX2 (cyclooxygenase 2) and prostaglandin E₂ (PGE₂) was linked to podocyte damage in GH. We explored the potential renoprotective effects of either separate or combined pharmacological blockade of EP2 (PGE₂ receptor type 2) and EP4 (PGE₂ receptor type 4) in GH.

METHODS

We conducted in vivo studies in a transgenic zebrafish model (Tg[fabp10a:gc-EGFP]) suitable for analysis of glomerular filtration barrier function and a genetic rat model with GH, albuminuria, and upregulation of PGE₂. Similar pharmacological interventions and primary outcome analysis on albuminuria phenotype development were conducted in both model systems.

RESULTS

Stimulation of zebrafish embryos with PGE₂ induced an albuminuria-like phenotype, thus mimicking the suggested PGE₂ effects on glomerular filtration barrier dysfunction. Both separate and combined blockade of EP2 and EP4 reduced albuminuria phenotypes in zebrafish and rat models. A significant correlation between albuminuria and podocyte damage in electron microscopy imaging was identified in the rat model. Dual blockade of both receptors showed a pronounced synergistic suppression of albuminuria. Importantly, this occurred without changes in arterial blood pressure, glomerular filtration rate, or tissue oxygenation in magnetic resonance imaging, while RNA sequencing analysis implicated a potential role of circadian clock genes.

CONCLUSIONS

Our findings confirm a role of PGE₂ in the development of albuminuria in GH and support the renoprotective potential of combined pharmacological blockade of EP2 and EP4 receptors. These data support further translational research to explore this therapeutic option and a possible role of circadian clock genes.

Blockade of prostaglandin E2 receptor 4 ameliorates peritoneal dialysis-associated peritoneal fibrosis

Inflammatory responses in the peritoneum contribute to peritoneal dialysis (PD)-associated peritoneal fibrosis. Results of our previous study showed that increased microsomal prostaglandin E synthase-1-mediated production of prostaglandin E2 (PGE2) contributed to peritoneal fibrosis. However, the role of its downstream receptor in the progression of peritoneal fibrosis has not been established. Here, we examined the role of PGE2 receptor 4 (EP4) in the development of peritoneal fibrosis. EP4 was significantly upregulated in peritoneal tissues of PD patients with ultrafiltration failure, along with the presence of an enhanced inflammatory response. In vitro experiments showed that exposure to high glucose concentrations enhanced EP4 expression in rat peritoneal mesothelial cells (RPMCs). High-glucose–induced expression of inflammatory cytokines (monocyte chemoattractant protein-1, tumour necrosis factor α, and interleukin 1β) was significantly reduced in RPMCs treated with ONO-AE3-208, an EP4 receptor antagonist. ONO-AE3-208 also significantly decreased the expression of extracellular matrix proteins induced by high glucose concentrations. Furthermore, ONO-AE3-208 blunted activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and phosphorylation of nuclear factor kappa B (NF-κB) (p-p65). To further investigate the functional role of EP4, ONO-AE3-208 was administrated for 4 weeks in a rat model of PD, the results of which showed that ONO-AE3-208 inhibited peritoneal fibrosis and improved peritoneal dysfunction. Additionally, inflammatory cytokines in the peritoneum of PD rats treated with ONO-AE3-208 were downregulated, in line with inhibition of the NLRP3 inflammasome and NF-κB phosphorylation. In conclusion, an EP4 antagonist reduced the development of peritoneal fibrosis, possibly by suppressing NLRP3 inflammasome- and p-p65–mediated inflammatory responses. Our findings suggest that an EP4 antagonist may be therapeutically beneficial for PD-associated peritoneal fibrosis.

Yishen Qingli Heluo Granule Ameliorates Renal Dysfunction in 5/6 Nephrectomized Rats by Targeting Gut Microbiota and Intestinal Barrier Integrity

Chronic kidney disease (CKD) is often accompanied with imbalanced gut microbiota and impaired intestinal barrier. Hence, efforts to ameliorate renal dysfunction by manipulating gut microbial ecosystem are underway. Yishen Qingli Heluo granule (YQHG) is a representative traditional Chinese medicine (TCM) prescription for clinical treatment of CKD. However, its underlying mechanism has not been well elucidated. This study aimed to explore effects of YQHG on renal dysfunction in 5/6 nephrectomized rats by targeting gut microbiota and intestinal barrier. Here, we found that YQHG provided significant renal protection in 5/6 nephrectomized rats by reducing renal fibrosis and inflammation, reestablishing bacterial communities, and improving intestinal barrier. Our analysis showed that YQHG altered the bacterial community of 5/6 nephrectomized rats. In particular, the prescription significantly increased the relative abundance of SCFA-producing bacteria (i.e., Lactobacillaceae, Lactobacillus and Lactobacillus_gasseri), which was contributed to the improved SCFA concentration (i.e., total SCFA, acetic acid, butyric acid) and intestinal barrier (i.e., the improved permeability and microbial translocation). More critically, microbiota-transfer study showed that the protective effect of YQHG was partly attributed to the mediation of the gut microbiota, especially the SCFA-producing bacteria. Our current findings propose a microbiota-targeted intervention and indicate that YQHG may become a novel promising treatment for CKD.

Yishen Qingli Heluo Granule in the Treatment of Chronic Kidney Disease: Network Pharmacology Analysis and Experimental Validation

Background

Chronic kidney disease (CKD) is considered a global public health problem with high morbidity and mortality. Yishen Qingli Heluo granule (YQHG) is representative traditional Chinese medicine (TCM) remedy for clinical treatment of CKD. This study aims to explore the mechanism of YQHG on CKD through network pharmacology and experimental validation.

Methods

Traditional Chinese Medicine Systems Pharmacology (TCMSP) database and wide-scale literature mining were applied to screen active compounds of YQHG. Multiple bioinformatic tools and online databases were applied by us to obtain relevant targets of YQHG and CKD. The intersection targets between YQHG and CKD were considered as candidate targets. The compound-target, herb-candidate target and protein–protein interaction networks were constructed and visualized for topological analyses. GO and KEGG enrichment analyses were conducted to determine the biological processes and signaling pathways. Molecular docking was used to verify the reliability of network pharmacology. Finally, pharmacological evaluation was performed to explore the mechanism of YQHG against CKD on a 5/6 nephrectomy model.

Results

Seventy-nine candidate targets, ten core biological processes and one key signaling pathway (p53) were screened. PTGS2 was identified as a key target based on H-CT network. The molecular docking showed that Quercetin, Kaempferol, Luteolin were three key compounds with the best binding activity. In addition, IL6 and Quercetin could form a stable complex with high binding affinity (−7.29 kcal/mol). In vivo experiment revealed that YQHG improved kidney function and fibrosis in 5/6 nephrectomized rats. Moreover, the decreased expression of PTGS2, IL6, and the increased expression of p53 were observed in kidney tissue. Notably, the gut microbiota of rats treated with YQHG was reshaped, which was characterized by a reduced ratio of Firmicutes/Bacteroidota.

Conclusion

Our results predicted and verified the potential targets of YQHG on CKD from a holistic perspective, and provided valuable direction for the further research of YQHG.

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Kidney in the net of acute and long-haul coronavirus disease 2019: a potential role for lipid mediators in causing renal injury and fibrosis

PURPOSE OF REVIEW

Severe COVID-19 disease is often complicated by acute kidney injury (AKI), which may transition to chronic kidney disease (CKD). Better understanding of underlying mechanisms is important in advancing therapeutic approaches.

RECENT FINDINGS

SARS-CoV-2-induced endothelial injury initiates platelet activation, platelet-neutrophil partnership and release of neutrophil extracellular traps. The resulting thromboinflammation causes ischemia-reperfusion (I/R) injury to end organs. Severe COVID-19 induces a lipid-mediator storm with massive increases in thromboxane A2 (TxA2) and PGD2, which promote thromboinflammation and apoptosis of renal tubular cells, respectively, and thereby enhance renal fibrosis. COVID-19-associated AKI improves rapidly in the majority. However, 15-30% have protracted renal injury, raising the specter of transition from AKI to CKD.

SUMMARY

In COVID-19, the lipid-mediator storm promotes thromboinflammation, ischemia-reperfusion injury and cytotoxicity. The thromboxane A2 and PGD2 signaling presents a therapeutic target with potential to mitigate AKI and transition to CKD. Ramatroban, the only dual antagonist of the thromboxane A2/TPr and PGD2/DPr2 signaling could potentially mitigate renal injury in acute and long-haul COVID. Urgent studies targeting the lipid-mediator storm are needed to potentially reduce the heavy burden of kidney disease emerging in the wake of the current pandemic.