Epoxyeicosatrienoic acid metabolites inhibit Kir4.1/Kir5.1 in the distal convoluted tubule

Hypoxia Induces Apoptosis of Microglia BV2 by Upregulating Kir2.1 to Activate Mitochondrial-Related Apoptotic Pathways

Aim

To explore the role of Kir2.1 in hypoxia-induced microglial apoptosis.

Methods

BV2 microglial cell lines were cultured and treated with ML133 hydrochloride, a Kir2.1 channel blocker, for 23 h and with 500 μmol/L of CoCl₂ for 8 h. Cells were divided into the control, CoCl₂ (hypoxia-induced model), and CoCl₂+ML133 (hypoxia-induced model established after ML133 pretreatment) groups. Cell activity was assessed using the CCK-8 technique. The membrane potential and Kir2.1 current of BV2 were evaluated with the whole-cell patch-clamp technique. The protein levels and mRNA levels of Kir2.1, apoptotic proteins Bax and caspase-3, and antiapoptotic protein Bcl-2 in BV2 cells were evaluated via immunofluorescence, Western blot analysis, and real-time quantitative reverse transcription. The apoptosis rate of BV2 cells was detected via flow cytometry.

Results

CCK-8 analysis showed that the cell activity of each group increased initially and then decreased. The 2 h intervention group had the highest cell activity, and that of the 8 h group was >90%. Hence, there was a significant difference in the results (P < 0.05). Western blot analysis revealed that the expression of cleaved caspase-3 significantly increased in the 8 h group compared with the 0 h group. Compared with the control group, the expression of Kir2.1 and mRNA in the CoCl₂ group increased. Thus, hypoxia could upregulate the expression of Kir2.1. The whole-cell patch-clamp results showed that the Kir2.1 channel current amplitude of the CoCl₂ group increased compared with that of the control group. Therefore, hypoxia could enhance Kir2.1 function. The apoptosis rate of the CoCl₂ group was significantly higher than that of the control group. Further, the ML133 group had a significantly lower apoptosis rate than the CoCl₂ group. The expression of apoptotic proteins Bax and cleaved caspase-3 increased in the CoCl₂ group, and that of the antiapoptotic protein Bcl-2 decreased. The expression of apoptotic proteins Bax and cleaved caspase-3 reduced in the CoCl₂+ML133 group, whereas that of the antiapoptotic protein Bcl-2 increased.

Conclusion

Hypoxia can induce microglia BV2 apoptosis accompanied by the upregulation of Kir2.1 and mRNA expression levels and an increase in the Kir2.1 current. Moreover, ML133 can inhibit hypoxia-induced BV2 cell apoptosis. Hence, Kir2.1 may be involved in the process of hypoxia-induced BV2 cell apoptosis.

Orally active epoxyeicosatrienoic acid analogs in hypertension and renal injury

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites synthesized by cytochrome P450 epoxygenases. Biological activities for EETs include vasodilation, decreasing inflammation, opposing apoptosis, and inhibiting renal sodium reabsorption. These actions are beneficial in lowering blood pressure and slowing kidney disease progression. Furthermore, evidence in human and experimental animal studies have found that decreased EET levels contribute to hypertension and kidney diseases. Consequently, EET mimics/analogs have been developed as a potential therapeutic for hypertension and acute and chronic kidney diseases. Their development has resulted in EET analogs that are orally active with favorable pharmacological profiles. Analogs for 8,9-EET, 11,12-EET, and 14,15-EET have been tested in several hypertension and kidney disease animal models. More recently, kidney targeted EET analogs have been synthesized and tested against drug-induced nephrotoxicity. Experimental evidence has demonstrated compelling therapeutic potential for EET analogs to oppose cardiovascular and kidney diseases. These EET analogs lower blood pressure, decrease kidney inflammation, improve vascular endothelial function, and decrease kidney fibrosis and apoptosis. Overall, these preclinical studies support the likelihood that EET analogs will advance to clinical trials for hypertension and associated comorbidities or acute and chronic kidney diseases.

Epoxy Fatty Acids: From Salt Regulation to Kidney and Cardiovascular Therapeutics: 2019 Lewis K. Dahl Memorial Lecture

Epoxyeicosatrienoic acids (EETs) are epoxy fatty acids that have biological actions that are essential for maintaining water and electrolyte homeostasis. An inability to increase EETs in response to a high-salt diet results in salt-sensitive hypertension. Vasodilation, inhibition of epithelial sodium channel, and inhibition of inflammation are the major EET actions that are beneficial to the heart, resistance arteries, and kidneys. Genetic and pharmacological means to elevate EETs demonstrated antihypertensive, anti-inflammatory, and organ protective actions. Therapeutic approaches to increase EETs were then developed for cardiovascular diseases. sEH (soluble epoxide hydrolase) inhibitors were developed and progressed to clinical trials for hypertension, diabetes mellitus, and other diseases. EET analogs were another therapeutic approach taken and these drugs are entering the early phases of clinical development. Even with the promise for these therapeutic approaches, there are still several challenges, unexplored areas, and opportunities for epoxy fatty acids.