背景:肾素依赖性高血压伴肾小管间质损伤仍然是临床上患病率高的问题。然而,肾素是否以及如何参与肾小管间质损伤仍不完全清楚。新的证据表明肾素将C3切割成C3a和C3b。在本研究中,我们旨在探讨肾素介导的C3a/C3a受体(C3aR)信号在肾素依赖性高血压诱导的肾损伤中的作用,并阐明其详细机制.
方法:用ELISA法检测与重组肾素孵育的健康志愿者血清中C3a浓度的变化。在恶性小动脉肾硬化和良性小动脉肾硬化患者的肾活检切片中评估了人肾小管上皮细胞中的C3aR表达。人肾2(HK2)细胞经人血清处理后,检测到C3aR变化,Renin和Aliskiren.C3a类似物和C3aR拮抗剂SB290157用于刺激HK2细胞以探索C3a/C3aR活化的下游信号传导。对于体内研究,两个肾,建立单夹(2K1C)高血压大鼠模型,以模拟肾素依赖性高血压条件。在修剪的肾脏中检测到C3a和C3aR表达。腹膜内注射SB290157以阻断2K1C大鼠的C3a/C3aR信号传导。
结果:结果表明,肾素将人和大鼠的肾小管上皮细胞(TECs)中的C3裂解为C3a,并激活了C3a/C3aR信号传导。体外结果表明,C3a/C3aR激活损害了HK2细胞中过氧化物酶体增殖物激活受体α(PPARα)/肉碱棕榈酰转移酶-1α(CPT-1α)介导的线粒体脂肪酸氧化(MitoFAO),并诱导HK2细胞转变为促纤维化表型,通过用C3aR拮抗剂SB290157治疗而被抑制。体内结果表明,肾素mRNA水平,C3a浓度,在2K1C大鼠的肾皮质中,C3aR水平和肾小管间质纤维化同时增加。用C3aR拮抗剂SB290157治疗可显着减轻肾素诱导C3aR表达的作用,并通过改善TECs中PPARα/CPT-1α介导的MitoFAO减轻肾素依赖性高血压诱导的肾小管间质纤维化,以及抑制肾小管纤维化表型转变。
结论:我们的结果证明肾素通过损害PPARα/CPT-1α介导的肾小管米托FAO激活C3a/C3aR信号促进肾小管间质纤维化。SB290157为肾素依赖性高血压引起的肾损伤提供了潜在的治疗方法。
Renin-dependent hypertension with tubulointerstitial injury remains a problem with high prevalence in the clinic. However, whether and how renin participates in tubulointerstitial injury remains incompletely understood. New evidence suggests that renin cleaves C3 into C3a and C3b. In the present study, we aimed to explore the role of renin-mediated C3a/C3a receptor (C3aR) signaling in renin-dependent hypertension-induced kidney injury and illustrate the detailed mechanisms.
C3a concentration changes in serum from healthy volunteers incubated with recombinant renin were detected by ELISA. C3aR expression in human tubular epithelial cells was evaluated in renal biopsy sections from malignant arteriolonephrosclerosis and benign arteriolonephrosclerosis patients. C3aR changes in human kidney 2 (HK2) cells were detected after the cells were treated with human serum, renin and aliskiren. The C3a analogue and C3aR antagonist SB290157 were used to stimulate HK2 cells to explore the downstream signaling of C3a/C3aR activation. For in vivo studies, two-kidney, one-clipped (2K1C) hypertensive rat model was established to simulate renin-dependent hypertension conditions. C3a and C3aR expression was detected in the clipped kidneys. SB290157 was injected intraperitoneally to block C3a/C3aR signaling in 2K1C rats.
The results showed that renin cleaved C3 into C3a and activated C3a/C3aR signaling in tubular epithelial cells (TECs) from both humans and rats. In vitro results demonstrated that C3a/C3aR activation impaired peroxisome proliferator-activated receptor alpha (PPARα)/carnitine palmitoyltransterase-1alpha (CPT-1α)-mediated mitochondrial fatty acid oxidation (Mito FAO) in HK2 cells and induced HK2 cell transition to a profibrotic phenotype, which was inhibited by treatment with the C3aR antagonist SB290157. In vivo results showed that renin mRNA levels, C3a concentrations, C3aR levels and tubulointerstitial fibrosis increased concurrently in the clipped kidney cortex of 2K1C rats. Treatment with the C3aR antagonist SB290157 significantly mitigated the effect of renin induction of C3aR expression and alleviated renin-dependent hypertension-induced tubulointerstitial fibrosis by improving PPARα/CPT-1α-mediated Mito FAO in TECs, as well as inhibiting tubular profibrotic phenotype transition.
Our results prove that renin activates C3a/C3aR signaling to promote renal tubulointerstitial fibrosis by impairing PPARα/CPT-1α-mediated tubular Mito FAO. SB290157 confers a potential therapeutic approach for renin-dependent hypertension-induced kidney injury.