Effect of all-trans retinoic acid treatment on prohibitin and renin-angiotensin-aldosterone system expression in hypoxia-induced renal tubular epithelial cell injury

Background and objective: All-trans retinoic acid (ATRA) exerts various effects on physiological processes such as cell growth, differentiation, apoptosis and inflammation. Prohibitins (PHB), including prohibitin 1 (PHB1) and prohibitin 2 (PHB2), are evolutionary conserved and pleiotropic proteins implicated in various cellular functions, including proliferation, tumor suppression, apoptosis, transcription, and mitochondrial protein folding. The renin-angiotensin-aldosterone system plays a pivotal role in the regulation of blood pressure and volume homeostasis. All these factors and systems have been implicated in renal interstitial fibrosis. Therefore, the objective of this study was to investigate the effect of ATRA treatment on the renin-angiotensin-aldosterone system and expression of prohibitins to further understand its role in the processes leading to renal interstitial fibrosis. Methods: The hypoxic and oxidative stress conditions in obstructive renal disease were simulated in a hypoxia/reoxygenation model with renal tubular epithelial cells (RTEC) as a model system. Subsequently, the effect of ATRA on mRNA and protein expression levels was determined and correlations were established between factors involved in the renin-angiotensin-aldosterone system, the prohibitins, cellular redox status, renal interstitial fibrosis and ATRA treatment. Results: Correlation analysis showed that both PHB1 and PHB2 protein levels were negatively correlated with angiotensin I, ACE1, angiotensin II, TGF-1, Col-IV, FN, ROS, and MDA (PHB1: r = -0.792, -0.834, -0.805, -0.795, -0.778, -0.798, -0.751, -0.682; PHB2: r = -0.872, -0.799, -0.838, -0.773, -0.769, -0.841, -0.794, -0.826; each p < 0.05), but positively correlated with ACE2, SOD, and GSH (PHB1: r = 0.796, 0.879, 0.824; PHB2: r = 0.785, 0.914, 0.849; each p < 0.05). ACE1 was positively correlated with angiotensin I, angiotensin II, TGF-1, Col-IV, FN, ROS, and MDA, and negatively correlated with ACE2, SOD, and GSH (each p < 0.05). ACE2 was negatively correlated with ACE1, angiotensin I, angiotensin II, TGF-1, Col-IV, FN, ROS, and MDA, and positively correlated with SOD and GSH (each p < 0.05). Conclusion: The results suggest that ATRA acts as a positive regulator of PHB1, PHB2 and ACE2, and as a negative regulator of ACE1, angiotensin I, and angiotensin II in a RTEC model system under hypoxia/reoxygenation conditions.