Mechanisms of Synergistic Interactions of Diabetes and Hypertension in Chronic Kidney Disease: Role of Mitochondrial Dysfunction and ER Stress
CURRENT HYPERTENSION REPORTS
Authors: Wang, Zhen; do Carmo, Jussara M.; da Silva, Alexandre A.; Fu, Yiling; Hall, John E.
Purpose of Review To discuss the importance of synergistic interactions of diabetes mellitus (DM) and hypertension (HT) in causing chronic kidney disease and the potential molecular mechanisms involved. Recent Findings DM and HTare the two most important risk factors for chronic kidney disease (CKD) and development of end-stage renal disease (ESRD). The combination of HTandDMmay synergistically promote the progression of renal injury through mechanisms that have not been fully elucidated. Hyperglycemia and other metabolic changes in DM initiate endoplasmic reticulum (ER) stress and mitochondrial (MT) adaptation in different types of glomerular cells. These adaptations appear to make the cells more vulnerable to HT-induced mechanical stress. Excessive activation of mechanosensors, possibly via transient receptor potential cation channel subfamily C member 6 (TRPC6), may lead to impaired calcium (Ca2+) homeostasis and further exacerbate ER stress and MT dysfunction promoting cellular apoptosis and glomerular injury. Summary The synergistic effects of HT and DM to promote kidney injury may be mediated by increased intraglomerular pressure. Chronic activation of mechanotransduction signaling may amplify metabolic effects of DM causing cellular injury through a vicious cycle of impaired Ca2+ homeostasis, mitochondrial dysfunction, and ER stress.
TRPV2 Channels Contribute to Stretch-Activated Cation Currents and Myogenic Constriction in Retinal Arterioles
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
Authors: McGahon, Mary K.; Fernandez, Jose A.; Dash, Durga P.; McKee, Jon; Simpson, David A.; Zholos, Alex V.; McGeown, J. Graham; Curtis, Tim M.
PURPOSE. Activation of the transient receptor potential channels, TRPC6, TRPM4, and TRPP1 (PKD2), has been shown to contribute to the myogenic constriction of cerebral arteries. In the present study we sought to determine the potential role of various mechanosensitive TRP channels to myogenic signaling in arterioles of the rat retina. METHODS. Rat retinal arterioles were isolated for RT-PCR, Fura-2 Ca2+ microfluorimetry, patch-clamp electrophysiology, and pressure myography studies. In some experiments, confocal immunolabeling of wholemount preparations was used to examine the localization of specific mechanosensitive TRP channels in retinal vascular smooth muscle cells (VSMCs). RESULTS. Reverse transcription-polymerase chain reaction analysis demonstrated mRNA expression for TRPC1, M7, V1, V2, V4, and P1, but not TRPC6 or M4, in isolated retinal arterioles. Immunolabeling revealed plasma membrane, cytosolic and nuclear expression of TRPC1, M7, V1, V2, V4, and P1 in retinal VSMCs. Hypoosmotic stretch-induced Ca2+ influx in retinal VSMCs was reversed by the TRPV2 inhibitor tranilast and the nonselective TRPP1/V2 antagonist amiloride. Inhibitors of TRPC1, M7, V1, and V4 had no effect. Hypoosmotic stretch-activated cation currents were similar in Na+ and Cs+ containing solutions suggesting no contribution by TRPP1 channels. Direct plasma membrane stretch triggered cation current activity that was blocked by tranilast and specific TRPV2 pore-blocking antibodies and mimicked by the TRPV2 activator, Delta 9-tetrahydrocannabinol. Preincubation of retinal arterioles with TRPV2 blocking antibodies prevented the development of myogenic tone. CONCLUSIONS. Our results suggest that retinal VSMCs express a range of mechanosensitive TRP channels, but only TRPV2 appears to contribute to myogenic signaling in this vascular bed.