kn-93 and Necrosis

BACKGROUND The aim of this study was to explore the potential role of TRPC6 in the pathophysiology of HK-2 cell injury following ischemia reperfusion (I/R). MATERIAL AND METHODS TRPC6 expression was analyzed by immunofluorescence staining. siRNA was transfected to knockout of TRPC6 in HK-2 cells, and in vitro I/R was then induced. Cell apoptosis and necrosis were determined by Annexin V-FITC/PI staining. Necroptosis was determined by necrostatin-1 and expressions of necroptosis-related proteins were evaluated. OAG, SKF96365, or KN-93 was further used to interfere with TRPC6 expression. RESULTS Cytoplasmic TRPC6 expression was demonstrated. I/R induced TRPC6 expression in normal or NC siRNA-transfected cells but not in TRPC6 siRNA-knockout ones. There was a progressive increase in apoptotic and necrotic cells with increasing reoxygenation time in all 3 groups, while necrosis in TRPC6 siRNA-transfected cells was comparatively higher than that of the other 2 groups (p<0.05). Expressions of necroptosis-related proteins were interfered with following I/R and these effects were enhanced by TRPC6 siRNA. Application of OAG, SKF96365, or KN93 further affected necroptosis following I/R. CONCLUSIONS This study described the expression and functional relevance of TRPC6 in the pathophysiology of HK-2 cell following I/R. Our results regarding the ability of TRPC6 to specifically interrupt necroptosis may shed new light on its role in prevention and control of ischemic kidney injury.

Topics: Apoptosis; Benzylamines; Blotting, Western; Cell Line; Cell Shape; Down-Regulation; Epithelial Cells; Fluorescent Antibody Technique; Humans; Imidazoles; Ischemia; Kidney Tubules; Necrosis; Oxygen; Protective Agents; Reperfusion Injury; RNA, Small Interfering; Sulfonamides; TRPC Cation Channels; TRPC6 Cation Channel; Up-Regulation

While Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been suggested to be an important protein regulating heart function upon ischemia/reperfusion (I/R), the mechanisms responsible are not fully known. Furthermore, it is not known whether CaMKII activation can modulate necroptosis, a recently described form of programmed cell death. In order to investigate these issues, Langendroff-perfused rat hearts were subjected to global ischemia and reperfusion, and CaMKII inhibition was achieved by adding the CaMKII inhibitor KN-93 (0.5 μmol/dm(3)) to the perfusion solution before the induction of ischemia. Immunoblotting was used to detect changes in expression of proteins modulating both necroptotic and apoptotic cell death. CaMKII inhibition normalized I/R induced increases in expression of necroptotic RIP1 and caspase-8 along with proteins of the intrinsic apoptotic pathway, namely cytochrome c and caspase-9. In addition, it increased the Bcl-2/Bax ratio and reduced caspase-3 and cleaved PARP1 content suggesting reduction of cell death. These changes coexisted with improvement of postischemic contractile function. On the other hand, there was no correlation between levels of pT287-CaMKIIδ and LVDP recovery after I/R. These results demonstrate for the first time that CaMKII inhibition may mitigate cardiac contractile dysfunction, at least partially, by limiting the contents of not only apoptotic, but also necroptotic proteins. Phosphorylation of CaMKII seems unlikely to determine the degree of postischemic recovery of contractile function.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Caspase 3; Caspase 8; Caspase 9; Cytochromes c; Heart Ventricles; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Necrosis; Nuclear Pore Complex Proteins; Phosphorylation; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; RNA-Binding Proteins; Sulfonamides

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the regulation of cardiac excitation-contraction coupling (ECC) as well as in apoptotic signaling and adverse remodeling. The goal of the present study is to investigate the role of CaMKII in irreversible ischemia and reperfusion (I/R) injury.. Isovolumic Langendorff perfused rat hearts were subjected to global no-flow I/R (45 min/120 min), and isolated myocytes were subjected to a protocol of simulated I/R (45 min simulated ischemia/60 min reoxygenation) either in the absence or presence of CaMKII inhibition [KN-93 (KN) or the CaMKII inhibitory peptide (AIP)].. In I/R hearts, an increase in CaMKII activity at the beginning of reperfusion was confirmed by the significantly increased phosphorylation of the Thr(17) site of phospholamban. In the presence of KN, contractile recovery at the end of reperfusion was almost double that of I/R hearts. This recovery was associated with a significant decrease in the extent of infarction, lactate dehydrogenase release (necrosis), TUNEL-positive cells, caspase-3 activity, and an increase in the Bcl-2/Bax ratio (apoptosis). In isolated myocytes, both KN and AIP prevented simulated I/R-induced spontaneous contractile activity and cell mortality. Similar results were obtained when inhibiting the reverse mode Na(+)/Ca(2+) exchanger (NCX) with KB-R7943, sarcoplasmic reticulum (SR) function with ryanodine and thapsigargin, or SR Ca(2+) release with tetracaine. In contrast, overexpression of CaMKII decreased cell viability from 52+/-3% to 26+/-2%.. Taken together, the present findings are the first to establish CaMKII as a fundamental component of a cascade of events integrating the NCX, the SR, and mitochondria that promote cellular apoptosis and necrosis in irreversible I/R injury.

Topics: Animals; Apoptosis; Benzylamines; Calcium; Calcium-Binding Proteins; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Cells, Cultured; L-Lactate Dehydrogenase; Male; Myocardial Reperfusion Injury; Myocardium; Myocytes, Cardiac; Necrosis; Perfusion; Phosphorylation; Rats; Sarcoplasmic Reticulum; Sodium-Calcium Exchanger; Sulfonamides; Thiourea; Time Factors