Role of endoplasmic reticulum stress in renal damage after myocardial infarction

Myocardial infarction (MI) is associated with renal alterations resulting in poor outcomes in patients with MI. Renal fibrosis is a potent predictor of progression in patients and is often accompanied by inflammation and oxidative stress; however, the mechanisms involved in these alterations are not well established. Endoplasmic reticulum (ER) plays a central role in protein processing and folding. An accumulation of unfolded proteins leads to ER dysfunction, termed ER stress. Since the kidney is the organ with highest protein synthesis fractional rate, we herein investigated the effects of MI on ER stress at renal level, as well as the possible role of ER stress on renal alterations after MI. Patients and MI male Wistar rats showed an increase in the kidney injury marker neutrophil gelatinase-associated lipocalin (NGAL) at circulating level or renal level respectively. Four weeks post-MI rats presented renal fibrosis, oxidative stress and inflammation accompanied by ER stress activation characterized by enhanced immunoglobin binding protein (BiP), protein disulfide-isomerase A6 (PDIA6) and activating transcription factor 6-alpha (ATF6 alpha) protein levels. In renal fibroblasts, palmitic acid (PA; 50-200 mu M) and angiotensin II (Ang II; 10(-8) to 10(-6)M) promoted extracellular matrix, superoxide anion production and inflammatory markers up-regulation. The presence of the ER stress inhibitor, 4-phenylbutyric acid (4-PBA; 4 mu M), was able to prevent all of these modifications in renal cells. Therefore, the data show that ER stress mediates the deleterious effects of PA and Ang II in renal cells and support the potential role of ER stress on renal alterations associated with MI.