calpastatin and Kidney-Diseases

The nicotinic acetylcholine receptor α1 (nAChRα1) was investigated as a potential proinflammatory molecule in the kidney, given a recent report that it is an alternative urokinase plasminogen activator (uPA) receptor, in addition to the classical receptor uPAR. Two animal models and in vitro monocyte studies were involved: (1) In an ApoE(-/-) mouse model of chronic kidney disease, glomerular-resident cells and monocytes/macrophages were identified as the primary cell types that express nAChRα1 during hypercholesterolemia/uninephrectomy-induced nephropathy. Silencing of the nAChRα1 gene for 4 months (6 months on Western diet) prevented the increases in renal monocyte chemoattractant protein-1 and osteopontin expression levels and F4/80+ macrophage infiltration compared with the nonsilenced mice. These changes were associated with significantly reduced transforming growth factor-β1 mRNA (50% decrease) and α smooth muscle actin-positive (αSMA+) myofibroblasts (90% decrease), better glomerular and tubular basement membranes (GBM/TBM) preservation (threefold less disintegration), and better renal function preservation (serum creatinine 40% lower) in the nAChRα1-silenced mice. The nAChRα1 silencing was also associated with significantly reduced renal tissue calcium deposition (78% decrease) and calpain-1 (but not calpain-2) activation (70% decrease). (2) The nAChRα1 was expressed in vitro by mouse monocyte cell line WEHI-274.1. The silencing of nAChRα1 significantly reduced both calpain-1 and -2 activities, and reduced the degradation of the calpain substrate talin. (3) To further explore the role of calpain-1 activity in hypercholesterolemic nephropathy, disease severities were compared in CAST(-/-)ApoE(-/-) (calpain overactive) mice and ApoE(-/-) mice fed with Western diet for 10 months (n=12). Macrophages were the main cell type of renal calpain-1 production in the model. The number of renal F4/80+ macrophages was 10-fold higher in the CAST(-/-)ApoE(-/-) mice (P<0.05), and was associated with a significantly higher level of αSMA+ cells, increased GBM/TBM destruction, and higher serum creatinine levels. Our studies suggest that the receptor nAChRα1 is an important regulator of calpain-1 activation and inflammation in the chronic hypercholesterolemic nephropathy. This new proinflammatory pathway may also be relevant to other disorders beyond hyperlipidemic nephropathy.

Topics: Actins; Animals; Antigens, Differentiation; Apolipoproteins E; Blotting, Northern; Blotting, Western; Calcium-Binding Proteins; Calpain; Cell Line; Female; Hypercholesterolemia; Inflammation; Kidney; Kidney Diseases; Macrophages; Male; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Monocytes; Nephrectomy; Receptors, Nicotinic; RNA Interference; Transforming Growth Factor beta1

Calcium homeostasis is disturbed in many ways in the course of chronic kidney disease (CKD). The concentration of free cytoplasmic calcium in erythrocytes is increased. Maintenance of a high concentration gradient (between the cystoplasmic and extracellular space) is possible only due to a finely tuned cooperation between many regulating systems in the cytoplasmic membranes and cell organelles. The aim of our study was to evaluate the activity of Ca(2+)-Mg(2+)-dependent ATPase (PMCA), calmodulin and calpain-calpastatin (CANP-CAST) system in erythrocytes of CKD children treated conservatively in the stages II-IV.. A total of 36 patients with CKD were enrolled in the study. Group A contained patients with CKD stage II; group B with CKD stage III; and group C with CKD stage IV. The control group D consisted of 30 healthy subjects. In the serum, we determined the following: intact parathormon, total calcium, creatinine; in the red blood cells: free cytosolic calcium concentration (Ca(i)(2+)), activity of Ca(2+)-Mg(2+)-transporting ATPase (PMCA), basal PMCA (bPMCA), calmodulin (CALM), CANP, CAST.. In all groups, Ca(i)(2+) concentrations were significantly higher, whereas PMCA and bPMCA activity were lower than in the controls. CANP concentrations in group A were elevated compared to the controls, whereas in groups B and C they were significantly lower. In group C, the mean CAST activity reached the highest values. CALM concentrations were decreased versus controls in all groups of patients.. The intracellular Ca(i)(2+) homeostasis is disturbed in children with CKD and aggravates the deterioration of renal function as well. The reasons for the progressing increase of erythrocyte calcium concentration are multifactorial. Undoubtedly, the decreased PMCA activity, the calmodulin deficiency and the dysregulated CANP-CAST system are responsible for that phenomenon. The impact of many other biological modulators, creating a network defending the cell against the calcium accumulation, cannot be excluded.

Topics: Adolescent; Ca(2+) Mg(2+)-ATPase; Calcium-Binding Proteins; Calmodulin; Calpain; Child; Chronic Disease; Erythrocytes; Humans; Kidney Diseases

Calpains are a family of 14 intracellular calcium-dependent proteases, which have been implicated in cardiovascular diseases. We aimed to analyze specifically the expressional regulation of the different calpain isoforms in hypertensive target organ damage. Using real-time PCR, we found calpain 6 and 9 down-regulated by more than 50% and the endogenous calpain inhibitor calpastatin up-regulated by 225%, respectively, in the hearts of Dahl salt-sensitive rats on a high salt (4% NaCl) compared to normal salt diet. On the protein level, calpain 9 but not calpastatin was regulated in the hypertensive target organs heart and kidney. Moreover, the myocardial expression of calpain 9 protein was inversely linked to left ventricular mass (r= -0.93, p<0.01), and renal expression of calpain 9 protein correlated inversely with albuminuria (r= -0.82, p<0.05). In the aorta, there was no regulation of calpain 9 on the protein level. We conclude that differential regulation of calpain 9 may play a role in hypertensive target organ damage.

Topics: Animals; Calcium-Binding Proteins; Calpain; Down-Regulation; Gene Expression Regulation, Enzymologic; Heart Diseases; Heart Ventricles; Hypertension; Isoenzymes; Kidney Diseases; Male; Rats; Rats, Inbred Dahl; RNA, Messenger