Distinct roles of arginases 1 and 2 in diabetic nephropathy

Sidney M. Morris, Hanning You, Ting Gao, Jean Vacher, Timothy K. Cooper, Alaa S. Awad
2017 AJP - Renal Physiology  
Morris SM Jr, You H, Gao T, Vacher J, Cooper TK, Awad AS. Distinct roles of arginases 1 and 2 in diabetic nephropathy. Diabetes is the leading cause of end-stage renal disease, resulting in a significant health care burden and loss of economic productivity by affected individuals. Because current therapies for progression of diabetic nephropathy (DN) are only moderately successful, identification of underlying mechanisms of disease is essential to develop more effective therapies. We showed
more » ... pies. We showed previously that inhibition of arginase using S-(2boronoethyl)-L-cysteine (BEC) or genetic deficiency of the arginase-2 isozyme was protective against key features of nephropathy in diabetic mouse models. However, those studies did not determine whether all markers of DN were dependent only on arginase-2 expression. The objective of this study was to identify features of DN that are associated specifically with expression of arginase-1 or Ϫ2. Elevated urinary albumin excretion rate and plasma urea levels, increases in renal fibronectin mRNA levels, and decreased renal medullary blood flow were associated almost completely and specifically with arginase-2 expression, indicating that arginase-2 selectively mediates major aspects of diabetic renal injury. However, increases in renal macrophage infiltration and renal TNF-␣ mRNA levels occurred independent of arginase-2 expression but were almost entirely abolished by treatment with BEC, indicating a distinct role for arginase-1. We therefore generated mice with a macrophage-specific deletion of arginase-1 (CD11b Cre /Arg1 fl/fl ). CD11b Cre /Arg1 fl/fl mice had significantly reduced macrophage infiltration but had no effect on albuminuria compared with Arg1 fl/fl mice after 12 wk of streptozotocin-induced diabetes. These results indicate that selective inhibition of arginase-2 would be effective in preventing or ameliorating major features of diabetic renal injury. arginase; macrophages DIABETES MELLITUS IS the most common cause of kidney failure, accounting for Ͼ40% of new cases each year (2). Early features in diabetic nephropathy (DN) include development of glomerular hyperfiltration and hypertrophy, followed by thickening of the glomerular basement membrane, endothelial cell dysfunction, albuminuria (1, 15), and ultimately progression to glomerular sclerosis and end-stage renal failure (1). Unfortunately, therapies to control blood glucose and blood pressure, along with lifestyle changes, are only moderately effective in delaying the progression of DN. Thus, further elucidation of the mechanisms underlying the development and progression of renal damage is essential for developing more effective therapies. We showed previously that arginase inhibition can prevent or greatly reduce several major features of DN in several mouse models (14) and that arginase inhibition confers renal protection via an eNOS-dependent mechanism (21). Arginase catalyzes hydrolysis of L-arginine to L-ornithine and urea and thus can compete with NOS for the common substrate L-arginine (19). Our previous results obtained with the arginase inhibitor S-(2-boronoethyl)-L-cysteine (BEC) were limited by the facts that mammals express two distinct arginase isozymes (arginases-1 and -2) encoded by different genes (11) and that no commercially available arginase inhibitors are specific for either individual arginase isozyme. Normal kidney expresses arginase-2, with no detectable expression of arginase-1 (14). Using a mouse strain lacking arginase-2 (Arg2 Ϫ/Ϫ ), we found that several, but not all, key markers of DN that were prevented or reduced by arginase inhibition were mediated via arginase-2 (14). Our previous report demonstrated that several features of DN were ameliorated or abolished in Arg2 Ϫ/Ϫ mice (14) but did not determine whether arginase-2 deficiency was sufficient to prevent or reduce all indicators of renal damage. Therefore, the current study was performed to determine whether any markers of DN were independent of arginase-2. We show that arginase-2-independent aspects of DN were dependent on arginase-1 expression. Whereas arginase-2 expression directly and specifically mediates increased urinary albumin excretion rate, increased plasma urea levels, and decreased renal medullary blood flow in diabetes, increases in renal macrophage infiltration and renal TNF-␣ mRNA levels are dependent on arginase-1 expression in macrophages. These results support the notion that isozyme-selective inhibition of arginase may be a novel therapeutic intervention in the treatment of specific features of DN. MATERIALS AND METHODS Diabetic mouse models. Experiments were conducted in 6-wk-old male arginase-2-deficient (Arg2 Ϫ/Ϫ ) mice (17) (kindly provided by Dr. Brendan Lee, Baylor College of Medicine) and their wild-type littermates. Mice with deletion of arginase-1 in myeloid cells were created by mating CD11b Cre mice (9) with Arg1 fl/fl mice (stock no. 008817; The Jackson Laboratory, Bar Harbor, ME). The offspring were genotyped and backcrossed with Arg1 fl/fl mice to obtain CD11b Cre /Arg1 fl/fl . Arg1 fl/fl mice lacking CD11b Cre were used as controls. All mice were provided TEKLAD irradiated global 10% protein rodent diet (catalog no.
doi:10.1152/ajprenal.00158.2017 pmid:28446459 fatcat:72ibahvlqvh5pk37sa5zajfkre