Arginase-2 Mediates Diabetic Renal Injury

Abstract

OBJECTIVETo determine 1) whether renal arginase activity or expression is increased in diabetes and 2) whether arginase plays a role in development of diabetic nephropathy (DN).RESEARCH DESIGN AND METHODSThe impact of arginase activity and expression on renal damage was evaluated in spontaneously diabetic Ins2Akita mice and in streptozotocin (STZ)-induced diabetic Dilute Brown Agouti (DBA) and arginase-2–deficient mice (Arg2−/−).RESULTSPharmacological blockade or genetic deficiency of arginase-2 conferred kidney protection in Ins2Akita mice or STZ-induced diabetic renal injury. Blocking arginases using S-(2-boronoethyl)-l-cysteine for 9 weeks in Ins2Akita mice or 6 weeks in STZ-induced diabetic DBA mice significantly attenuated albuminuria, the increase in blood urea nitrogen, histopathological changes, and kidney macrophage recruitment compared with vehicle-treated Ins2Akita mice. Furthermore, kidney arginase-2 expression increased in Ins2Akita mice compared with control. In contrast, arginase-1 expression was undetectable in kidneys under normal or diabetes conditions. Arg2−/− mice mimicked arginase blockade by reducing albuminuria after 6 and 18 weeks of STZ-induced diabetes. In wild-type mice, kidney arginase activity increased significantly after 6 and 18 weeks of STZ-induced diabetes but remained very low in STZ-diabetic Arg2−/− mice. The increase in kidney arginase activity was associated with a reduction in renal medullary blood flow in wild-type mice after 6 weeks of STZ-induced diabetes, an effect significantly attenuated in diabetic Arg2−/− mice.CONCLUSIONSThese findings indicate that arginase-2 plays a major role in induction of diabetic renal injury and that blocking arginase-2 activity or expression could be a novel therapeutic approach for treatment of DN.

Protective role of small pigment epithelium-derived factor (PEDF) peptide in diabetic renal injury

“…P78-PEDF, a small PEDF peptide (15,18,21) (0.1 g·g Ϫ1 ·day Ϫ1 ) or vehicle (phosphate-buffered saline; PBS) were administered by continuous subcutaneous infusion beginning immediately after confirming the elevated blood glucose level via an osmotic minipump (no. 2006; Alzet, Durect, Palo Alto, CA), which delivered drug for 6 wk after a single pump placement as described previously (5,24,27). The condition of mice and body weight were monitored daily following the pump implantation.…”

“…Mean arterial pressure was measured using the Coda blood pressure system (Kent Scientific, Torrington, CT) (5,14,24). Mice were allowed to rest quietly for 10 min at 26°C.…”

“…Images were taken with the 100ϫ (oil) objective (total magnification, 1,000ϫ). Semiquantitative scores (0 -4) were assigned on the basis of masked reading as previously described (5,24,41). Briefly, each glomerulus on a kidney single section was graded from 0 to 4, where 0 represents no lesion; and 1, 2, 3, and 4 represent mesangial matrix expansion or sclerosis, involving Յ25, 25 to 50, 50 to 75, or Ͼ75% of the glomerular tuft area, respectively.…”

“…Urinary albumin excretion was measured by ELISA using Albuwell M (Exocell, Philadelphia, PA) as described previously (4,5,24). Urine creatinine was determined using a Creatinine Liquid Reagens Assay kit (Diazyme Laboratories, Poway, CA) as described previously (5,24).…”

“…Glomerular macrophage staining. Immunohistochemistry for macrophages was performed using rat anti-mouse Mac-2 antibody (clone M3/38; Cedarlane, Burlington, NC) on paraffin sections as described previously (5,24).…”