Intercellular Adhesion Molecule-1 Deficiency Is Protective against Nephropathy in Type 2 Diabetic db/db Mice

Kidney intercellular adhesion molecule-1 (ICAM-1) expression in diabetic db/db mice. Immunoperoxidase staining identified weak expression of ICAM-1 in glomerular and peritubular capillaries and on the tubular brush border of (A) a nondiabetic db/+ mouse. In comparison, ICAM-1 expression was increased in glomeruli and on the tubular brush border in diabetic db/db mice at age (B) 2 mo and (C) 8 mo. As expected, ICAM-1 was absent in a diabetic kidney from (D) an 8-mo-old ICAM-1^−/− db/db mouse. Magnification: ×400.

ICAM-1 deficiency reduces kidney macrophage accumulation and histologic damage in diabetic db/db mice. Immunostaining for CD68 in 8-mo-old mice shows very few macrophages in (A) a normal db/+ mouse kidney, which is markedly increased in the glomeruli and interstitium of (B) a diabetic db/db mouse kidney. (C) An ICAM-1^−/− db/db mouse with equivalent diabetes has a reduced accumulation of kidney macrophages. Histologic staining with periodic acid-Schiff (PAS) and hematoxylin shows the normal kidney structure of (D) a nondiabetic db/+ mouse at 8 mo. In comparison, there is significant damage to glomeruli (hypertrophy, hypercellularity, mesangial PAS deposits) and tubules (dilation, atrophy) in (E) a diabetic db/db mouse at 8 mo, which is attenuated in (F) an equally diabetic ICAM-1^−/− db/db mouse at the same age. Magnification: ×400.

ICAM-1 deficiency reduces albuminuria in diabetic db/db mice. Urinary albumin excretion rate (UAER) was evaluated at 2-mo intervals from ages 2 to 8 mo in db/+, db/db, and ICAM-1^−/− db/db mice. From age 6 mo, ICAM-1^−/− db/db mice have significantly less albuminuria than db/db mice. Data = mean ± SEM; n = 10; **P < 0.01 versus db/+; ^#P < 0.05, ^##P < 0.01 versus db/db.

ICAM-1 deficiency decreases renal fibrosis in diabetic db/db mice. Kidney immunostaining in 8-mo-old mice identified weak glomerular and tubular expression of TGF-β1 in (a) a nondiabetic db/+ mouse. Increased levels of glomerular, tubular, and interstitial TGF-β1 were observed in the diabetic kidney of (b) a db/db mouse, but were noticeably reduced in (c) an ICAM-1^−/− db/db mouse. Collagen IV immunostaining was present in the mesangium and basement membranes of (d) a nondiabetic db/+ mouse. Increased glomerular and interstitial collagen IV were detected in the diabetic kidney of (e) a db/db mouse, but were diminished in (f) an ICAM-1^−/− db/db mouse. Immunostaining of α-smooth muscle actin was detected in kidney vessels in (g) a nondiabetic db/+ mouse. Many interstitial cells expressing α-smooth muscle actin were identified in the diabetic kidneys of (h) a db/db mouse, and these cells were markedly reduced in (i) an ICAM-1^−/− db/db mouse. Magnification: a to c, ×400; d to i, ×250.

Interstitial macrophages in diabetic kidneys express TGF-β1. Double immunostaining shows three peritubular F4/80+ macrophages (brown) expressing TGF-β1 (blue) in a diabetic db/db mouse at age 8 mo. Magnification: ×1000.

Macrophages stimulated with high glucose or advanced glycation end products (AGE) produce more active TGF-β1. Cell supernatant was collected from 1 × 10⁶ bone marrow-derived macrophages cultured for 72 h in serum-free medium containing low glucose (5 mmol/L), high glucose (25 mmol/L), control BSA (CTL-BSA, 200 μg/ml) or carboxymethyllysine BSA (CML-BSA, 200 μg/ml). Supernatants were assessed by ELISA for levels of (a) active TGF-β1 and (b) total (active and latent) TGF-β1 after acid treatment. Data = mean ± SD; n = 3; **P < 0.01, ***P < 0.001 versus 5 mmol/L glucose; ^#P < 0.05 versus CTL-BSA.