Hyperhomocysteinemia (hHcys) enhances
ceramide production, leading to the activation of
NADPH oxidase and consequent glomerular oxidative stress and
sclerosis. The present study was performed to determine whether
acid sphingomyelinase (Asm), a
ceramide-producing
enzyme, is implicated in the development of hHcys-induced glomerular oxidative stress and injury. Uninephrectomized Asm-knockout (Asm(-/-)) and wild-type (Asm(+/+)) mice, with or without Asm
short hairpin RNA (
shRNA) transfection, were fed a
folate-free (FF) diet for 8 weeks, which significantly elevated the plasma Hcys level compared with mice fed normal chow. By using in vivo molecular imaging, we found that transfected shRNAs were expressed in the renal cortex starting on day 3 and continued for 24 days. The FF diet significantly increased renal
ceramide production, Asm
mRNA and activity, urinary total
protein and
albumin excretion, glomerular damage index, and
NADPH-dependent
superoxide production in the renal cortex from Asm(+/+) mice compared with that from Asm(-/-) or Asm
shRNA-transfected wild-type mice. Immunofluorescence analysis showed that the FF diet decreased the expression of
podocin but increased
desmin and
ceramide levels in glomeruli from Asm(+/+) mice but not in those from Asm(-/-) and Asm
shRNA-transfected wild-type mice. In conclusion, our observations reveal that Asm plays a pivotal role in mediating podocyte injury and glomerular
sclerosis associated with
NADPH oxidase-associated local oxidative stress during hHcys.