Inhibition of intracellular angiotensin II formation blocks high glucose effect on mesangial matrix.
High glucose causes increased matrix synthesis by glomerular mesangial cells and angiotensin II (Ang II) has been shown to mediate this effect of glucose. These studies investigate whether inhibition of Ang II formation can block high glucose-induced increase in mesangial matrix. Human mesangial cells were incubated with 25 mM glucose (HG) along with captopril, an ACE inhibitor, to block Ang II formation. In other experiments, cells were nucleofected with siRNA to knockdown angiotensinogen (Agt), the precursor of Ang II, and then exposed to high glucose. Captopril blocked high glucose-induced increase in Ang II levels in the cell media (extracellular) but failed to inhibit it in the cell lysate (intracellular). Moreover, captopril treatment did not block the stimulatory effect of high glucose on TGF-beta1 and fibronectin. In contrast, knockdown of the Agt gene prevented high glucose-induced increase in both extracellular and intracellular Ang II levels, and was accompanied by normalization of TGF-beta1 and fibronectin. These data suggest that intracellular Ang II may play an important role in the mediation of the high glucose effect on matrix and that ACE inhibitors may not be effective in blocking intracellular Ang II formation in mesangial cells.
Singh
Rekha
R
Hines VA Hospital, Hines, IL 60141, USA. Rekka.singh@va.gov
Choubey
Divaker
D
Chen
Jianming
J
Leehey
David J
DJ
D000804:Angiotensin II / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000808:Angiotensinogen / Q000235:genetics; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D005353:Fibronectins / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
D000806:Angiotensin-Converting Enzyme Inhibitors; D017931:DNA Primers; D005353:Fibronectins; D053773:Transforming Growth Factor beta1; D000808:Angiotensinogen; D000804:Angiotensin II; D005947:Glucose