IgA immune complex blunts the contraction of cultured mesangial cells through the inhibition of protein kinase C and intracellular calcium.
The effects of IgA immune complex (IgA-IC) on the contractile function of cultured mesangial cells were measured by the changes in planar surface area in response to treatment with agonists. Incubation of mesangial cells with IgA-IC for 24 hours significantly decreased the contractile responses to angiotensin II (10(-6) M) and phorbol 12-myristate 13-acetate (PMA, 10(-6) M). Pretreatment of mesangial cells with the protein kinase C (PKC) inhibitor, chelerythrine (10(-6) M), eliminated the difference in contractile responses to angiotensin II or PMA between the control and IgA-IC groups indicating IgA-IC may inhibit the activity of PKC. The contractile responses to ionomycin were not significantly different between IgA-IC treated and control mesangial cells, suggesting that the contractile machinery is not impaired by IgA-IC. Intracellular calcium, [Ca2+]i measured by changes in fura-2 level in response to ATP or bradykinin, was significantly inhibited in IgA-IC treated mesangial cells, compared to control cells. In contrast, treatment with thapsigargin did not result in significant differences in [Ca2+]i between IgA-IC and control mesangial cells, suggesting that a negligible role of endoplasmic reticulum in the effects of IgA-IC. Using PKC specific antibodies, IgA-IC significantly increased the particulate fraction of PKC-iota of mesangial cells to 141+/-13% of control, without significantly changing the protein content of PKC-alpha, -delta and -lambda in the cytosolic and particulate fractions. In summary, IgA-IC inhibits the contractile responses of cultured mesangial cells to agonists by inhibiting the activation of PKC and [Ca2+]i.
Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, National Defense University, Taipei (114), Taiwan, Republic of China. jsjin@ndmctsgh.edu.tw
Jong-Shiaw
JS
Jin
Chen-Wen
CW
Yao
Shuk-Man
SM
Ka
Ting-Yu
TY
Chin
Sheau-Huei
SH
Chueh
Herng-Sheng
HS
Lee
Lai-Fa
LF
Sheu
Yeh-Feng
YF
Lin
Wei-Hwa
WH
Lee
Ann
A
Chen
D000470:Alkaloids; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D053119:Benzophenanthridines; D002118:Calcium / Q000037:antagonists & inhibitors*; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D015151:Immunoblotting; D007070:Immunoglobulin A / Q000494:pharmacology*; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013778:Tetrazolium Salts; D013844:Thiazoles
D000470:Alkaloids; D053119:Benzophenanthridines; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D007070:Immunoglobulin A; D007476:Ionophores; D007527:Isoenzymes; D010617:Phenanthridines; D013778:Tetrazolium Salts; D013844:Thiazoles; D000804:Angiotensin II; D015759:Ionomycin; C016299:chelerythrine; D011493:Protein Kinase C; C022616:thiazolyl blue; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium