- 作者: Jin-Shuen Chen; Herng-Sheng Lee; Jong-Shiaw Jin; Ann Chen; Shih-Hua Lin; Shuk-ManKa; Yuh-Feng Lin
- 作者服務機構: Graduate Institute of Medical Sciences, Graduate Institute of Life Sciences, National Defense Medical Center, Division of Nephrology, Department of Internal Medicine, and Department of Pathology, Tri-Service General Hospital, Taipei, Taiwan, ROC
- 中文摘要: --
- 英文摘要: Hyperglycemia and mannitol activate protein kinase C(PKC) and induce mesangial cell hypocontractility thatsubsequently may modulate renal function. Since focaladhesion kinase(FAK) activation is known to be linkedwith PKC activity, FAK may also be involved in mesan-gial cell contraction.To facilitate our understanding ofthe PKC- and FAK-modulating mechanism, we devel-oped an in vitro model of mouse mesangial cell hypo-contractility induced by hyperglycemia or mannitol.Mouse mesangial cells(CRL-1927)were exposed to:nor-mal D-glucose(group N),high D-glucose(group H),andcontrol groups at the same osmolality as H plus L-glu-cose(group L) and mannitol(group M).Changes in theplanar surface area of cells in response to 1 uM phorbol12-myristate 13-acetate(PMA) were determined. West-ern blot analyses for PKC, phosphorylated(p)-PKC, tyro-sine phosphorylation,FAK, and p-FAK were done oneach of these four groups. The effects of mannitol in var-ious doses on cell contraction and activation of PKC andFAK were also assayed. The planar surface areas ofgroups H and M both showed an attenuated change inresponse to PMA stimulation. Before PMA stimulation,the baseline PKC expression of groups H and M showeda higher expression of p-PKCα and δ than that seen ingroup N(p<0.05).Results of tyrosine phosphorylationand immunoprecipitation showed that FAK may be in-volved in this contraction process. The total amount ofFAK showed no significant difference among the fourexperimental groups; however, p-FAK was found to havesignificantly increased in group M(p<0.05). The use ofPKC and tyrosine kinase inhibitors reduced PMA-in-duced mesangial cell contraction in all four groups. Acti-vation of PKCα, δ, and FAK with the resultant inhibition ofmesangial cell contraction by mannitol was found to bedose-dependent. These results may provide a correla-tion between increased expression of several PKC iso-forms and,in particular, increased phosphorylation lev-els of PKCα and δ and hypocontractility induced by highglucose and mannitol treatment. Furthermore, the man-nitol-induced hypocontractility involving PKC and FAKoccurred in a dose-dependent manner.
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