Regulation of the expression of group IIA and group V secretory phospholipases A(2) in rat mesangial cells

Rat mesangial cells synthesize and secrete a secretory phospholipase A(2) u pon stimulation of the cells with cytokines, like IL-1 beta and TNF and wit h cAMP elevating agents like forskolin. This enzyme was previously characte rized to belong to group IIA sPLA(2). The discovery of several other low mo lecular weight phospholipases, like group IIC in murine testis and group V in human and rat heart, prompted investigations on the presence of group II C and group V sPLA(2) in rat mesangial cells. This was done by isolating th e RNA from stimulated cells and performing RT-PCR, using primers specific f or group IIC and V sPLA(2). The results indicate that rat mesangial cells u pon stimulation express next to group IIA also group V sPLA(2). No indicati ons were obtained for the expression of group IIC sPLA(2). The regulation o f the expression of group V sPLA(2) at the mRNA level was further investiga ted by examining the time-dependent expression, the influence of dexamethas one and the signaling route of the IL-1 beta stimulation. The results show that the IL-1 beta induced expression of group V sPLA(2) mRNA was time depe ndent and, similar to that of group IIA sPLA(2) mRNA, involves activation o f NF-kappa B. However, in contrast to the group IIA sPLA(2), the expression of group V sPLA(2) was not influenced by the presence of dexamethasone. Th e expression of both phospholipases was also examined at the protein level in stimulated mesangial cells. Western blot analysis shows that stimulated mesangial cells synthesize both group IIA and group V sPLA(2) protein but t he expression of group V is lower compared to that of group IIA sPLA(2). In addition, the extent of secretion into the medium appears to be considerab ly higher for group IIA than for group V sPLA(2). (C) 2000 Elsevier Science B.V. All rights reserved.