D. Bleich et al., INTERLEUKIN-1-BETA REGULATES THE EXPRESSION OF A LEUKOCYTE TYPE OF 12-LIPOXYGENASE IN RAT ISLETS AND RIN M5F CELLS, Endocrinology, 136(12), 1995, pp. 5736-5744
The leukocyte type of 12-lipoxygenase (12-LO) may play a role in infla
mmatory reactions in many cell types through the conversion of arachid
onic acid to proinflammatory eicosanoids that include 12-hydroperoxyei
cosatetraenoic acid and 12-hydroeicosatetraenoic acid. Previous studie
s demonstrating the presence of a functional 12-LO pathway in rat and
human pancreatic beta-cells plus the recent cloning of a rat leukocyte
type of 12-LO allowed us to evaluate whether inflammatory cytokines s
uch as interleukin-1 beta (IL-1 beta) can regulate the beta-cell 12-LO
enzyme pathway, thus providing a potential link between the cytotoxic
effects of cytokines on pancreatic beta-cells and the proinflammatory
effects of 12-LO products. We demonstrate that IL-1 beta induces 12-L
O protein and messenger RNA (mRNA) expression in RIN m5F cells and 12-
LO mRNA expression in rat islets. RIN m5F cells treated for 16 h with
IL-1 beta (25, 50, and 100 ng/liter) showed a maximal 2-fold increase
in the expression of a leukocyte form of 12-LO demonstrated by Western
blots. A concomitant increase in 12-LO mRNA expression was seen at th
is time point using a highly sensitive competitive polymerase chain re
action assay. The increase in mRNA and protein expression was preceded
by increased 12-LO pathway activity measured by a RIA for 12-S-HETE.
Separate experiments using purified Sprague-Dawley rat islets also sho
wed increased expression of 12-LO mRNA and enzyme activity in response
to IL-1 beta. These results demonstrate that IL-1 beta can upregulate
12-LO expression and activity in rat beta-cells.