Interleukin-1 beta regulates the expression of a leukocyte type of 12-lipoxygenase in rat islets and RIN m5F cells.

Abstract

The leukocyte type of 12-lipoxygenase (12-LO) may play a role in inflammatory reactions in many cell types through the conversion of arachidonic acid to proinflammatory eicosanoids that include 12-hydroperoxyeicosatetraenoic acid and 12-hydroeicosatetraenoic acid. Previous studies 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 such 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-LO 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 this time point using a highly sensitive competitive polymerase chain reaction 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 showed increased expression of 12-LO mRNA and enzyme activity in response to IL-1 beta. These results demonstrate that IL-1 beta can up-regulate 12-LO expression and activity in rat beta-cells.

Expression of arachidonate platelet‐type 12‐lipoxygenase in human rheumatoid arthritis type B synoviocytes

“…After demonstrating the expression of a platelet 12‐LOX in human RA type B synoviocytes, we characterized effects of IL‐1β, IL‐4, IL‐6 and TNFα on this enzyme activity. Our results showed that IL‐1β increased 12‐HETE production (4‐fold) as observed in RIN m5F insulinoma cells [33]and in isolated pancreatic islets [43]. We also observed an increase in 12‐HETE production (2.5‐fold) after incubation of human RA type B synoviocytes with TNFα.…”

“…We also demonstrated 12‐LOX expression in human RA type B synoviocytes by RT‐PCR in situ (data not shown) and the presence of 12‐LOX protein was confirmed by immunofluorescence. Moreover, our data showed that treatment of human RA type B synoviocytes with IL‐1β markedly increased the cellular expression of 12‐LOX protein as observed in RIN m5F insulinoma cells [33].…”

ALOX12 in Human Toxoplasmosis

“…This suggests an interplay between the roles of ALOX12 and NALP1 in controlling T. gondii infection in human monocytic cells. Interestingly, IL-1␤ has also been shown to be an upregulator of ALOX12 expression in rat pancreatic beta cells (22). Earlier, Henderson and colleagues found that T. gondii altered eicosanoid release by human mononuclear phagocytes (23).…”

Targeting 12-lipoxygenase as a novel strategy to combat the effects of inflammation on beta cells in diabetes

“…Lipoxygenases are implicated in various inflammatory diseases, including cancer, heart disease, asthma and diabetes [17]. Indeed, Nadler and colleagues, and others, have been investigating the role of leucocyte 12-lipoxygenase in diabetes since the mid-1990s [18,19]. 12-Lipoxygenase peroxidates polyunsaturated fatty acids, including arachidonic acid and linoleic acid to generate lipid inflammatory mediators, such as 1 2 -h y d r o p e r o x y e i c o s a t e t r a e n o i c a c i d a n d 1 2hydroxyeicosatetraenoic acid (12-HETE).…”