Cyclooxygenase-2 is required for activated pancreatic stellate cells to respond to proinflammatory cytokines

Abstract

Cyclooxygenase-2 (COX-2) mediates various inflammatory responses and is expressed in pancreatic tissue from patients with chronic pancreatitis. To examine the role of COX-2 in chronic pancreatitis, we investigated its participation in regulating functions of pancreatic stellate cells (PSCs), using isolated rat PSCs. COX-2 was expressed in culture-activated PSCs but not in freshly isolated quiescent PSCs. TGF-beta1, IL-1beta, and IL-6 enhanced COX-2 expression in activated PSCs, concomitantly increasing the expression of alpha-smooth muscle actin (alpha-SMA), a parameter of PSC activation. The COX-2 inhibitor NS-398 blocked culture activation of freshly isolated quiescent PSCs. NS-398 also inhibited the enhancement of alpha-SMA expression by TGF-beta1, IL-1beta, and IL-6 in activated PSCs. These data indicate that COX-2 is required for the initiation and promotion of PSC activation. We further investigated the mechanism by which cytokines enhance COX-2 expression in PSCs. Adenovirus-mediated expression of dominant negative Smad2/3 inhibited the increase in expression of COX-2, alpha-SMA, and collagen-1 mediated by TGF-beta1 in activated PSCs. Moreover, dominant negative Smad2/3 expression attenuated the expression of COX-2 and alpha-SMA enhanced by IL-1beta and IL-6. Anti-TGF-beta neutralizing antibody also attenuated the increase in COX-2 and alpha-SMA expression caused by IL-1beta and IL-6. IL-6 as well as IL-1beta enhanced TGF-beta1 secretion from PSCs. These data indicate that Smad2/3-dependent pathway plays a central role in COX-2 induction by TGF-beta1, IL-1beta, and IL-6. Furthermore, IL-1beta and IL-6 promote PSC activation by enhancing COX-2 expression indirectly through Smad2/3-dependent pathway by increasing TGF-beta1 secretion from PSCs.

PGE2 regulates pancreatic stellate cell activity via the EP4 receptor

“…However, key experiments were repeated with primary stellate cells which confirmed the observations. Our studies support the suggestion that HPSCs cells express COX-2 and secrete PGE 2 (22). More importantly, we found that PGE 2 is a powerful regulator of stellate cells that increases their proliferation, migration and the production of extra cellular matrix (ECM) molecules.…”

Reclassification of tumour origin in resected periampullary adenocarcinomas reveals underestimation of distal bile duct cancer

“…4). 76 , transforming growth factor-ß (TGFß) 70;77 , interleukin -1 ß (Il-1ß) 78 and epidermal growth factor (EGF) 79 are some of the factors which regulate proliferation, activation, collagen production and apoptosis in the pancreatic stellate cell.…”

Signal transduction in pancreatic stellate cells

“…It has been shown that pancreatic cancer cells are also a source of PSC-activating factors [6][7][8]. The effects of IL-1 and IL-6 on the initiation of PSCs activation might be indirect, through the TGF-b1 production [19]; anti-TGF-b1 neutralizing antibody attenuated a-SMA expression induced by IL-1b and IL-6 [19]. Importantly, PSCs by themselves are capable of synthesizing cytokines, such as TGF-b1, activin A, and IL-1, suggesting the existence of autocrine loops that may contribute to the perpetuation of PSC activation after an initial exogenous signal, thereby promoting the development of pancreatic fibrosis [10][11][12][13].…”

“…In addition to the Smad-dependent pathway, Smadindependent TGF-b signaling pathways exist, for example, MAP kinases, such as ERK. Thus, TGF-b1 intracellular signaling occurs via Smad-dependent and Smad-independent pathways [19].…”

“…Another autocrine loop may exist between IL-6 and TGF-b1 through ERK-and Smad2/3-dependent pathways in activated PSCs [75]. Interestingly, it has been recently shown that cyclooxygenase-2 expression, induced by TGF-b1 through Smad2/ 3-dependent pathways, is required for activated PSCs to respond to proinflammatory cytokines [19].…”