Inhibition of lymphocyte apoptosis by pancreatic stellate cells: impact of interleukin-15

Abstract

There is growing evidence that pancreatic stellate cells (PSCs) produce cytokines and take part in the regulation of inflammatory processes in the pancreas. IL-15 inhibits apoptosis of various cell populations. This study was performed to investigate whether PSCs produce IL-15 and thereby can affect lymphocytes. Primary PSCs were isolated from the rat pancreas using density gradient centrifugation. mRNA expression of IL-15 was demonstrated by RT-PCR, and IL-15 protein was analyzed by immunoblotting. Lymphocytes obtained from rat mesenterial lymph nodes were cocultured with in vitro activated PSCs. Apoptosis has been quantified by the binding of annexin V-FITC with a flow cytometer. Proliferation was monitored using [3H]thymidine incorporation. PSCs express two splice variants of IL-15. The protein was detectable only in cell lysates but not in the cell culture supernatant. Cocultivation of lymphocytes with PSCs and IL-15 inhibited spontaneous lymphocyte apoptosis, and this effect was reduced by an anti-IL-15 antibody. Lymphocytes induced vice versa the proliferation and collagen production of PSCs. The inhibition of spontaneous lymphocyte apoptosis in cocultures with PSCs was at least partially mediated by cell-bound IL-15. This effect and the stimulation of PSCs by lymphocytes may lead to a circulus vitiosus, resulting in the persistence of inflammatory processes and the development of fibrosis during chronic pancreatitis.

The pancreatic stellate cell: a star on the rise in pancreatic diseases

“…The involvement of PaSCs in the regulation of the inflammatory response during pancreatitis occurs, at least in part, through their production of chemokines and cytokines, as has been reported for myofibroblast-type cells in other tissues (65)(66)(67)(68). PaSCs have also been shown to have phagocytic activity in vivo and in cell culture (69) and therefore might also function as resident phagocytic cells during pancreatitis.…”

Bone marrow-derived pancreatic stellate cells in rats

“…The restoration process requires the deletion of cells that infiltrated and/or proliferated within the time of acute injury. The mechanisms of this 'tissue cleaning' are not fully understood; however, results generated by our group and others suggest that the apoptotic cell death may be substantially involved [4,22].…”

“…The isolation procedure was based on the high fat content in non-activated PSCs [1,2]. After mechanic and enzymatic dispersion of the pancreas, stellate cells were purified by isopycnic density centrifugation as previously described [22]. Isolated PSCs were suspended in IMDM supplemented with 10% FCS, 1% non-essential amino acids, 100 U/ml penicillin and 100 µg/ml streptomycin.…”

“…Protein extracts of PSCs were harvested as previously described [22]. Lysates were separated by SDS-polyacrylamide gel electrophoresis and blotted onto PVDF membrane.…”

Alcohol, Signaling, and ECM Turnover

“…The likely activating factors include proliferative and pro-fibrogenic growth factors such as platelet derived growth factor (PDGF) and TGF-b, as well as oxidant stress generated within the tissues by oxidative metabolism of alcohol to acetaldehyde and subsequently to acetate Masamune et al, 2002). Notably, PSCs can also synthesize endogenous cytokines resulting in an autocrine loop of cell activation (Shek et al, 2002;Sparmann et al, 2005). Due to the generally accepted fact that chronic alcohol administration is insufficient to cause overt pancreatic (and other tissue) injury in experimental animals, additional triggers such as LPS, may be needed to produce demonstrable tissue injury.…”