Background: Smoking accelerates the progression of alcoholic chronic pancreatitis, evidenced by early calcification and fibrosis (associated with the activation of pancreatic stellate cells (PSC)). However, the mechanisms mediating these effects are unknown. Previous studies showed that Simvastatin can inhibit PSC activation, and that fibrogenic PSC-macrophage interactions are mediated by IL4. We hypothesise that Simvastatin and/or IL4 blockade can inhibit the PSC-macrophage driven fibro-inflammatory response and arrest the progression of alcoholic chronic pancreatitis.
Methods: In-vivo: Rats were alcohol-fed(A) for 15 weeks, exposed to cigarette smoke(S) from week 5, and challenged with LPS (L, 3 mg/kg weekly-IV weeks 9,10,11), to establish pancreatitis. Animals were then divided into: i) ASL+V(vehicle); ii) ASL+Sim(Simvastatin), 20 mg/kg daily for the last 4 weeks; iii) ASL+BP(IL-4 Blocking Peptide), 3 mg/kg, IP once/day for the last 4 weeks; and iv) ASL+Sim+BP; (n=4/group). Pancreatic injury and fibrosis were assessed by morphometry.
In-vitro: (a) PSCs (n=4) exposed to 50mM ethanol(A) and Sim(1,2.5,5and10µM), were assessed for collagen expression. (b) PSCs (n=4) co-cultured with bone-marrow-derived macrophages(M) in the presence of 50mMA, 40ng/ml CSE(S), 5 µM Sim and 1.5 µM BP were assessed for PSC activation.
Results: In-vivo: Simvastatin significantly decreased AS-induced pancreatic injury in rats. BP and Sim+BP treatment exhibited a trend towards reduced injury albeit not statistically significant [Injury scores mean±SEM: ASL+V: 34.65±4.1; ASL+Sim: 17.13±1.1*; ASL+BP: 25.18±3.1; ASL+Sim+BP: 27.84±4.2. *p<0.05 ASL+BP vs ASL+V].
In-vitro: (a) Alcohol-induced collagen expression in PSCs was significantly downregulated by Simvastatin. [Fold change mean±SEM: Control: 1; A: 2.4±0.35; A+Sim(1µM): 2.2±0.15; A+Sim(2.5µM): 1.8±0.094; A+Sim(5µM): 1.4±0.28*; AS+Sim(10µM): 1±0.6**. *p<0.05, **p<0.01 vs Control].
(b) Sim+BP arrested PSC activation in AS-exposed PSC-M co-cultures. [Fold change mean±SEM: AS: 1; AS+Sim: 0.66±0.21; AS+BP: 0.48±0.12; AS+Sim+BP: 0.24±0.16*. *p<0.05 vs AS].
Conclusion: Simvastatin reversed established alcohol and smoking-induced pancreatic injury in rats and inhibited alcohol-induced collagen expression in PSCs. Moreover, in the presence of macrophages, Sim+BP significantly attenuated AS-induced collagen expression in PSCs, suggesting a disruption of PSC-macrophage interaction.
Implication: Simvastatin and/or IL4 blockade may represent a potential therapeutic strategy for arresting the progression of chronic alcoholic pancreatitis.