Background: Pancreatic fibrosis, a defining feature of chronic pancreatitis, is driven by pancreatic stellate cells (PSCs). Alcohol is known to activate PSCs, and once activated, they polarize macrophages to an M2 phenotype, resulting in a self-perpetuating cycle which further enhances PSC activation and fibrogenesis. Despite these observations, the underlying molecular mechanisms remain poorly understood. We hypothesize that alcohol-induced endoplasmic reticulum (ER) stress in PSCs promotes PSC-macrophage crosstalk, thereby exacerbating the progression of chronic alcoholic pancreatitis.
Methods: 1) Rat PSCs treated with ethanol, 10mM(E10) and 50mM(E50), were assessed for ER stress markers: eIF2⍺ and XBP1s, by RT-PCR.
2) PSCs were co-cultured with bone marrow derived macrophages(M) in Boyden chambers. Co-cultures were treated with E10, E50, and the ER stress inhibitor Tauroursodeoxycholic Acid 10 µM(U), alone or in combination, to study the effect on (a) PSC activation (assessed by collagen mRNA expression) and (b) macrophage polarisation (assessed by CD206 mRNA expression).
Results: All data expressed as fold change (meanSEM) over control.
1) XBP1s expression in PSCs was significantly increased by E10 and E50, while eIF2⍺ was significantly upregulated in PSCs by E50. XBP1s: E10: 2.80.57*; E50: 8.1****. *p<0.05, ****p<0.001 vs Control]. eIF2⍺ [E10: 1.50.25; E50: 2.6**. **p<0.01 vs Control].
2) In the PSC-macrophage co-culture setting, a) E10 significantly increased collagen expression in PSCs; this inductive effect was reduced in the presence of U. [E10: 2.60.35**; U: 1.3E10+U: 1.8. **p<0.01 vs Control].
b) CD206 expression in macrophages was significantly reduced in the presence of U. [E10: 1.1041; U: 0.360.12**E10+U: 0.58*. **p<0.01 vs Control, *p<0.05 vs E10].
Conclusion: Alcohol induces endoplasmic reticulum (ER) stress in PSCs, as evidenced by the upregulation of eIF2⍺ and XBP1s. In the PSC-macrophage co-culture setting, alcohol exposure leads to PSC activation and macrophage polarization, indicated by increased expression of collagen and CD206, respectively. Notably, treatment with an ER stress inhibitor reversed these changes, highlighting the role of ER stress in mediating alcohol-induced PSC-macrophage interactions.
Implication: These findings suggest that targeting ER stress may offer a promising therapeutic strategy for mitigating fibro-inflammatory responses and arresting the progression of alcoholic chronic pancreatitis.