Activin in acute pancreatitis: Potential risk-stratifying marker and novel therapeutic target

Abstract

Acute Pancreatitis is a substantial health care challenge with increasing incidence. Patients who develop severe disease have considerable mortality. Currently, no reliable predictive marker to identify patients at risk for severe disease exists. Treatment is limited to rehydration and supporting care suggesting an urgent need to develop novel approaches to improve standard care. Activin is a critical modulator of inflammatory responses, but has not been assessed in pancreatitis. Here, we demonstrate that serum activin is elevated and strongly correlates with disease severity in two established murine models of acute pancreatitis induced by either cerulein or IL-12 + IL-18. Furthermore, in mice, inhibition of activin conveys survival benefits in pancreatitis. In addition, serum activin levels were measured from a retrospective clinical cohort of pancreatitis patients and high activin levels in patients at admission are predictive of worse outcomes, indicated by longer overall hospital and intensive care unit stays. Taken together, activin is a novel candidate as a clinical marker to identify those acute pancreatitis patients with severe disease who would benefit from aggressive treatment and activin may be a therapeutic target in severe acute pancreatitis.

Figure 1

Activin levels are increased in a cerulein-induced model of acute pancreatitis. Panel A: Time course of cerulein treatment (hours) with activin serum levels obtained by ELISA and compared to vehicle treated controls as described in Methods. n = 4 for all groups except for 24 hours timepoint where n = 5, p = 0.026 per ANOVA with Dunnet’s post-test. Panel B: ELISA indicating serum amlyase (U/L) compared to activin levels for each cerulein-treated mouse. n = 13; r = 0.69, p < 0.05 per Pearson product-moment correlation coefficient. Panel C: ELISA of serum IL6 (pg/ml) compared to activin levels for each cerulein-treated mouse. n = 13, r = 0.818, p < 0.001 per Pearson product-moment correlation coefficient.

Figure 2

Activin levels are strongly increased in a model of severe necrotizing pancreatitis. Wild type and ob/ob animals were treated with IP injections of IL-12 + IL-18 on subsequent days as described in Methods, which leads to severe necrotizing pancreatitis in the ob/ob mice and mild pancreatitis in the control mice. Panel A: Serum activin levels measured by ELISA in wild-type compared to ob/ob mice (p < 0.01). n = 25 for wildtype and n = 21 for ob/ob animals, p < 0.05 per t-test Panel B: Serum activin levels in wild-type (gray bars) and ob/ob (red bars) at increasing time points. n = 5 per group except 72 hours in the ob/ob group where n = 1 due to mortality. ANOVA plus Dunnet’s post-test for statistical testing. Panel C: H/E stain of wild-type and ob/ob pancreas after 24 hours of IL-12 + IL-18 treatment. Panel D: Macroscopic necrosis score compared to activin serum levels. n = 46; r = 0.903, p < 0.0001 per Pearson product-moment correlation coefficient. Panel E: Compound histologic score compared to activin serum levels. n = 46; r = 0.5722, p < 0.001 per Pearson product-moment correlation coefficient.

Figure 3

Activin inhibition through activin neutralizing antibody treatment is protective against mortality in acute pancreatitis. Ob/ob animals where pretreated for 30 minutes with either anti-activin antibody (red line, n = 10) or non-specific IgG (black line, n = 9) before administration of IL12 + IL18 and 24 hours after the last IL12 + IL-18 administration. Live animals were recorded on each day for one week. Hazard ratio 0.146 (0.028 to 0.7251) for anti-activin antibody versus non-specific IgG, p = 0.0189 per Mantel-Cox test.

Figure 4

In patients with acute pancreatitis, activin is increased in moderate and severe disease and increased activin correlates with worse prognosis. Panel A: Serum collected from admission and two subsequent days was collected from each pancreatitis case in the cohort and serum activin measured by ELISA. Similarly, samples from one time point from healthy controls were collected and serum activin compared to pancreatitis cases. n = 30 for controls and n = 90 for cases, p < 0.001 per t-test. Panel B: Pancreatitis samples are grouped by severity as per revised Atlanta criteria (controls are open diamonds, mild are light gray diamonds, moderate are gray diamonds and severe pancreatitis are black diamonds). n = 30 per group, ANOVA plus Dunnet’s post-test used for statistical testing. Panel C: Cases were grouped by activin levels at admission with cut-offs at 25% and 75% percentile. Average length of ICU stay is shown for each group. n = 16 for intermediate and n = 7 for activin high and low groups. ANOVA plus Dunnet’s post-test used for statistical analysis. Panel D: ROC analysis for distinguishing mild versus severe pancreatitis using admission activin levels n = 20, AUC 0.820.