p-JAK2 plays a key role in catalpol-induced protection against rat intestinal ischemia/reperfusion injury

Catalpol, an iridoid glucoside isolated from the radix of Rehmannia glutinosa Libosch, is found to have a wide variety of biological activities. Based on our pre-experiments, we proposed that catalpol pretreatment could protect against intestinal ischemia/reperfusion (I/R) injury and the JAK2/STAT3 signaling pathway might play an important role in the protection. Both in vivo intestinal I/R-injured rats and in vitro hypoxia/reoxygenation (H/R)-injured IEC-6 cells were used in the present study. The results confirmed our proposal. The in vivo results showed that catalpol (25, 50 mg kg(-1)) significantly attenuated rat intestinal I/R injury by decreasing pro-inflammatory cytokines, reducing oxidative stress, and restoring intestinal barrier function without affecting the corresponding controls. Catalpol pretreatment significantly increased the Bcl-2/Bax ratio, and decreased cleaved caspase3, p-JAK2, and p-STAT3 protein expression without affecting total JAK2 and STAT3 in vivo and in vitro, showing that catalpol inhibited apoptosis through selectively inhibiting p-JAK2 and p-STAT3. In vitro studies indicated that catalpol (40 mM) pretreatment significantly and selectively inhibited p-STAT3 nuclear translocation and transfection of JAK2 siRNA significantly decreased JAK2, p-JAK2, STAT3, p-STAT3, and other apoptosis-related proteins in H/R-injured IEC-6 cells, suggesting that JAK2 siRNA partially simulated the effects of catalpol on apoptosis-related proteins. JAK2 siRNA + catalpol could not further decrease JAK2, p-JAK2, STAT3, p-STAT3, and other apoptosis-related proteins, suggesting that inhibition of the JAK2/STAT3 signaling pathway plays a key role in catalpol-induced protective effects. Our results suggest that p-JAK2 is the key target in catalpol-induced protection against intestinal I/R injury, providing information for further translational studies.