Antithrombin reduces ischemia/reperfusion-induced liver injury in mice by enhancing the activation of sensory neurons through protein kinase A activation

We recently demonstrated that antithrombin (AT) reduces ischemia/reperfusion (I/R)-induced liver injury in rats by increasing hepatic tissue levels of calcitonin gene-related peptide (CGRP), a neuropeptide released from the sensory nerve endings. In the present study, we examined the effect of AT on I/R-induced liver injury in wildtype mice (CGRP^+/+) and congenital α CGRP-deficient mice (CGRP^-/-). We further investigated whether AT affects CGRP release from dorsal root ganglion neurons (DRG) isolated from CGRP^+/+. Based on results obtained in the present study, we attempted to determine whether the anti-inflammatory activity of AT in vivo is dependent mainly on sensory neuron activation. AT enhanced I/R-induced increases in hepatic tissue levels of CGRP and 6-keto-PGF_1α a stable metabolite of PGI₂, in CGRP^+/+, while it did not enhance these increases in CGRP^-/-. AT inhibited reperfusion-induced increases in serum alanine aminotransferase levels by increasing hepatic tissue blood flow and by attenuating increases in hepatic levels of tumor necrosis factor and myeloperoxidase in CGRP^+/+, while it showed neither of these therapeutic effects in CGRP^-/-. AT increased CGRP release from cultured DRGs only in the presence of anandamide, and the AT-induced increase in CGRP release was not observed in the presence of KT5720, an inhibitor of protein kinase A (PKA). AT markedly increased intracellular levels of cAMP in the presence of anandamide. In conclusion, these results strongly suggest that AT might reduce I/R-induced liver injury by enhancing activation of the sensory neurons through activation of PKA in sensory neurons.