Estimulação elétrica da via anti-inflamatória colinérgica protege da doença do enxerto-versus-hospedeiro (GVHD)

Abstract

Graft-versus-host disease (GVHD) is a systemic inflammatory syndrome that occurs after allogeneic hematopoietic stem cell transplantation. This disease affects GVHD target organs, including liver, intestine and spleen. The cholinergic anti-inflammatory pathway (CAIP), a neurological mechanism capable of controlling peripheral inflammation through the vagus nerve, has been shown to be important in immune system modulation and reducing inflammation in several models of inflammatory diseases such as colitis, sepsis and rheumatoid arthritis. However, there are no studies exploring this neuroimmune regulation in GVHD. Therefore, the aim of this study was to evaluate the role of the cholinergic anti-inflammatory pathway in modulation of the GVHD inflammatory response. Acute GVHD was induced by transplant of allogeneic bone marrow cells and splenocytes from Balb/c mice to C57BL/6J in GVHD and GVHD+VNS groups. Mice that received bone marrow cells and splenocytes from syngeneic animals (C57BL/6J) did not develop any disease and were considered the control group. To analyze the CAIP stimulation, GVHD+VNS mice were subjected to vagus nerve electrical stimulation (VNS) 6 hours before the transplant. The liver and intestine were processed for histopathological analysis and the stimulated animals showed reduced intestinal and hepatic injury, while the animals in the GVHD group had severe intestinal injuries leading the loss of the organ architecture and a proeminent inflammatory infiltrate in the liver. ELISA assays for the main inflammatory cytokines and chemokines were also performed and the GVHD+VNS group presented an increase in intestinal levels of IL-10, TNF-α and CCL2 and a decrease in hepatic levels of CCL2, CCL5 and TNF-α. We also observed a reduction in splenic atrophy in GVHD+VNS mice. N-acetil-β-D-glicosaminidase (NAG), myeloperoxidase (MPO) and peripheral blood smear assays were performed to quantify the total and differential leukocytes in the intestine, liver, spleen and blood. The mice that received electrical stimulation showed a reduction in the infiltrate of neutrophils in the spleen and macrophages in the liver. Moreover, there was a reduction in lymphopenia and neutrophilia related to GVHD in the GVHD+VNS group. Cardiac function was also analyzed by echocardiogram and in the GVHD+VNS group, we observed a prevention of cardiac damage related to graft-versus-host disease. Finally, recipient mice were clinically evaluated with a standard scoring system and monitored for mortality. Electrical stimulation resulted in effective protection from GVHD, reducing clinical signs and lethality of the disease. Altogether, our results demonstrated that the activation of the cholinergic anti-inflammatory pathway contributes to regulation of inflammatory response and severity related to GVHD. Thus, VNS has a potential therapeutic application in graft-versus-host disease treatment.