Modulation of tissue inflammatory response by histamine receptors in scorpion envenomation pathogenesis: involvement of H4 receptor.

The inflammatory response caused by scorpion venoms is a key event in the pathogenesis of scorpion envenomation. This response was assessed in the cardiac, pulmonary, and gastric tissues of envenomed mice. The results reveal an increase of permeability in cardiac, pulmonary, and gastric vessels accompanied by an edema-forming, inflammatory cell infiltration, and imbalanced redox status. These effects are correlated with severe tissue alterations and concomitant increase of metabolic enzymes in sera. Pretreatment of mice with antagonists of H1, H2, or H4 receptors markedly alleviated these alterations in the heart and lungs. Nevertheless, the blockade of the H3 receptor slightly reduced these disorders. Histamine H2 and H4 receptors were the most pharmacological targets involved in the gastric oxidative inflammation. These findings could help to better understand the role of histamine in scorpion venom-induced inflammatory response and propose new therapy using as targets the H4 receptor in addition to histamine H1 and H2 receptors to attenuate the induced inflammatory disorders encountered in scorpion envenoming.