The effect of endomorphins-1, -2 on the production of reactive oxygen species and the absorption activity of innate immunity cells <i>in vitro</i> and <i>in vivo</i>

Abstract

   Background. A high percentage of people in the world suffer from acute or chronic pain, the treatment of which is based on the introduction of morphine and its derivatives, agonists of the µ-opioid receptors, leading to the development of addiction in patients. An urgent task is to study the properties of endogenous opioid peptides, which are capable of showing not only pronounced analgesic activity, but also have a number of other effects on the periphery, while having a much smaller spectrum of side effects. Of particular interest are the immunomodulatory effects of peptide agonists of µ-receptors – endomorphins, tetrapeptides, the effects of which are not described in detail in the literature. Due to their structure and properties, endorphins can be considered as potential substitutes for low-molecular-weight opiates.   The aim. To investigate the effect of endorphins-1,2 on the synthesis of oxygen radicals and the absorption activity of innate immunity cells in vitro, in vivo.   Materials and methods. The object of the in vitro study is peripheral venous blood leukocytes from donors aged 22–40 years; the object of the in vivo study is peritoneal flush cells of Swiss white male mice. Oxygen-dependent microbicidal activity was evaluated using a luminol-dependent chemiluminescence reaction. Phagocytic activity was evaluated by flow cytometry.   Results. It has been found that endomorphins inhibited spontaneous production of reactive oxygen species in vitro, in vivo. Endomorphin-2 reduced the intensity of respiratory explosion in stimulated cultures of peritoneal macrophages. Blockade of opiate receptors with naloxone in vitro, in vivo did not cancel the effects of endomorphins. Both peptides and naloxone had no effect on the phagocytic activity of macrophages of the peritoneal cavity of mice in vivo, but in vitro endomorphins led to an increase in the percentage of phagocytosis of peripheral blood leukocytes.   Conclusions. The effects of endomorphins in vitro, in vivo are predominantly depressive.