Anti-Apoptotic Effect of Synthetic Leu-Enkephalin Dalargin on Rat Leukocytes in Cold Stress Model in Vivo

Ivan Shcheniavsky

doi:10.15407/cryo31.01.003

Abstract

In this research, a protective effect of synthetic analogue of leu-enkephalin dalargin on peripheral blood leukocytes of cold stress-exposed homeotherms has been investigated. The impact of this peptide and in vivo cold stress on cell composition of leukoconcentrate, leukocyte viability and DNA fragmentation degree in rat leukocytes, has been studied by using confocal microscopy. A decreased relative count of lymphocytes and an increased neutrophil one were established as significantly less pronounced in the animals injected with dalargin before cooling, than in non-handled ones. The dalargin administration was also shown to enhance the viability of peripheral blood leukocytes in rats exposed to cold stress. Preliminary administration of dalargin to animals significantly reduced both the degree of DNA fragmentation and a relative count of leukocytes with fragmented DNA in peripheral blood. Simultaneous introduction of opioid receptor antagonist naloxone to animals eliminated a protective effect of opioid receptor agonist dalargin. Our findings demonstrated the opioid receptor-mediated antiapoptotic effect of dalargin on peripheral blood leukocytes under in vivo cold stress.

Highlights

In this research, a protective effect of synthetic analogue of leu-enkephalin dalargin on peripheral blood leukocytes of cold stress-exposed homeotherms, has been investigated
The ratio of lymphocyte subpopulations in spleen, lymph nodes and thymus was established to change in animals under stress conditions [28], as a result the relative count of cytotoxic T-killers (CD8+), as well as natural killers increased
The relative count of lymphocytes was 59–71.5%, and for neutrophils it made 11.7–28.8%. This almost threefold predominance of lymphocytes over neutrophilic granulocytes in blood is specific for animals of this species [23]

Summary

Introduction

A protective effect of synthetic analogue of leu-enkephalin dalargin on peripheral blood leukocytes of cold stress-exposed homeotherms, has been investigated. Many recent studies have shown some substances of peptide origin, obtained from tissues of hibernating or cold-adapted species, to be able to enhancing the resistance to body temperature decrease in homeotherms [18, 21, 33]. Such neuropeptides as leu- and met-enkephalins, as well as β-endorphins are mainly involved into the regulation of hibernation [3, 6, 27].

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