Expansion of CD11b⁺Ly6G^high and CD11b⁺CD49d⁺ myeloid cells with suppressive potential in mice with chronic inflammation and light-at-night-induced circadian disruption

Objective: Myeloid-derived suppressor cells (MDSCs) are important negative regulators of immune processes in cancer and other pathological conditions. We suggested that MDSCs play a key role in pathogenesis of chronic inflammation, which precedes and, to a certain extent, induces carcinogenesis. The present study aimed at investigation of MDSCs arising during chronic inflammation and light-at-night (LN)-induced stress, which is shown to accelerate chronic diseases.

Subjects: 67 CD-1 mice and in vitro MDSC cultures.

Treatment: Adjuvant arthritis was induced by a subdermal injection of complete Freund's adjuvant. LN was induced by illumination of 750 lx at night.

Methods: Flow cytometry for evaluation of cell phenotypes and MTT standard test for cell proliferation were used.

Results: Increased levels of splenic CD11b⁺Ly6G^high and CD11b⁺CD49d⁺ myeloid cells possessing suppressive potential in mice with adjuvant arthritis are shown. LN amplifies the process of CD11b⁺Ly6G^high expansion in mice with adjuvant arthritis. Expression of CD62L and CD195 is elevated on the myeloid cells during exposure to LN.

Conclusions: Our study raises the possibility that CD11b⁺Ly6G^high and CD11b⁺CD49d⁺ MDSCs play an important role in the induction of immunosuppressive environment typical for chronic inflammation. Also, LN can affect immune responses during chronic inflammation through recruitment of MDSCs from the bone marrow.