Melanocortin 1 Receptor Deficiency in Hematopoietic Cells Promotes the Expansion of Inflammatory Leukocytes in Atherosclerotic Mice

Abstract

Melanocortin receptor 1 (MC1-R) is expressed in leukocytes, where it mediates anti-inflammatory actions. We have previously observed that global deficiency of MC1-R signaling perturbs cholesterol homeostasis, increases arterial leukocyte accumulation and accelerates atherosclerosis in apolipoprotein E knockout (Apoe-/-) mice. Since various cell types besides leukocytes express MC1-R, we aimed at investigating the specific contribution of leukocyte MC1-R to the development of atherosclerosis. For this purpose, male Apoe-/- mice were irradiated, received bone marrow from either female Apoe-/- mice or MC1-R deficient Apoe-/- mice (Apoe-/- Mc1re/e) and were analyzed for tissue leukocyte profiles and atherosclerotic plaque phenotype. Hematopoietic MC1-R deficiency significantly elevated total leukocyte counts in the blood, bone marrow and spleen, an effect that was amplified by feeding mice a cholesterol-rich diet. The increased leukocyte counts were largely attributable to expanded lymphocyte populations, particularly CD4+ T cells. Furthermore, the number of monocytes was elevated in Apoe-/- Mc1re/e chimeric mice and it paralleled an increase in hematopoietic stem cell count in the bone marrow. Despite robust leukocytosis, atherosclerotic plaque size and composition as well as arterial leukocyte counts were unaffected by MC1-R deficiency. To address this discrepancy, we performed an in vivo homing assay and found that MC1-R deficient CD4+ T cells and monocytes were preferentially entering the spleen rather than homing in peri-aortic lymph nodes. This was mechanistically associated with compromised chemokine receptor 5 (CCR5)-dependent migration of CD4+ T cells and a defect in the recycling capacity of CCR5. Finally, our data demonstrate for the first time that CD4+ T cells also express MC1-R. In conclusion, MC1-R regulates hematopoietic stem cell proliferation and tissue leukocyte counts but its deficiency in leukocytes impairs cell migration via a CCR5-dependent mechanism.

The effect of acute exercise on circulating immune cells in newly diagnosed breast cancer patients

“…After centrifugation, the cells were resuspended in 300 µL of PBS and samples were pipetted into a flat bottom 96-well plate. As applied previously 34 , 48 – 52 , samples were analyzed by running 150 µL of each sample with a BD LSR Fortessa™ flow cytometer (BD Biosciences, San Jose, USA) on the same day using BD FACSDiVa v.8 program (BD Biosciences, San Jose, USA). All samples were analyzed by the same person under the same conditions.…”

α-Melanocyte-stimulating hormone alleviates pathological cardiac remodeling via melanocortin 5 receptor

“…Heart samples were first homogenized in QIAzol Lysis Reagent using the Qiagen TissueLyser LT Bead Mill (QIAGEN, Venlo, Netherlands) and total RNA was thereafter extracted using Direct-zol RNA Miniprep. RNA was reverse-transcribed to cDNA (PrimeScript RT reagent kit, Takara Clontech) and quantitative real-time polymerase chain reaction (RT-PCR) was performed with SYBR Green protocols (Kapa Biosystems, MA, USA) and a real-time PCR detection system (Applied Biosystems 7300 Real-Time PCR system) (Rinne et al, 2017 ; Kadiri et al, 2021 ). Target gene expression was normalized to a housekeeping gene (ribosomal protein S18; RPS18, glyceraldehyde-3-phosphate dehydrogenase; GAPDH or β-actin; ACTB) using the comparative ΔCt method and results are presented as relative transcript levels (2 -ΔΔCt ).…”

Acute exercise mobilizes CD8+ cytotoxic T cells and NK cells in lymphoma patients

“…After centrifugation, the cells were resuspended in 300 µL of PBS and samples were pipetted into a flat bottom 96-well plate. As applied previously ( Rinne et al, 2018 ; Viitala et al, 2019 ; Kadiri et al, 2020 ; Kadiri et al, 2021 ; Tadayon et al, 2021 ), samples were analyzed by running 150 µL of each sample with a BD LSR Fortessa™ flow cytometer (BD Biosciences, San Jose, United States) on the same day using BD FACSDiVa v.8 program (BD Biosciences, San Jose, United States). All samples were analyzed by the same person under the same conditions.…”