Thiol Oxidative Stress Induced by Metabolic Disorders Amplifies Macrophage Chemotactic Responses and Accelerates Atherogenesis and Kidney Injury in LDL Receptor-Deficient Mice

Abstract

Background-Strengthening the macrophage glutathione redox buffer reduces macrophage content and decreases the severity of atherosclerotic lesions in LDL receptor-deficient (LDLR Ϫ/Ϫ ) mice, but the underlying mechanisms were not clear. This study examined the effect of metabolic stress on the thiol redox state, chemotactic activity in vivo, and the recruitment of macrophages into atherosclerotic lesions and kidneys of LDL-R Ϫ/Ϫ mice in response to mild, moderate, and severe metabolic stress. Methods and Results-Reduced glutathione (GSH) and glutathione disulfide (GSSG) levels in peritoneal macrophages isolated from mildly, moderately, and severe metabolically-stressed LDL-R Ϫ/Ϫ mice were measured by HPLC, and the glutathione reduction potential (E h ) was calculated. Macrophage E h correlated with the macrophage content in both atherosclerotic (r 2 ϭ0.346, Pϭ0.004) and renal lesions (r 2 ϭ0.480, Pϭ0.001) in these mice as well as the extent of both atherosclerosis (r 2 ϭ0.414, Pϭ0.001) and kidney injury (r 2 ϭ0.480, Pϭ0.001). Compared to LDL-R Ϫ/Ϫ mice exposed to mild metabolic stress, macrophage recruitment into MCP-1-loaded Matrigel plugs injected into LDL-R Ϫ/Ϫ mice increased 2.6-fold in moderately metabolically-stressed mice and 9.8-fold in severely metabolically-stressed mice. The macrophage E h was a strong predictor of macrophage chemotaxis (r 2 ϭ0.554, PϽ0.001). Conclusion-Thiol oxidative stress enhances macrophage recruitment into vascular and renal lesions by increasing the responsiveness of macrophages to chemoattractants. This novel mechanism contributes at least in part to accelerated atherosclerosis and kidney injury associated with dyslipidemia and diabetes in mice. Key Words: glutathione Ⅲ macrophage recruitment Ⅲ metabolic stress Ⅲ atherosclerosis Ⅲ inflammation M etabolic disorders such as hypercholesterolemia and diabetes are strongly associated with both macro-and microvascular diseases, a common feature of which is the recruitment of blood monocyte-derived macrophages to sites of vascular injury. Whereas most studies exploring the mechanisms underlying atherosclerosis and other vascular pathologies have focused on the impact of a dysregulated metabolism on the vasculature itself, a number of more recent studies suggest that metabolic disorders may also directly impact monocytes and alter their functionalities in ways that promote and accelerate the disease process. Phenotypic abnormalities in blood monocytes of diabetic patients have been reported, including altered metabolism, 1-3 phagocytosis, 4,5 and cytokine release. 6 -8 Furthermore, peritoneal macrophages isolated from either atherosclerosis-prone mice or diabetic mice show altered cytokine and chemokine responses compared with macrophages from healthy control mice. 9,10 However, it is not yet well-understood to what extent monocyte dysfunction induced by metabolic diseases contributes to macrophage recruitment and vascular diseases such as atherosclerosis.The recruitment of blood monocyte-derived macrophages into the vessel wall is co...

Redox regulation of MAPK phosphatase 1 controls monocyte migration and macrophage recruitment

“…MKPs are sensitive to inactivation via the reversible oxidation of their active-site cysteine (32). We showed that in monocytes metabolic stress promotes protein S-glutathionylation, i.e., the formation of mixed disulfides between GSH and reactive protein thiols (17,18); however, Sglutathionylation of MKPs had not been reported. To identify the mechanism by which metabolic stress promotes the inactivation and loss of MKP-1 in monocytes and to explore whether MKP-1 is S-glutathionylated in metabolically primed monocytes, we preloaded THP-1 monocytes with biotin-labeled glutathione and performed streptavidin-bead pulldown experiments.…”

“…In atherosclerosis-prone LDL-Real (LDL-R)-null mice, moderate metabolic stress primes blood monocytes and increases their responsiveness to MCP-1-induced recruitment, a phenotypic transformation that is enhanced dramatically if these mice are rendered diabetic (18). Diabetic conditions accelerated the formation of atherosclerotic lesions (18) and were associated with the partial loss of MKP-1 activity in blood monocytes (Fig.…”

“…We induced moderate metabolic stress by feeding the transplant-recipient mice a high-fat diet for 10 wk. Three days before the animals were killed, we assessed monocyte chemotaxis and recruitment in each mouse by implanting s.c. MCP-1-loaded Matrigel plugs (18). As depicted in Fig.…”

“…In dyslipidemic and in diabetic mice the increased responsiveness of monocytes to chemokine-induced migration correlated with the level of intracellular thiol oxidative stress and was a strong predictor of both lesion size and macrophage content of atherosclerotic plaques (17,18). Monocyte priming by metabolic stress is mediated by the induction of Nox4, an NADPH oxidase recently identified in monocytes and macrophages (19).…”

“…Our recent studies explored this possibility, and we showed that metabolic stress primes monocytes for activation by chemoattractants, including monocyte chemoattractant protein-1 (MCP-1, also known as "CCL2," "SCYA2," and "MCAF"), a major chemoattractant involved in the recruitment of macrophages into atherosclerotic lesions (14)(15)(16), transforming these cells into a hypermigratory, proinflammatory phenotype (17,18). In dyslipidemic and in diabetic mice the increased responsiveness of monocytes to chemokine-induced migration correlated with the level of intracellular thiol oxidative stress and was a strong predictor of both lesion size and macrophage content of atherosclerotic plaques (17,18).…”