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Updated: Sep 21, 2026
Quantification of Monocyte Chemotactic Activity In Vivo and Characterization of Blood Monocyte Derived Macrophages
Published on: August 12, 2019
Homocysteine mediated expression and secretion of monocyte chemoattractant protein-1 and interleukin-8 in human
Xiaokun Zeng1, Jing Dai, Daniel G Remick
1Institute of Vascular Medicine, Peking University Third Hospital, Beijing, People's Republic of China.
Insights
High homocysteine (Hcy) levels increase monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) secretion. This process involves reactive oxygen species (ROS) and activates pathways like NF-kappaB, suggesting PPARgamma as a therapeutic target.
Area of Science:
- Biochemistry
- Immunology
- Cardiovascular Research
Background:
- Homocysteine (Hcy) is a known risk factor for cardiovascular disease.
- Monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) are key chemokines involved in leukocyte trafficking and are found in atherosclerotic plaques, primarily expressed by macrophages.
Purpose of the Study:
- To investigate if homocysteine induces chemokine secretion from human monocytes.
- To elucidate the underlying mechanisms mediating homocysteine's effects on monocyte chemokine production.
Main Methods:
- Primary human monocytes were cultured and treated with clinically relevant levels of homocysteine.
- Assays were performed to measure protein secretion, mRNA expression, and activity of MCP-1 and IL-8.
- The roles of reactive oxygen species (ROS), NAD(P)H oxidase, protein kinase C, calmodulin, mitogen-activated protein kinases (p38, ERK1/2), nuclear factor-kappaB (NF-kappaB), and peroxisome proliferator-activated receptor gamma (PPARgamma) were examined using specific inhibitors and activators.
Main Results:
- Homocysteine significantly increased MCP-1 and IL-8 protein secretion, mRNA expression, and activity in human monocytes.
- These effects were mediated by homocysteine-induced reactive oxygen species (ROS) production, originating from NAD(P)H oxidase via calmodulin or protein kinase C signaling.
- Inhibition of p38, ERK1/2, NF-kappaB, or activation of PPARgamma significantly reduced homocysteine-induced chemokine secretion.
Conclusions:
- Pathophysiological levels of homocysteine enhance human monocyte function by upregulating MCP-1 and IL-8 via ROS production and subsequent activation of MAPK and NF-kappaB pathways.
- Activation of PPARgamma appears to be sensitive to homocysteine-induced ROS and may serve as a therapeutic target to counteract proatherogenic effects.
Abstract:
Homocysteine (Hcy) is an independent risk factor for cardiovascular disease. Monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) are major chemokines for leukocyte trafficking and have been identified in atheromatous plaques. MCP-1 and IL-8 have been found to express mainly by macrophages in human lesion. We undertook this study to determine whether Hcy could induce the secretion of chemokines from human monocytes and, if so, to explore the mediating mechanism. We found that clinically relevant levels of Hcy (10 to 1000 micromol/L) increased the protein secretion and mRNA expression as well as activity of MCP-1 and IL-8 in cultured primary human monocytes. These effects of Hcy were primarily mediated by reactive oxygen species (ROS) through NAD(P)H oxidase, because Hcy could upregulate the production of ROS and the inhibitors of protein kinase C, calmodulin, free radical scavengers, or NAD(P)H oxidase abolished Hcy-induced ROS production and MCP-1 and IL-8 secretion in these cells. Furthermore, the inhibitors of mitogen-activated protein kinase (p38 and extracellular signal-regulated kinase 1/2) and nuclear factor-kappaB or the activator of peroxisome proliferator-activated receptor gamma (PPARgamma) significantly decreased Hcy-induced MCP-1 and IL-8 secretion in these cells. These data indicate that pathophysiological levels of Hcy can alter human monocyte function by upregulating MCP-1 and IL-8 expression and secretion via enhanced formation of intracellular ROS originated from NAD(P)H oxidase source via calmodulin or protein kinase C signaling pathways and that Hcy-induced ROS subsequently activates mitogen-activated protein kinase (p38 and ERK1/2) and nuclear factor-kappaB in a PPARgamma activator-sensitive manner. Thus, activation of PPARgamma may become a therapeutic target for preventing Hcy-induced proatherogenic effects.
