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Lipopolysaccharide increases monocyte binding to mesangial cells through fractalkine and its receptor
1Department of Bioinspired Science and Division of Life and Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Korea.
Abstract:
Fractalkine (CX3CL1) is a unique chemokine that functions not only as a chemokine but also as an adhesion molecule. Fractalkine plays an important role in the recruitment of macrophages into the kidneys by binding to its specific receptor CX3CR1, and renal fractalkine expression was shown to be increased in chronic renal allograft rejection. Considering that microcapillary inflammation is a key feature of chronic renal allograft rejection, the present study examined whether monocytes bind to mesangial cells cultured in the presence of lipopolysaccharide (LPS) through fractalkine/CX3CR1 in order to understand their regulation with respect to inflammation-induced renal allograft dysfunction. Mouse mesangial cells were stimulated with LPS in the presence or absence of fractalkine or CX3CR1 siRNA. Calcein-AM-labeled monocytes were used to evaluate monocyte binding. Fractalkine and CX3CR1 mRNA and protein expression were measured by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. LPS at 100 ng/mL significantly increased monocyte binding to mesangial cells. Each siRNA against fractalkine or CX3CR1 effectively inhibited LPS-induced monocyte-mesangial cell binding. Fractalkine and CX3CR1 mRNA expression were enhanced in mesangial cells stimulated with LPS. Fractalkine protein synthesis in media and lysate of mesangial cells were also induced by LPS. These results demonstrated that LPS induces monocyte-mesangial cell binding through the fractalkine/CX3CR1 system and suggested that fractalkine/CX3CR1 system may contribute to renal inflammation leading to chronic renal allograft rejection.
Insights
Lipopolysaccharide (LPS) increases monocyte binding to kidney mesangial cells via the fractalkine/CX3CR1 pathway. This interaction is crucial for understanding inflammation in renal allograft dysfunction and rejection.
Area of Science:
- Immunology
- Nephrology
- Cell Biology
Background:
- Fractalkine (CX3CL1) is a dual-function chemokine and adhesion molecule vital for immune cell trafficking.
- Increased renal fractalkine expression correlates with chronic renal allograft rejection, a process marked by microcapillary inflammation.
Purpose of the Study:
- To investigate the role of the fractalkine/CX3CR1 axis in lipopolysaccharide (LPS)-induced monocyte binding to mesangial cells.
- To elucidate the regulation of this system in the context of inflammation-driven renal allograft dysfunction.
Main Methods:
- Mouse mesangial cells were stimulated with LPS, with or without fractalkine or CX3CR1 siRNA.
- Monocyte binding was quantified using Calcein-AM-labeled monocytes.
- Gene and protein expression of fractalkine and CX3CR1 were analyzed via qPCR and ELISA.
Main Results:
- LPS significantly enhanced monocyte binding to mesangial cells.
- siRNA targeting fractalkine or CX3CR1 effectively blocked LPS-induced binding.
- LPS upregulated both mRNA and protein expression of fractalkine and CX3CR1 in mesangial cells.
Conclusions:
- LPS induces monocyte-mesangial cell adhesion through the fractalkine/CX3CR1 signaling pathway.
- The fractalkine/CX3CR1 system is implicated in renal inflammation, potentially contributing to chronic renal allograft rejection.
