Cyclophilin A enhances macrophage differentiation and lipid uptake in high glucose conditions: a cellular mechanism for accelerated macro vascular disease in diabetes mellitus.

Surya Ramachandran,Anandan Vinitha,Cheranellore Chandrasekharan Kartha

doi:10.1186/s12933-016-0467-5

Surya Ramachandran, Anandan Vinitha + Show 1 more

Open Access

https://doi.org/10.1186/s12933-016-0467-5

Copy DOI

Abstract

BackgroundVascular disease in diabetes is initiated by monocyte adhesion to vascular endothelium, transmigration and formation of foam cells. Increasing clinical evidence supports a role for the secretory protein, cyclophilin A in diabetic vascular disease. The means by which cyclophilin A contributes to vascular lesion development in diabetes is however largely unknown.MethodsIn this study we investigated using THP1 cells and human monocytes whether cyclophilin A under hyperglycemic conditions, functions in the inflammatory cascade as a chemoattractant and increases lipid uptake by formation of foam cells invitro. We developed an invitro model of monocytes cultured in 20 mm glucose (high glucose) equivalent to 360 mg/dL of plasma glucose levels. These monocytes were then differentiated into macrophages using PMA and subsequently transformed to lipid laden foam cells using oxidized low density lipoproteins in the presence and absence of cyclophilin A. This cellular model was used to study monocyte to macrophage differentiation, transmigration and foam cell formation. A similar cellular model using siRNA mediated transient elimination of the cyclophilin A gene as well as chemical inhibitors were used to further confirm the role of cyclophilin A in the differentiation and foam cell formation process.ResultsCyclophilin A effectively increased migration of high glucose treated monocytes to the endothelial cell monolayer (p < 0.0001). In the presence of cyclophilin A, differentiated macrophages, when treated with oxLDL had a 36 percent increase in intracellular lipid accumulation (p = 0.01) when compared to cells treated with oxLDL alone. An increased flux of reactive oxygen species was also observed (p = 0.01). Inflammatory cytokines such as TNF-α, MCP-1 and cyclophilin A were significantly increased. Silencing cyclophilin A in THP-1 cells and human monocytes using siRNA or chemical inhibitor, TMN355 resulted in decrease in lipid uptake by 65–75% even after exposure to oxidized LDL. The expression of scavenger receptors expressed during differentiation process, CD36 and LOX-1 were decreased (p < 0.0001). Levels of extracellular cyclophilin A and other inflammatory cytokines such as TNF-α and MCP-1also significantly reduced.ConclusionsTaken together, we describe here a possible cellular basis by which cyclophilin A may accelerate atherogenesis in diabetes mellitus.Electronic supplementary materialThe online version of this article (doi:10.1186/s12933-016-0467-5) contains supplementary material, which is available to authorized users.

Highlights

Vascular disease in diabetes is initiated by monocyte adhesion to vascular endothelium, transmigration and formation of foam cells
Cyclophilin A increases monocyte adhesion and transmigration into the endothelium under high glucose conditions The inflammation cascade begins with adhesion of monocytes to the endothelial cells and transmigration into the intima
The pictures of filter stained with Giemsa reveals increase in number of cells that have adhered to the filter on treatment with high glucose and cyclophilin A (Fig. 1b)

Summary

Introduction

Vascular disease in diabetes is initiated by monocyte adhesion to vascular endothelium, transmigration and formation of foam cells. Monocytes adhere to endothelial cells and later migrate into the subendothelial space in response to chemotactic activation These monocytes differentiate into macrophages and take up oxidized lipids. High blood glucose levels further facilitate monocyte adhesion to endothelial cells, differentiation of monocyte into macrophages promoting atherogenesis [1], increasing the risk of vascular disease in diabetes mellitus. In an earlier study we found that high glucose activates monocytes to secrete proteins which may increase the risk for vascular lesion formation [2] One such protein is cyclophilin A, an immunophilin which has been discovered to be elevated in the blood of patients with type 2 diabetes as well as patients with coronary artery disease [3, 4]

Objectives

Methods

Results

Conclusion