Effect of cyclosporin A intervention on the immunological mechanisms of coronary heart disease and restenosis

Macrophage lipid accumulation in the presence of immunosuppressive drugs mycophenolate mofetil and cyclosporin A

OBJECTIVE

Mycophenolate (MPA) and cyclosporin A (CsA) are two immunosuppressive agents currently used for the treatment of autoimmune diseases. However, reports regarding their effects on inflammation and lipid handling are controversial. Here, we compare the effect of these two drugs on the expression of proteins involved in cholesterol handling and lipid accumulation in a macrophage cell system utilizing M0, M1 and M2 human macrophages and in murine bone marrow-derived macrophages (BMDM).

METHODS

Differentiated M0, M1 and M2 subsets of THP-1 human macrophages were subjected to various concentrations of either MPA or CsA. Expression of proteins involved in reverse cholesterol transport (ABCA1 and 27-hydroxylase) and scavenger receptors, responsible for uptake of modified lipids (CD36, ScR-A1, CXCL16 and LOX-1), were evaluated by real-time PCR and confirmed with Western blot. DiI-oxidized LDL internalization assay was used to assess foam cell formation. The influence of MPA was also evaluated in BMDM obtained from atherosclerosis-prone transgenic mice, ApoE^-/- and ApoE^-/-Fas^-/-.

RESULTS

In M0 macrophages, MPA increased expression of ABCA1 and CXCL16 in a concentration-dependent manner. In M1 THP-1 macrophages, MPA caused a significant increase of 27-hydroxylase mRNA and CD36 and SR-A1 receptor mRNAs. Exposure of M2 macrophages to MPA also stimulated expression of 27-hydroxylase, while downregulating all evaluated scavenger receptors. In contrast, CsA had no impact on cholesterol efflux in M0 and M1 macrophages, but significantly augmented expression of ABCA1 and 27-hydroxylase in M2 macrophages. CsA significantly increased expression of the LOX1 receptor in naïve macrophages, downregulated expression of CD36 and SR-A1 in the M1 subpopulation and upregulated expression of all evaluated scavenger receptors. However, CsA enhanced foam cell transformation in M0 and M2 macrophages, while MPA had no effect on foam cell formation unless used at a high concentration in the M2 subtype.

CONCLUSIONS

Our results clearly underline the importance of further evaluation of the effects of these drugs when used in atherosclerosis-prone patients with autoimmune or renal disease.

Inhibition of peptidyl-prolyl cis-trans isomerase B mediates cyclosporin A-induced apoptosis of islet β cells

Cyclosporin A (CsA) is widely used as an immunosuppressor in the context of organ transplantation or autoimmune disorders. Recent studies have revealed the detrimental effects of CsA on insulin resistance and pancreatic β cell failure; however, the molecular mechanisms are unknown. The present study sought to confirm the associations between CsA and β cell failure, and to investigate the roles of proinsulin folding and endoplasmic reticulum (ER) stress in CsA-induced β cell failure. The viability of MIN6 cells treated with CsA was evaluated with MTT assay. Expression levels of insulin, peptidyl-prolyl cis-trans isomerase B (PPIB), cleaved caspase-3, phospho-protein kinase R (PKR)-like endoplasmic reticulum kinase (p-PERK), PKR-like endoplasmic reticulum kinase (PERK), binding immunoglobulin protein (BIP), and C/EBP homologous protein (CHOP) were detected via reducing western blot assay. Non-reducing western blot analysis was performed to examine the expression of misfolded proinsulin peptides. The proliferation of MIN6 cells was not inhibited by CsA at concentrations <1 µmol/l. CsA treatment resulted in the decreased expression of insulin and PPIB; however, it also increased the phosphorylation of PERK, and upregulated the expression of PERK, BIP, CHOP and cleaved caspase-3. The results indicated that CsA could induce pancreatic β cell dysfunction and the potential mechanism underlying this phenomenon may be PPIB-associated proinsulin misfolding, which in turn induces ER stress in β cells.