[Peroxisome proliferation-activated receptor-gamma ligands ameliorate autoimmune myocarditis associated with inhibition of T cell immunity].

OBJECTIVE

To investigate the role of peroxisome proliferator-activated receptor-gamma (PPAR gamma) on autoimmune myocarditis, and to test the hypothesis that PPAR-gamma ligands reduce experimental autoimmune myocarditis (EAM) associated with inhibition of the expansion and activation of self-sensitive T cells.

METHODS

EAM was induced in Lewis rats by immunization with porcine cardiac myosin. Then the rats were divided into 3 groups of 9 rats: PPAR-gamma ligand 15-deoxy-(12,14)-PGJ(2) (15d-PGJ(2)) group (15d-PGJ(2) was injected intraperitoneally at the dosage of 200 microg.kg(-1).d(-1)), pioglitazone (PIO) group (PIO was mixed with the food and than fed at the dosage of 10 mg.kg(-1).d(-1)), and positive control group (phosphate-buffered saline was injected intraperitoneally). Nine normal rats were used as normal controls. Three weeks later, the rats underwent thoracotomy to undergo pathologic examination. The numbers of CD4(+) cells, CD8(+) cells, and macrophages were calculated by microscopy. Immunohistochemistry was used to examine the location and expression of PPAR gamma. Western blotting was used to examine the relative amount of PPAR gamma protein. The proliferative response and the cytotoxicity of T cell-enriched splenocytes and lymph node cells were determined. Another rats were killed 12 days after immunization. Their spleens and lymph nodes were taken out. T-cell rich splenocytes and cells from the lymph nodes were cultured. Cardiac myosin and 15d-PGJ(2) were added. [(3)H] thymine was added 72 hours after. ELISA was used to examine the interferon-gamma (IFN-gamma) in the supernatant. 15d-PGJ(2), PIO, or PBS were given to immunize the rats. The rats were killed 12 days after. The lymph nodes were taken out to make single cell suspension. (51)Cr was used to label the cells so as to calculate the %cytotoxicity.

RESULTS

All immunized rats showed myocarditis. The numbers of CD4(+) cells, CD8(+) T cells, and macrophages, were 18 +/- 5, 7 +/- 2, and 45 +/- 8/six 0.25 mm x 0.25 mm squares. PPAR gamma was mainly located in the nuclear and perinuclear regions of infiltrating inflammatory cells, such as mononuclear cells and macrophage-like cells. The expression of PPAR gamma in the myocardium of EAM rats was 3.7 times higher than of the normal rats. The heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores of the 15d-PGJ group were significantly lower than those of the positive control group. The numbers of CD4(+) cells of the 15d-PGJ and PIO groups were 8 +/- 2 and 10 +/- 3, both significantly lower than that of the positive control group (both P < 0.01), the numbers of CD8(+) cells of the 15d-PGJ and PIO groups were 3 +/- 1 and 4 +/- 2 respectively, both significantly lower than that of the positive control group (P < 0.01 and P < 0.05), and the numbers of macrophages of the 15d-PGJ and PIO groups were 22 +/- 4 and 26 +/- 6 respectively, both significantly lower than that of the positive control group (both P < 0.01). The myocardiogenicity and the severity of myocarditis of the 15d-PGJ(2)- and PIO-groups were at lower degrees compared with those of the positive control group. The % cytotoxic activity was 10.2% +/- 2.6% in the 15d-PGJ(2) group and was 11.6% +/- 3.7% in the PIO group, both significantly lower than that of the positive control group (37.7% +/- 8.4%, both P < 0.01) Stimulated by cardiac myosin, the T-cell rich splenocytes and cells from lymph nodes showed obvious proliferation and production of IFN-gamma. The cardiac myosin-stimulated cell proliferation and production of IFN-gamma in the 15d-PGJ(2) and PIO groups were significantly reduced in comparison with those in the positive control group.

CONCLUSION

PPAR-gamma ligands ameliorate EAM associated with inhibition of expansion and activation of the self-sensitive T cells.