Apoptosis and the expression of caspase-1, 3, 8, IFN-gamma, and iNOS mRNA in Leprosy Lesions

Choi, Yoon Jeong; Kim, Myung Hwa; Choi, Hae Young; Myung, Ki Bum

Abstract

Apoptosis is an unique physiologic process of programmed cell death, playing an important role in the development and homeostasis of both normal and pathologic tissues. In mycobacterial infections, apoptosis of the macrophage is an important defense mechanism, which prevents the spread of the infection. The purpose of this study is to investigate whether apoptosis occurs in leprosy, and whether a positive correlation occurs among caspase-1, 3, 8, IFN-gamma, and iNOS among normal tissue, BT, and LL lesions. TUNEL staining and double immunohistochemical staining with anti-CD8, CD68 antibodies were done in paraffin-embedded tissue sections of 10 cases of paucibacillary leprosy and 8 cases of multibacillary leprosy. The mRNA expression of caspase-1, 3, 8, IFN-gamma, and iNOS was detected by RT-PCR analysis. The results are summarized as follows: 1. The number of apoptotic cells was 3.5+/-1.6 in paucibacillary leprosy and 6.1+/-3.7 in multibacillary leprosy. The difference was statistically insignificant. 2. Caspase-1 mRNA was expressed in order of LL, BT, and normal skin, and the differences were statistically insignificant. 3. Caspase-3 mRNA was expressed in order of LL, BT, and normal skin. Between LL and normal skin, the difference was statistically significant. 4. Caspase-8 mRNA was expressed in order of LL, normal skin, and BT, and differences were statistically significant. Especially, between LL and BT, the difference was statistically significant. 5. IFN-gamma mRNA was expressed in order of LL, BT, and normal skin. Between LL and normal skin, the difference was statistically significant. 6. iNOS mRNA was expressed in order of LL, BT, and normal skin. Between LL and normal skin, the difference was statistically significant. 7. Statistically significant positive correlation between caspase-1 and IFN-gamma, caspase-3 and iNOS, and caspase-8 and iNOS was found in normal tissue, BT, and LL. Statistically significant positive correlation between caspase-1 and IFN-gamma was shown in BT and LL. In conclusion, apoptosis exists in leprosy lesions and apoptotic cells expressing CD8 and CD68 positivity. Number of apoptotic cells in multibacillary leprosy lesions was insignificantly more than that of paucibacillary lesions. Agents inducing apoptosis such as caspase-3, caspase-8, IFN-gamma, and iNOS significantly increased in leprosy lesions, especially in LL lesions comparing to normal tissues. Apoptosis in the LL lesions might rather be an additive result to macrophage activation than play a defense role. Only the mRNA expression of caspase-8 significantly increased in LL lesions more than in BT lesions. So caspase-8 might be a major player of the apoptotic pathway in LL.