RESUMO
Early studies with first-generation poly (ADP-ribose) polymerase (PARP) inhibitors have already indicated some therapeutic potential for sulfur mustard (SM) injuries. The available novel and more potential PARP inhibitors, which are undergoing clinical trials as drugs for cancer treatment, bring it back to the centre of interest. However, the role of PARP-1 in SM-induced injury is not fully understood. In this study, we selected a high potent specific PARP inhibitor ABT-888 as an example to investigate the effect of PARP inhibitor in SM injury. The results showed that in both the mouse ear vesicant model (MEVM) and HaCaT cell model, PARP inhibitor ABT-888 can reduce cell damage induced by severe SM injury. ABT-888 significantly reduced SM induced edema and epidermal necrosis in MEVM. In the HaCaT cell model, ABT-888 can reduce SM-induced NAD(+)/ATP depletion and apoptosis/necrosis. Then, we studied the mechanism of PARP-1 in SM injury by knockdown of PARP-1 in HaCaT cells. Knockdown of PARP-1 protected cell viability and downregulated the apoptosis checkpoints, including p-JNK, p-p53, Caspase 9, Caspase 8, c-PARP and Caspase 3 following SM-induced injury. Furthermore, the activation of AKT can inhibit autophagy via the regulation of mTOR. Our results showed that SM exposure could significantly inhibit the activation of Akt/mTOR pathway. Knockdown of PARP-1 reversed the SM-induced suppression of the Akt/mTOR pathway. In summary, the results of our study indicated that the protective effects of downregulation of PARP-1 in SM injury may be due to the regulation of apoptosis, necrosis, energy crisis and autophagy. However, it should be noticed that PARP inhibitor ABT-888 further enhanced the phosphorylation of H2AX (S139) after SM exposure, which indicated that we should be very careful in the application of PARP inhibitors in SM injury treatment because of the enhancement of DNA damage.
RESUMO
BACKGROUND: In clinical studies, the findings on sulfur mustard (SM) toxicity for CD3(+)CD4(+) and CD3(+)CD8(+) T lymphocyte subsets are contradictory. In animal experiments, the effect of SM on the T cell number and proliferation is incompatible and is even the opposite of the results in human studies. In this study, we observed the dynamic changes of T lymphocytes in the first week in a high-dose SM-induced model. METHODS: Mice were exposed to SM by subcutaneous injection (20 mg/kg) and were sacrificed 4 h, 24 h, 72 h and 168 h later. Spleen T lymphocyte proliferation was evaluated by (3)H-TdR. Flow cytometric analysis was used to observe the percentage of CD3(+)CD4(+) and CD3(+)CD8(+) T lymphocyte subsets. The IL-1ß, IL-6, IL-10 and TNF-α levels in plasma were assayed using the Luminex method. DNA damage in bone marrow cells was observed with the single cell gel electrophoresis technique (SCGE). RESULTS: SM continuously inhibited the proliferation of lymphocytes for 7 days, and there was a significant rebound of Con A-induced T lymphocyte proliferation only at 24 h. The percentage of CD3(+)CD4(+) and CD3(+)CD8(+) lymphocytes was upregulated, which was accompanied by increased IL-1ß and TNF-α and decreased IL-10. The IL-6 level was gradually decreased in the PG group at 4 h. The peak of lymphocytic apoptosis and DNA damage occurred at 24 h and 72 h, respectively. CONCLUSION: Our results show that SM significantly inhibited T lymphocyte proliferation as well as induced CD3(+)CD4(+) and CD3(+)CD8(+) upregulation. SM intoxication also significantly increased the levels of pro-inflammatory cytokines (IL-1ß, IL-6 and TNF-α) and inhibited the level of anti-inflammatory cytokine IL-10. Our results may partly be due to the significant SM induced significant apoptosis and necrosis of lymphocytes as well as DNA damage of bone marrow cells. The results provided a favorable evaluation of SM immune toxicity in an animal model.
