However, there is no report indicating the correlation between rECP and only TNF a liberation. Trautmann et al. found that IFN g stimulated eosinophil lysate induced bron chial epithelial cells to undergo apoptosis TNF a played an important role in IFN g stimulated eosino phil induced apoptosis in bronchial epithelial cells, as evidenced by TNF a antibody blocking experiment. Besides, previous study showed that co culture with house dust mite activated eosinophils and airway bron chial epithelial cells induced TNF a release. the inhibi tion experiment further indicated that p38 MAPK and NF B were involved in TNF a release in eosinophil AECs system. Since ECP is the major component in eosinophils, it is possible that rECP induced Inhibitors,Modulators,Libraries TNF a production may also involve NF B and MAPK path ways.

Here we hypothesized that up regulated TNF a, triggered by rECP treatment, was released to external environment, where it killed cells via a feedback mechanism. In this way, the death receptor triggered pathway would be stimulated to promote apoptosis. As a result, ECP might be Inhibitors,Modulators,Libraries recognized by cells as portending pathogen invasion, thereby inducing certain immune responses such as cytokine production and apoptosis. In this study, it found that the inactive RNase, mECP, could still induce TNF a production, but highly active RNase A showed no significant TNF a production, strongly suggesting that RNase activity did not corre lated with TNF a production. TNF a receptor activation triggered apoptosis can undergo either mitochondria dependent pathway which is involved in tBid activation and triggers caspase 9 acti vation by releasing cytochrome c, or mitochondria inde pendent pathway.

In our study, caspase 9 inhibitor, MMP assays and cytochrome c release experiments all indicated that rECP did not induce mitochondrial response, hence Inhibitors,Modulators,Libraries the apoptosis underwent mitochondria independent pathway. Previous study has reported that caspase 6 is able to activate caspase 8 and involved in mitochondrial response. However, it was proved that ECP induced apoptosis did not require mitochon Inhibitors,Modulators,Libraries drial response. hence we speculated that caspase 8 was activated by TNFR pathway instead of caspase Inhibitors,Modulators,Libraries 6. Taken together, Figure 8 presents that ECP induces apoptosis involved in TNF a related caspase 8 activation through mitochondria independent pathway. Although ECP belongs to the pancreatic type RNase family, its RNase activity is relatively weak.

More over, the RNase activity of ECP is not essential for its cytotoxicity. ECP, EDN, and RNase A all belong to the pancreatic RNase family, and their RNase activities can be detected. As illu strated in our additional file 5, ECP and mutant rECP H15A K38I H128A with low or no RNase activity have higher selleck chem inhibitor toxicity toward BEAS 2B cells, whereas EDN and RNase A with high RNase activity show no toxicity toward BEAS 2B cells.