Moreover, the amount of inclusion carrying cells decreases from 48 hpi to 72 hpi when a small initial infec tious dose was used. However, further investigations need either to be done to Inhibitors,Modulators,Libraries prove an actual release mechanism. The question remains open what the molecular factors are that lead to release of bacteria and cell death. Signals leading to cell death could be Inhibitors,Modulators,Libraries the contact of Chlamydia with pro teins in the cytoplasm. Although metabolically active Chlamydia are released from inclusions, current data do not allow to determine whether it is the contact of RBs or and EBs with the cytoplasm. Another possibility could be that chlamydial proteins that are released along with the pathogens during inclusion rupture induce cell death. A membrane lysing substance targeting preferentially eukaryotic membranes could induce permeabilization in major membranous structures.

The nature of such pro teins putatively involved in cell death induction remains to be elucidated. Moreover, treatment of Chlamydia infected cells with chlo ramphenicol completely Inhibitors,Modulators,Libraries abolished cell death induction. This indicates that the initial bacterial burden can be excluded as an initiator Inhibitors,Modulators,Libraries of aponecrosis. Although chlamydial induction of apoptosis was described in some studies strikingly low numbers of single TUNEL positive cells were observed throughout the infection cycle in our experiments, a reflection of sponta neous apoptosis of residual uninfected cells within the infected population. It is evident that Chlamydia can influ ence cell death in order to successfully end the replication cycle.

However, it is also evident that the nature of induced cell death is more intricate than a sole activation of the apoptotic pathway. Depending on different cell types, chlamydial strains and experimental apoptotic pro cedures, a combination between apoptosis and necrosis in a cell population and aponecrosis Inhibitors,Modulators,Libraries at the single cell level have been described. In this study, infected dead HAEC displayed apoptotic features such as condensation of the chromatin together with necrotic fea tures, including early damage to organelles and disruption of the cell membrane. This morphology was previously observed also in other cells and was termed aponecrosis. Additionally, we show that cell death mor phology does not differ between Ganetespib solubility cells infected with high infection doses for a short period of time and cells sub jected to low infection doses for longer time. We never observed dead HAEC containing inclusions, which is in accordance with previous studies showing that Chlamydia possesses both pro and anti apoptotic capabil ities. Chlamydia inhibits apoptosis by blocking the release of cytochrome c through the interaction with pro apoptotic agents such as BH3 only proteins and Bax Bak.