In the present study, we investigated the effects of progesterone (Pg) on the growth of A3 and its caspase-8-deficient mutant cell line, I9.2, both of which are subclones of a T-cell-derived leukemic Jurkat cell line that lacks the classic cytoplasmic/nuclear Pg receptor. Pg inhibited the cell growth of both cell lines in a dose- and time-dependent manner to a similar extent, regardless of the status of caspase-8 expression. The activation of caspase-9 and -3 was observed in both cell lines following treatment with 50 µM Pg for 24 h. In addition, the activation of caspase-8 was observed in A3 cells. The addition of the pan-caspase inhibitor Boc-D-FMK, significantly suppressed Pg-triggered cytocidal effects in both types of cells. Moreover, exposure to 50 µM Pg for 48 and 72 h resulted in lactate dehydrogenase leakage characteristic of the disruption of cellular membrane integrity. The function of membrane progesterone receptor α coupled directly with the Gi protein was revealed based on the restoration of Pg-triggered loss of mitochondrial membrane potential in the presence of pertussis toxin, an inhibitor specific for Gi protein. These results suggest that growth suppression accompanied with induction of apoptosis by Pg in both Jurkat clone cells was mediated through mitochondrial membrane disruption followed by the activation of the caspase cascade, as a result of the activation of non-genomic effects. The results of the present study provide novel insight into Pg actions toward its use for clinical application in patients with lymphocytic T cell leukemia.

The photoreactions of molecular complexes composed of O 3 and three 5-membered heterocyclic compounds, tetrahydrothiophene (THT), pyrrolidine (PyD), and thiazolidine (TAD), are systematically investigated using matrix-isolation infrared (IR) and UV−visible spectroscopies. Two visible-light absorption bands appear in the visible spectra obtained for O 3 -THT and O 3 -PyD, whereas four bands are observed for O 3 -TAD, which contains both N and S atoms in the heterocyclic ring. Upon visible-light irradiation, O 3 -THT and O 3 -PyD form their corresponding oxide derivatives, tetrahydrothiophene-1-oxide and pyrrolidine-N-oxide. Although two O 3 -TAD complexes with different photoreactivities are detected, both structures form thiazolidine-1-oxide upon combining with O and S atom in the heterocyclic ring, but not thiazolidine-N-oxide. The mechanism of formation of these oxide compounds can be explained by the stability of the oxide compound in the triplet state formed via the combination of O( 3 P) and the paired ring molecule.