The IKK inhibitor BMS-345541 affects multiple mitotic cell cycle transitions

The IkappaB kinase (IKK) complex controls processes such as inflammation, immune responses, cell survival and the proliferation of both normal and tumor cells. By activating NFkappaB, the IKK complex contributes to G1/S transition and first evidence has been presented that IKKalpha also regulates entry into mitosis. At what stage IKK is required and whether IKK also contributes to progression through mitosis and cytokinesis, however, has not yet been determined. In this study, we use BMS-345541, a potent allosteric small molecule inhibitor of IKK, to inhibit IKK specifically during G2 and during mitosis. We show that BMS-345541 affects several mitotic cell cycle transitions, including mitotic entry, prometaphase to anaphase progression and cytokinesis. Adding BMS-345541 to the cells released from arrest in S-phase blocked the activation of Aurora A, B and C, Cdk1 activation and histone H3 phosphorylation. Additionally, treatment of the mitotic cells with BMS-345541 resulted in precocious cyclin B1 and securin degradation, defective chromosome separation and improper cytokinesis. BMS-345541 was also found to override the spindle checkpoint in nocodazole-arrested cells. In vitro kinase assays using BMS-345541 indicate that these effects are not primarily due to a direct inhibitory effect of BMS-345541 on mitotic kinases such as Cdk1, Aurora A or B, Plk1 or NEK2. This study points towards a new potential role of IKK in cell cycle progression. Since deregulation of the cell cycle is one of the hallmarks of tumor formation and progression, the newly discovered level of BMS-345541 function could be useful for cell cycle control studies and may provide valuable clues for the design of future therapeutics.

Telomere length in human natural killer cell subsets

Natural killer (NK) cells are cytotoxic cells that play a critical role in the innate immune response against infections and tumors. In the elderly, the cytotoxic function of NK cells is often compromised. Telomeres progressively shorten with each cell division and with age in most somatic cells eventually leading to chromosomal instability and cellular senescence. We studied the telomere length in NK cell subsets isolated from peripheral blood using "flow FISH," a method in which the hybridization of telomere probe in cells of interest is measured relative to internal controls in the same tube. We found that the average telomere length in human NK cells decreased with age as was previously found for human T lymphocytes. Separation of adult NK cells based on CD56 and CD16 expression revealed that the telomere length was significantly shorter in CD56(dim)CD16(+) (mature) NK cells compared to CD56(bright)CD16(-) (immature) NK cells from the same donor. Furthermore, sorting of NK cells based on expression of activation markers, such as NKG2D and LFA-1, revealed that NK cells expressing these markers have significantly shorter telomeres. Telomere fluorescence was very heterogeneous in NK cells expressing CD94, killer inhibitory receptor (KIR), NKG2A, or CD161. Our observations indicate that telomeric DNA in NK cells is lost with cell division and with age similar to what has been observed for most other hematopoietic cells. Telomere attrition in NK cells is a plausible cause for diminished NK cell function in the elderly.

A novel cell compatible impingement system to study in vitro drug absorption from dry powder aerosol formulations

A modified Astra type multistage liquid impinger (MSLI) with integrated bronchial cell monolayers was used to study deposition and subsequent drug absorption on in vitro models of the human airway epithelial barrier. Inverted cell culture of Calu-3 cells on the bottom side of cell culture filter inserts was integrated into a compendial MSLI. Upside down cultivation did not impair the barrier function, morphology and viability of Calu-3 cells. Size selective deposition with subsequent absorption was studied for three different commercially available dry powder formulations of salbutamol sulphate and budesonide. After deposition without size separation the absorption rates from the aerosol formulations differed but correlated with the size of the carrier lactose particles. However, after deposition in the MSLI, simulating relevant impaction and causing the separation of small drug crystals from the carrier lactose, the absorption rates of the three formulations were identical, confirming the bioequivalence of the three formulations.