Ethanol induces apoptosis in human mast cells.

AIMS

Alcohol abuse is associated with increased frequency of infections attributed to ethanol-induced immune suppression. The precise mechanism of immune suppression is however not known. Mast cells (MC) belong to the innate immune system and they have been implicated in the first line of immune defence against bacteria and parasites. Therefore we studied the effects of ethanol and its first metabolite acetaldehyde on mast cell viability, proliferation and apoptosis.

MAIN METHODS

Human mast cell line (HMC)-1 cells, mouse bone marrow derived mast cells (mBMMC) and human peripheral blood derived mast cells (HuMC) were used. Effects of ethanol and acetaldehyde on mast cell proliferation were determined by assessing incorporation of [(3)H]thymidine into cellular DNA and by trypan blue exclusion. Apoptosis was assessed by measuring apoptotic nucleosomes and caspase-3, -8 and -9 activities using ELISA and by using Tunel assay. The expression of anti- and proapoptotic proteins Bcl-2 and Bax was analyzed by RT-PCR and western blot, respectively.

KEY FINDINGS

Ethanol, but not acetaldehyde inhibited dose-dependently the proliferation and viability HMC-1 and mBMMC cells. The decreased viability was caused by apoptotic cell death of the MC. Significant apoptosis of HMC-1 cells was observed in the presence of 43mM (2.5 per thousand) ethanol. Induction of apoptosis was associated with clearly increased caspase-3 activity and moderately increased caspase-8 and 9 activities. Ethanol also shifted the Bcl-2/Bax balance towards apoptosis.

SIGNIFICANCE

The ethanol-induced reduction of MC viability could contribute to immunosuppression associated with ethanol abuse.