RESUMO
BACKGROUND: GABA(A) receptors are members of the Cys-loop family of neurotransmitter receptors, proteins which are responsible for fast synaptic transmission, and are the site of action of wide range of drugs. Recent work has shown that Cys-loop receptors are present on immune cells, but their physiological roles and the effects of drugs that modify their function in the innate immune system are currently unclear. We are interested in how and why anaesthetics increase infections in intensive care patients; a serious problem as more than 50% of patients with severe sepsis will die. As many anaesthetics act via GABA(A) receptors, the aim of this study was to determine if these receptors are present on immune cells, and could play a role in immunocompromising patients. PRINCIPAL FINDINGS: We demonstrate, using RT-PCR, that monocytes express GABA(A) receptors constructed of α1, α4, ß2, γ1 and/or δ subunits. Whole cell patch clamp electrophysiological studies show that GABA can activate these receptors, resulting in the opening of a chloride-selective channel; activation is inhibited by the GABA(A) receptor antagonists bicuculline and picrotoxin, but not enhanced by the positive modulator diazepam. The anaesthetic drugs propofol and thiopental, which can act via GABA(A) receptors, impaired monocyte function in classic immunological chemotaxis and phagocytosis assays, an effect reversed by bicuculline and picrotoxin. SIGNIFICANCE: Our results show that functional GABA(A) receptors are present on monocytes with properties similar to CNS GABA(A) receptors. The functional data provide a possible explanation as to why chronic propofol and thiopental administration can increase the risk of infection in critically ill patients: their action on GABA(A) receptors inhibits normal monocyte behaviour. The data also suggest a potential solution: monocyte GABA(A) receptors are insensitive to diazepam, thus the use of benzodiazepines as an alternative anesthetising agent may be advantageous where infection is a life threatening problem.
Assuntos
Anestésicos/efeitos adversos , Doenças do Sistema Imunitário/induzido quimicamente , Sistema Imunitário/efeitos dos fármacos , Receptores de GABA-A/fisiologia , Anestésicos/farmacologia , Bicuculina/farmacologia , Linhagem Celular , Receptores de Canais Iônicos de Abertura Ativada por Ligante com Alça de Cisteína/agonistas , Receptores de Canais Iônicos de Abertura Ativada por Ligante com Alça de Cisteína/genética , Receptores de Canais Iônicos de Abertura Ativada por Ligante com Alça de Cisteína/metabolismo , Receptores de Canais Iônicos de Abertura Ativada por Ligante com Alça de Cisteína/fisiologia , Avaliação Pré-Clínica de Medicamentos , Antagonistas GABAérgicos/farmacologia , Agonistas de Receptores de GABA-A/farmacologia , Humanos , Sistema Imunitário/metabolismo , Sistema Imunitário/fisiologia , Doenças do Sistema Imunitário/genética , Doenças do Sistema Imunitário/metabolismo , Hospedeiro Imunocomprometido/efeitos dos fármacos , Hospedeiro Imunocomprometido/imunologia , Monócitos/efeitos dos fármacos , Monócitos/imunologia , Monócitos/metabolismo , Monócitos/fisiologia , Muscimol/farmacologia , Picrotoxina/farmacologia , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genética , Transmissão Sináptica/fisiologiaRESUMO
The identification of markers for the isolation of human neural stem cells (hNSCs) is essential for studies of their biology and therapeutic applications. This study investigated expression of the integrin receptor family by hNSCs as potential markers. Selection of alpha6(hi) or beta1(hi) cells by fluorescence-activated cell sorting led to an enrichment of human neural precursors, as shown by both neurosphere forming assays and increased expression of prominin-1, sox2, sox3, nestin, bmi1, and musashi1 in the beta1(hi) population. Cells expressing high levels of beta1 integrin also expressed prominin-1 (CD133), a marker previously used to isolate hNSCs, and selection using integrin beta1(hi) cells or prominin-1(hi) cells was found to be equally effective at enriching for hNSCs from neurospheres. Therefore, integrin subunits alpha6 and beta1 are highly expressed by human neural precursors and represent convenient markers for their prospective isolation.
