Sei Yoshitatsu, Brandom Barbara W, Bina Saiid, Hosoi Eiji, Gallagher Kathleen L, Wyre Hadley W, Pudimat Paul A, Holman Steve J, Venzon David J, Daly John W, Muldoon Sheila
Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
Anesthesiology. 2002 Nov;97(5):1052-8. doi: 10.1097/00000542-200211000-00005.
Altered Ca2+ homeostasis in skeletal muscle is a key molecular event triggering malignant hyperthermia (MH) in malignant hyperthermia-susceptible (MHS) individuals. Genetic studies have shown that mutations in the type 1 ryanodine receptor (RYR1) are associated with MH susceptibility. Because human B lymphocytes express the RYR1, it is hypothesized that Ca2+ homeostasis in B lymphocytes is altered in MHS individuals.
This study investigated the Ca2+ response of B cells to caffeine and 4-chloro-m-cresol in 13 MHS and 21 MH-negative (MHN) individuals who had been diagnosed by caffeine halothane contracture test (CHCT) and 18 healthy volunteers. Changes in [Ca2+]i in B cells were measured directly in fluo-3 loaded cells using a dual-color flow cytometric technique. Further, B cell phenotype was correlated with CHCT results in a family with the Val2168Met (G6502A) mutation.
Caffeine-induced (50 mm) increases in [Ca2+]i in B cells were significantly greater in MHS than in MHN (P = 0.0004), control (P = 0.0001) or non-MHS (MHN and control) individuals (P < 0.0001). The 4-chloro-m-cresol-induced (400 microm) increases in [Ca2+]i were also significantly different between MHS and controls (P = 0.003) or between MHS and non-MHS (MHN and control) individuals (P = 0.0078). A study of a family with the Val2168Met mutation demonstrated expression of the RYR1 mRNA mutant in B cells from the family members with MHS phenotype and a clear segregation of genotype with B-cell phenotype.
The Ca2+ responses to caffeine or 4-chloro-m-cresol in B lymphocytes showed significant differences between MHS and MHN (or control) individuals. Although the molecular mechanisms of these alterations are currently undetermined, the results suggest that the enhanced Ca2+ responses are associated with mutations in the RYR1 gene in some MHS individuals.
骨骼肌中钙离子稳态的改变是引发恶性高热易感（MHS）个体发生恶性高热（MH）的关键分子事件。遗传学研究表明，1型兰尼碱受体（RYR1）的突变与MH易感性相关。由于人类B淋巴细胞表达RYR1，因此推测MHS个体的B淋巴细胞中钙离子稳态发生了改变。
本研究调查了13例经氟烷咖啡因挛缩试验（CHCT）诊断为MHS的个体、21例MH阴性（MHN）个体以及18名健康志愿者的B细胞对咖啡因和4-氯间甲酚的钙离子反应。使用双色流式细胞术直接测量负载了fluo-3的细胞中B细胞内钙离子浓度（[Ca2+]i）的变化。此外，在一个携带Val2168Met（G6502A）突变的家系中，将B细胞表型与CHCT结果进行了关联分析。
咖啡因（50 mM）诱导的MHS个体B细胞内[Ca2+]i升高显著高于MHN个体（P = 0.0004）、对照组（P = 0.0001）或非MHS个体（MHN和对照组，P < 0.0001）。4-氯间甲酚（400 μM）诱导的MHS个体B细胞内[Ca2+]i升高也与对照组存在显著差异（P = 0.003），或与非MHS个体（MHN和对照组）存在显著差异（P = 0.0078）。对一个携带Val2168Met突变的家系进行的研究表明，具有MHS表型的家系成员的B细胞中存在RYR1 mRNA突变体，并且基因型与B细胞表型明显分离。
MHS个体与MHN个体（或对照组）的B淋巴细胞对咖啡因或4-氯间甲酚的钙离子反应存在显著差异。尽管目前尚不清楚这些改变的分子机制，但结果表明，某些MHS个体中增强的钙离子反应与RYR1基因的突变有关。
