Green L M, Lazarus J P, Song X, Stagg R B, LaBue M, Hilliker S
J.L. Pettis Memorial Veterans Medical Center, Department of Microbiology & Molecular Genetics, Loma Linda University School of Medicine, California 92357, USA.
Thyroid. 1997 Dec;7(6):913-21. doi: 10.1089/thy.1997.7.913.
In the Lewis rat model of experimental autoimmune thyroiditis (EAT), decreased immunodetectable connexin assembly into gap junctions and diminished intercellular communication are associated with the loss of thyroid function (hypothyroidism) that occurs prior to significant tissue destruction. The current study explores the hypothesis that the loss of connexin 43 (Cx43)-mediated intercellular communication in these cells is caused by upregulation of protein kinase C (pKC) activity. Thyrocytes isolated from EAT rats exhibited a 78% increase in basal pKC activity; whereas, basal protein kinase A (pKA) activity was unchanged. Increased pKC activity was a result of increased isozyme protein levels. Thyroid cells expressed pKC isozymes gamma and lambda and had elevated levels of alpha (40%), beta (30%), delta (31%), and epsilon (25%) as quantified by western blot analyses. Furthermore, modulation of pKC activity inversely altered Cx43 assembly and function in monolayer thyrocytes. For example, octoacetyl glycerol (OAG) treatment of normal thyrocyte monolayers to increase pKC activity resulted in deficient Cx43 gap junction assembly and reduced intercellular communication indistinguishable from the deficits in EAT thyrocytes. Conversely, calphostin C inhibition of pKC activity in EAT thyrocyte monolayers restored these parameters to normal. Thus, pharmacological modulations of pKC activity in cultured thyrocytes support a causal relation between the changes in pKC activity and Cx43-mediated intercellular communication. Abnormalities in autoimmune diseased thyroid tissue (eg, increased pKC) appear to contribute to reduced intercellular coordination of thyroid follicles and thereby can affect subsequent thyroid function. The persistence of target cell abnormalities in the absence of infiltrating lymphocytes and their products supports an alternative mechanism by which thyroid function can be affected that does not depend on the loss of thyroid glandular epithelium.
在实验性自身免疫性甲状腺炎（EAT）的Lewis大鼠模型中，免疫检测到的连接蛋白组装成缝隙连接减少以及细胞间通讯减弱，与在显著组织破坏之前发生的甲状腺功能丧失（甲状腺功能减退）有关。当前研究探讨了这样一种假说，即这些细胞中连接蛋白43（Cx43）介导的细胞间通讯丧失是由蛋白激酶C（pKC）活性上调所致。从EAT大鼠分离的甲状腺细胞显示基础pKC活性增加了78%；而基础蛋白激酶A（pKA）活性未改变。pKC活性增加是同工酶蛋白水平升高的结果。甲状腺细胞表达pKC同工酶γ和λ，并且通过蛋白质印迹分析定量显示α（40%）、β（30%）、δ（31%）和ε（25%）水平升高。此外，pKC活性的调节反向改变了单层甲状腺细胞中Cx43的组装和功能。例如，用辛酰乙酰甘油（OAG）处理正常甲状腺细胞单层以增加pKC活性，导致Cx43缝隙连接组装缺陷和细胞间通讯减少，这与EAT甲状腺细胞中的缺陷无法区分。相反，在EAT甲状腺细胞单层中用钙泊三醇C抑制pKC活性可使这些参数恢复正常。因此，培养的甲状腺细胞中pKC活性的药理学调节支持了pKC活性变化与Cx43介导的细胞间通讯之间的因果关系。自身免疫性疾病甲状腺组织中的异常（例如pKC增加）似乎导致甲状腺滤泡细胞间协调减少，从而可能影响随后的甲状腺功能。在没有浸润淋巴细胞及其产物的情况下靶细胞异常的持续存在支持了一种不依赖于甲状腺腺上皮丧失而影响甲状腺功能的替代机制。
