Effects of calmodulin and protein kinase C modulators on transient Ca2+ increase and capacitative Ca2+ entry in human platelets : relevant to pathophysiology of bipolar disorder

Disturbed intracellular calcium (Ca2+) homeostasis has been implicated in bipolar disorder, which mechanisms may be involved in the dysregulation of protein kinase C (PKC) and calmodulin systems. In this study, we investigated a transient intracellular Ca2+ increase induced by thapsigargin, a inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase pump (SERCA), and a capacitative Ca2+ entry followed by addition of extracellular Ca2+, in the presence or absence of PKC/calmodulin modulators in the platelets of healthy subjects in order to elucidate the role of SERCA in Ca2+ homeostasis and to assess how both PKC and calmodulin systems regulate the two Ca2+ responses. Moreover, we also examined the thapsigargin-elicited transient Ca2+ increase and capacitative Ca2+ entry in patients with mood disorders. PKC and calmodulin systems have opposite regulatory effects on the transient Ca2+ increase and capacitative Ca2+ entry in the platelets of normal subjects. The inhibitory effect of PKC activation on capacitative Ca2+ entry is significantly increased and the stimulatory effect of PKC inhibition is significantly decreased in bipolar disorder compared to major depressive disorder and normal controls. These results suggest the possibility that increased PKC activity may activate the inhibitory effect of capacitative Ca2+ entry in bipolar disorder. However, this is a preliminary study using a small sample, thus further studies are needed to examine the PKC and calmodulin modulators on the capacitative Ca2+ entry in a larger sample

Lack of association between XBP1 genotype and calcium signaling in the platelets of healthy subjects

Dysregulations of calcium (Ca) homeostasis may be involved in the pathophysiology of bipolar disorder. Enhanced Ca response to various agonists in peripheral blood cells is one of a few confirmed biological markers for bipolar disorder. Recently, a polymorphism of XBP1, a pivotal gene in the endoplasmic reticulum (ER) stress response, was shown to contribute to the genetic risk factor for bipolar disorder. Thus, in this study, we examined the relationship between the XBP1 gene polymorphism and the Ca signaling in the platelets of healthy controls. The present results suggest no significant difference in the basal Ca level or 5-HT-induced Ca mobilization among normal subjects with -116C/C, C/G and G/G genotypes. Further investigations are necessary to examine the relationship in the different peripheral blood cells and/or in larger samples from patients with bipolar disorder.http://www.sciencedirect.com/science/journal/0304394

Relationship between XBP1 genotype and personality traits assessed by TCI and NEO-FFI

There have been several researches on the role of personality in the pathophysiology of bipolar disorder. Recently, a polymorphism of XBP1, a pivotal gene in the endoplasmic reticulum (ER) stress response, was shown to contribute to the genetic risk factor for bipolar disorder. Therefore, in this study, we examined the relationship between the XBP1 gene polymorphism and the personality traits assessed by two self-rating scales, a shortened version of Temperament and Character Inventory (TCI) and NEO-Five Factor Inventory (NEO-FFI) in healthy subjects. The present results suggested that the XBP1 gene polymorphism was associated with the NEO-FFI score of neuroticism in female subjects. However, no significant differences in the other personality scale scores of both assessments were observed among normal subjects with -116C/C, C/G and G/G genotypes. Further investigations are necessary to examine the relationship in patients with bipolar disorder, or use full version of various self-rating personality assessments