Amyloid β protein activates PKC-δ and induces translocation of myristoylated alanine-rich C kinase substrate (MARCKS) in microglia

The increased accumulation of activated microglia containing amyloid β protein (Aβ) around senile plaques is a common pathological feature in subjects with Alzheimer's disease (AD). Much less is known, however, of intracellular signal transduction pathways for microglial activation in response to Aβ. We investigated intracellular signaling in response to Aβ stimulation in primary cultured rat microglia. We found that the kinase activity of PKC-δ but not that of PKC- or - is increased by stimulation of microglia with Aβ, with a striking tyrosine phosphorylation of PKC-δ. In microglia stimulated with Aβ, tyrosine phosphorylation of PKC-δ was evident at the membrane fraction without an overt translocation of PKC-δ. PKC-δ co-immunoprecipitated with MARCKS from microglia stimulated with Aβ. Aβ induced translocation of MARCKS from the membrane fraction to the cytosolic fraction. Immunocytochemical analysis revealed that phosphorylated MARCKS accumulated in the cytoplasm, particularly at the perinuclear region in microglia treated with Aβ. Taken together with our previous observations that Aβ-induced phosphorylation of MARCKS and chemotaxis of microglia are inhibited by either tyrosine kinase or PKC inhibitors, our results provide evidence that Aβ induces phosphorylation and translocation of MARCKS through the tyrosine kinase-PKC-δ signaling pathway in microglia.     

Identification and characterization of the precursors committed to osteoclasts induced by TNF-related activation-induced cytokine/receptor activator of NF-kappa B ligand

Osteoclasts are terminally differentiated from cells of monocyte/macrophage lineage by stimulation with TNF-related activation-induced cytokine (TRANCE) (receptor activator of NF-kappaB ligand/osteoprotegerin ligand/osteoclast differentiation factor/TNFSF11/CD254). In the present study, we attempted to determine when and how the cell fate of precursors becomes committed to osteoclasts following TRANCE stimulation. Although mouse bone marrow-derived macrophages (BMMs) were able to differentiate into either osteoclasts or dendritic cells, the cells no longer differentiated into dendritic cells after treatment with TRANCE for 24 h, indicating that their cell fate was committed to osteoclasts. Committed cells as well as BMMs were still quite weak in tartrate-resistant acid phosphatase activity, an osteoclast marker, and incorporated zymosan particles by phagocytosis. Interestingly, committed cells, but not BMMs, could still differentiate into osteoclasts even after incorporation of the zymosan particles. Furthermore, IL-4 and IFN-gamma, potent inhibitors of osteoclast differentiation, failed to inhibit osteoclast differentiation from committed cells, and blocking of TRANCE stimulation by osteoprotegerin resulted in cell death. Adhesion to culture plates was believed to be essential for osteoclast differentiation; however, committed cells, but not BMMs, differentiated into multinucleated osteoclasts without adhesion to culture plates. Although LPS activated the NF-kappaB-mediated pathway in BMMs as well as in committed cells, the mRNA expression level of TNF-alpha in the committed cells was significantly lower than that in BMMs. These results suggest that characteristics of the committed cells induced by TRANCE are distinctively different from that of BMMs and osteoclasts.     

Stereoselective and manganese-dependent sulfation and urinary excretion of -form and -form meta-tyrosine O-sulfate by Sprague–Dawley rats

In our previous studies, we have demonstrated the stereoselective and manganese-dependent sulfation of tyrosine and Dopa isomers by human monoamine (M)-form phenol sulfotransferase (PST). In the present study, we investigated the occurrence of these phenomena in vivo using Sprague–Dawley rats as an experimental model. Three groups of six male rats were orally introduced with 1 ml of, respectively, 3 mM, 10 mM and 30 mM MnCl₂ with a constant level of 0.2 mM -m-tyrosine per day for 7 days. Their urine was collected and analyzed for the presence of sulfated -m-tyrosine ( -m-TyrS) by ion-pair HPLC using a C18 reversed-phase column. The level of urinary -m-TyrS, which was detected in the urine of the MnCl₂-treated rats but not control rats, appeared to increase proportionally to the amount of MnCl₂ administered. Chiral HPLC was employed to differentiate the -form and -form m-TyrS present in the urine sample of MnCl₂-treated rats. Both -m-TyrS and -m-TyrS were detected, with the -form being present at significantly higher level than the -form.     

Characterization of a novel congenic strain of diabetic fatty (WBN/Kob-Lepr(fa)) rat

The WBN/Kob-Lepr^fa rat is a new congenic strain for the fa allele of the leptin receptor gene (Lepr). Homozygous (fa/fa) WBN/Kob-Lepr^fa rats provide a model of non-insulin-dependent diabetes with obesity. Here, we describe the characteristics of this new animal model in detail. At 7 weeks of age, both male and female obese WBN/Kob rats showed inflammatory cell infiltration of the pancreas that suggested pan-pancreatitis and an abnormal OGTT. At 3 months of age, both male and female obese WBN/Kob rats developed overt diabetes mellitus associated with severe chronic pancreatitis. In contrast, lean female WBN/Kob rats do not develop pancreatitis or diabetes. In WBN/Kob rats, this mutation might promote the onset of severe pancreatitis, leading to the rapid development of diabetes mellitus.     

Rectified photocurrent of molecular photodiode consisting of cytochrome c/GFP hetero thin films

Photoinduced electron transfer in the molecular electronic device consisting of protein-adsorbed hetero Langmuir–Blodgett (LB) film was investigated. Three kinds of functional molecules, cytochrome c, viologen, and green fluorescent protein (GFP) were used as an electron acceptor, a mediator, and a sensitizer, respectively. The hetero-LB film was fabricated by subsequently depositing cytochrome c and viologen onto the pretreated ITO or quartz glass. GFP adsorbed hetero-LB films were prepared by soaking the hetero-LB films into the buffer solution containing GFP. The MIM (metal/insulator/metal) structured molecular device was constructed by depositing aluminum onto the surface of the GFP-adsorbed hetero LB films. Due to the excitation by irradiation with a 460 nm monochromic light source, the photoinduced unidirectional flow of electrons in the MIM device could be achieved and was detected as photocurrents. The photoswitching function was achieved and the rectifying characteristic was observed in the molecular device. Based on the measurement of transient photocurrent of molecular device, the unidirectional flow of electrons was verified.     

Effect of chronic administration of fruit extract (Citrus unshiu Marc.) on glucose tolerance in GK rats, a model of type 2 diabetes

Recent epidemiological studies have demonstrated that high dietary consumption of fruit and vegetables results in lower risks of diabetes. In this study, we investigated the effects of chronic administration of fruit extract (Citrus unshiu Marc.) on glucose tolerance in GK rats, a model of type 2 diabetes. After 10 weeks administration of the fruit extract, intraperitoneal glucose tolerance tests revealed significant decrements of blood glucose levels after glucose loading. Our findings further support an advantageous association of fruit consumption with diabetes.     

Soluble FcgammaRIIIa(Mphi) levels in plasma correlate with carotid maximum intima-media thickness (IMT) in subjects undergoing an annual medical checkup

Macrophages play a major role in the development of vascular lesions in atherogenesis. The cells express FcgammaRIIIa (CD16) identical to that in NK cells, but with a cell type-specific glycosylation, and these soluble forms (sFcgammaRIIIa) are present in plasma. We measured sFcgammaRIIIa(Mphi) derived from macrophages in plasma from subjects undergoing an annual medical checkup. The levels of sFcgammaRIIIa(Mphi) increased with age, and correlated positively with body mass index, blood pressure, LDL cholesterol to HDL cholesterol ratio, triglycerides, hemoglobin A1c, and creatinine, but negatively with HDL-cholesterol levels. The sFcgammaRIIIa(Mphi) levels were related to the number of risk factors for atherosclerosis: such as aging, current smoking, diabetes, hypertension, hyper-LDL-cholesterolemia, hypo-HDL-cholesterolemia, and family history of atherosclerotic diseases. In addition, the sFcgammaRIIIa(Mphi) levels were correlated with carotid maximum intima-media thickness (IMT). These findings indicate the macrophages are activated during the incipient stage of atherosclerosis, and suggest sFcgammaRIIIa(Mphi) may be used as a predictive marker for atherosclerosis.