Shigeto Hayashi

Superoxide production at phagosomal cup/phagosome through βI protein kinase C during FcγR-mediated phagocytosis in microglia

Protein kinase C (PKC) plays a prominent role in immune signaling. To elucidate the signal transduction in a respiratory burst and isoform-specific function of PKC during FcγR-mediated phagocytosis, we used live, digital fluorescence imaging of mouse microglial cells expressing GFP-tagged molecules. βI PKC, εPKC, and diacylglycerol kinase (DGK) β dynamically and transiently accumulated around IgG-opsonized beads (BIgG). Moreover, the accumulation of p47phox, an essential cytosolic component of NADPH oxidase and a substrate for βI PKC, at the phagosomal cup/phagosome was apparent during BIgG ingestion. Superoxide (O2−) production was profoundly inhibited by Gö6976, a cPKC inhibitor, and dramatically increased by the DGK inhibitor, R59949. Ultrastructural analysis revealed that BIgG induced O2− production at the phagosome but not at the intracellular granules. We conclude that activation/accumulation of βI PKC is involved in O2− production, and that O2− production is primarily initiated at the phagosomal cup/phagosome. This study also suggests that DGKβ plays a prominent role in regulation of O2− production during FcγR-mediated phagocytosis.

Involvement of γ protein kinase C in estrogen-induced neuroprotection against focal brain ischemia through G protein-coupled estrogen receptor

The neuroprotective effects of estrogen were studied in the ischemic model mice by 90 min transient unilateral middle cerebral artery occlusion (MCAO) followed by 22.5 h reperfusion. The total infarct size in C57BL/6 female mice after MCAO and reperfusion was significantly smaller than that in male mice. Intraperitoneal injection of estrogen after the start of reperfusion significantly reduced the infarct volume in the male mice. However, no significant gender difference was found in total infarct size in γ protein kinase C (PKC)‐knockout mice, suggesting that the neuroprotective effects of estrogen are due to the activation of a specific subtype of PKC, γPKC, a neuron‐specific PKC subtype, in the brain. We demonstrated that exogenous estrogen‐induced neuroprotection was attenuated in γPKC‐knockout mice. Immunocytochemical study showed that γPKC was translocated to nerve fiber‐like structures when observed shortly after MCAO and reperfusion. We also visualized the rapid and reversible translocation of γPKC‐GFP (green fluorescent protein) by estrogen stimulation in living CHO‐K1 cells. These results suggest that the activation of γPKC through the G‐protein‐coupled estrogen receptors on the plasma membrane is involved in the estrogen‐induced neuroprotection against focal brain ischemia.

Skull metastasis as initial manifestation of pulmonary epithelial-myoepithelial carcinoma: a case report of an unusual case.

Epithelial-myoepithelial carcinoma (EMC) of the lung is rare and is considered to be low-grade malignancy. Intracranial metastasis of pulmonary EMC has not previously been reported according to our search of the literature. We report a case of skull metastasis as the initial manifestation of pulmonary EMC. An 81-year-old man complained of left leg motor weakness. Neurological examination showed left hemiparesis. Computed tomography and magnetic resonance imaging revealed an osteolytic tumor in the right frontal bone with invasion to the dura and subdural space, attached to the superior sagittal sinus. Subtotal removal of the tumor was performed, and the left hemiparesis showed improvement. Histopathological study revealed the tumor to consist of epithelial and myoepithelial cells. Pulmonary EMC was diagnosed. The MIB-1 index in primary lesion was approximately 10%. The skull and dura are possible sites for metastasis from pulmonary EMC. The MIB-1 index is a predictive marker of malignant potential.

Rapid tumor growth with glial differentiation of central neurocytoma after stereotactic radiosurgery

Although stereotactic radiosurgery (SRS) is effective for central neurocytoma (CN), the long-term outcome of SRS remains unclear. We present a case of recurrent CN that was diagnosed 10years after surgical resection and consecutive stereotactic radiotherapy. The patient was treated with SRS for the recurrent tumor, but underwent two-staged surgery once again due to rapid tumor growth. Histological features of the recurrent tumor were consistent with the diagnosis of CN. However, an increased Ki-67 proliferation index (3.4%), aberrant angiogenesis and glial differentiation of the tumor cells were observed, which were not identified in the initial CN. In addition, vascular endothelial growth factor (VEGF) and VEGF receptor were highly expressed in the recurrent tumor cells, as well as in the vascular endothelial cells. Our case suggests that malignant transition with aberrant angiogenesis and glial differentiation may be attributable to SRS.