Kazuya Ikematsu

Induction of nitric oxide synthase by traumatic brain injury

We investigated the dynamic induction/expression of inducible nitric oxide synthase (iNOS) using human brains made available through death by traumatic brain injury (TBI). Astrocytes, microglia, and neutrophils were identified in tissue using immunohistochemical staining with antibodies against glial fibrillary acidic protein (GFAP), MHC class II antigen, and neutrophil elastase, respectively. The localization of iNOS protein in each of these cell types was evaluated using immunohistochemistry. Within 2 days of injury, iNOS immunoreactivity was not detected. However, after 2 days, immunoreactivity was detected in the traumatized brain. The iNOS immunoreactivity was localized on neutrophils and microglia/macrophages in the areas around the tissue necrosis in the traumatized cortical hemisphere, in the deep part of the cortex and the dentate gyri of the hippocampi adjacent to the hemorrhage, and within the cytoplasm of vascular smooth muscle cell of a small artery or arteriole surrounding the injured region. This reactivity was absent after 8 days post-injury.These observations confirmed the prolonged induction of iNOS within various cells in the injured brain. These responses suggest that iNOS plays a crucial role in cerebrovascular damage and/or secondary brain damage subsequent to traumatic brain injury. Furthermore, the dense nitric oxide (NO) generated by iNOS may play a role in neuronal cell death after injury.

Age-associated increases in heme oxygenase-1 and ferritin immunoreactivity in the autopsied brain

Heme oxygenase-1 (HO-1) is a 32 kDa heat shock protein (HSP) that catalyzes heme to biliverdin, free iron and carbon monoxide in the brain. Furthermore, the release of free ferrous ion by HO-1 plays an essential role in ferritin synthesis, and ferritin stores iron either for intracellular utilization, or for detoxification. It is well known that HO-1 immunoreactivity is enhanced greatly in neurons and glia of the hippocampus and cerebral cortex in various pathophysiological conditions. The expression of HSP 70 is well known for the age-associated increase, but the expression modalities of HO-1 and ferritin associated with aging are still unknown. A study was therefore performed to examine the correlations in the expression of HO-1 and ferritin with age using immunohistochemistry. We investigated 31 autopsied brains (3-84-year-olds) without traumatic brain injury and neurodegenerative disease. The specimens were taken from the cerebral cortex and hippocampus. In the cerebral cortex, age (aging) had a statistically significant positive correlation with HO-1 (r=0.894, P<0.01) and ferritin (r=0.731, P<0.01). In the hippocampus, age had a significant positive correlation with only HO-1 (r=0.660, P<0.01). These results showed that HO-1 and ferritin underwent an age-related increase in human brain, especially in the cerebral cortex. Our results also indicate that various stress responses may persist in the aged human brain.

Vesicular nucleotide transporter is involved in ATP storage of secretory lysosomes in astrocytes.

Recent studies have suggested that astrocytes release gliotransmitters (i.e., ATP, L-glutamate, D-serine, and peptide hormones) and participate actively in synaptic functioning. Although ATP release from astrocytes modulates the activity of neurons, the mechanisms regulating the ATP release from astrocytes and the source of ATP in astrocytes are not well understood. Recently a vesicular nucleotide transporter (VNUT)/solute carrier family 17, member 9 (SLC17A9) has been identified as a mediator of the active accumulation of ATP into vesicles. Here we show by immunocytochemical analysis under confocal microscope and live cell imaging under total internal reflection fluorescence microscope that lysosome-associated VNUT is responsible for ATP release in astrocytes. VNUT was expressed in both primary cultured cortical astrocytes and glioma cell line C6 cells, and mainly localized on lysosome in the cells. We found that VNUT-associated secretory lysosomes do not fully collapse into the plasma membrane after lysosomal exocytosis. We also found that inhibition of VNUT function by Evans Blue decreased ATP uptake into secretory lysosomes. Depletion and inhibition of endogenous VNUT by small interference RNA and Evans Blue, respectively decreased the amount of ATP release from the cells, whereas overexpression of VNUT increased it. Taken together, these findings indicate that the participation of VNUT in ATP storage in secretory lysosomes during lysosomal exocytosis of ATP from astrocytes.

The time-course analysis of gene expression during wound healing in mouse skin.

RNA analysis has been applied to forensic work to determine wound age. We investigated mRNA expression using quantitative RT-PCR of ten genes, including c-fos, fosB, mitogen-activated protein kinase phosphatase-1 (MKP-1), CD14, chemokine (C-C motif) ligand 9 (CCL9), placenta growth factor (PlGF), mast cell protease-5 (MCP-5), growth arrest specific 5 (Gas5), beta-2 microglobulin (B2M) and major urinary protein-1 (MUP-1), in terms of repair response in adult mice. The expression level of c-fos, fosB and MKP-1 transcripts increased drastically, peaked within 1h, and that of the CD14 and CCL9 transcripts peaked from 12 to 24h. An increase in PlGF and MCP-5 mRNA appeared on about day 5. Gas5, B2M and MUP-1 transcripts showed no significant change. Each gene had differentially expressional patterns with time-course. Our result implied that the observation of the 7 genes in wounded skin could serve to aid in the accurate diagnosis of wound age.

Release of TNF-α from macrophages is mediated by small GTPase Rab37

Activated macrophages at wound sites release many cytokines which positively affect skin wound healing. However, the molecular mechanisms controlling cytokine secretion from macrophages have not been elucidated. In the present study, we performed an RT‐PCR analysis and found that 19 small GTPase Rab isoforms were expressed at skin wound sites, with six of them (i.e. Rab3B, Rab27B, Rab30, Rab33A, Rab37, and Rab40C) being upregulated during the inflammation and proliferation/migration phase of skin repair. We also found that gene expression of Rab37 in murine primary and RAW264.7 macrophages was significantly induced after stimulation with LPS. Overexpression of wild type and constitutively active Rab37 in RAW264.7 cells significantly increased TNF‐α secretion, whereas knockdown of Rab37 by siRNA significantly decreased it. We also identified 29 putative Rab37‐interacting proteins, including the membrane fusion regulating Munc13‐1, using liquid chromatography/linear ion trap mass spectrometry (LC‐MS/MS). Immunocytochemical analysis further revealed that TNF‐α‐containing vesicles were colocalized with both Rab37 and Munc13‐1 in activated macrophages. Knockdown of Munc13‐1 by siRNA significantly decreased TNF‐α secretion. Taken together, these findings demonstrate that Rab37 interacts with Munc13‐1 to control TNF‐α secretion from activated macrophages.

Reduced FOXO1 expression accelerates skin wound healing and attenuates scarring.

The forkhead box O (FOXO) family has been extensively investigated in aging and metabolism, but its role in tissue-repair processes remains largely unknown. Herein, we clarify the molecular aspect of the FOXO family in skin wound healing. We demonstrated that Foxo1 and Foxo3a were both up-regulated during murine skin wound healing. Partial knockout of Foxo1 in Foxo1(+/-) mice throughout the body led to accelerated skin wound healing with enhanced keratinocyte migration, reduced granulation tissue formation, and decreased collagen density, accompanied by an attenuated inflammatory response, but we observed no wound phenotype in Foxo3a(-/-) mice. Fibroblast growth factor 2, adiponectin, and notch1 genes were significantly increased at wound sites in Foxo1(+/-) mice, along with markedly altered extracellular signal-regulated kinase 1/2 and AKT phosphorylation. Similarly, transient knockdown of Foxo1 at the wound site by local delivery of antisense oligodeoxynucleotides enhanced skin wound healing. The link between FOXO1 and scarring extends to patients, in particular keloid scars, where we see FOXO1 expression markedly increased in fibroblasts and inflammatory cells within the otherwise normal dermis. This occurs in the immediate vicinity of the keloid by comparison to the center of the mature keloid, indicating that FOXO1 is associated with the overgrowth of this fibrotic response into adjacent normal skin. Overall, our data indicate that molecular targeting of FOXO1 may improve the quality of healing and reduce pathological scarring.

Autopsy report for a caffeine intoxication case and review of the current literature

Caffeine (1,3,7-trimethylxanthine) is a popular mild central nervous system stimulant found in the leaves, seeds and fruits of various plants and in foodstuffs such as coffee, tea, and chocolate, among others. Caffeine is widely used and is not associated with severe side effects when consumed at relatively low doses. Although rarely observed, overdoses can occur. However, only a few fatal caffeine intoxication cases have been reported in the literature. Herein, we report the pathological examination results and information on caffeine concentrations in the blood, urine and main organs in a fatal caffeine intoxication case. Even though high caffeine concentrations were found in the systemic organs, no caffeine-related pathological changes were detected.

The expression of excitatory amino acid transporter 2 in traumatic brain injury

It is well recognized that glutamate is the major excitatory neurotransmitter, which is removed from the synaptic cleft by excitatory amino acid transporter 2 (EAAT2) located on the perisynaptic astrocytes and that neuronal death has been associated with an increased extracellular glutamate concentration. In this study, we have immunohistochemically demonstrated the expression of EAAT2 protein in the human brain after traumatic brain injury (TBI). The EAAT2 expression patterns can be divided into three types: continuous and highly extensive staining (E); continuous but sporadic staining (M); and sporadic pattern staining (S). In six of the nine short survival cases studied (1 h to 1 day), continuous and highly extensive staining for EAAT2 (E type) was observed in the ipsilateral cerebral cortex. On the other hand, we were able to demonstrate weak staining (S and M types) in 5 of the 7 long survival cases (> or =1 day) and in 12 of the 14 very short survival cases (<1 h) studied. Similar findings were obtained in the contralateral cerebral cortex and also in the ipsilateral hippocampus. In addition, positive staining for glial fibrillary acidic protein was detected around the cerebral contusion, but the EAAT2-positive expression was not observed in the same region for all of the six short and long survival cases (> or =1 h) after TBI. These findings clearly showed the differences in EAAT2 expression in the cerebral cortex according to the survival time and severity of cerebral contusion after TBI. Therefore, we emphasized that EAAT2 might play an important role in contributing to extracellular glutamate concentrations and secondary brain injury after TBI.

C-fos, fos-B, c-jun and dusp-1 expression in the mouse heart after single and repeated methamphetamine administration

In forensic autopsy, there are numerous sudden methamphetamine (MA)-related deaths. The concentration of MA in the blood is measured to determine the cause of death in case of MA-related death. As a low concentration of MA is detected in MA-related death cases, it is sometimes difficult to identify to the cause of death. MA abusers often exhibit various cardiovascular diseases. MA induces arrhythmia and morphological change in cultured cardiomyocytes. Therefore, MA might affect heart cells, especially in terms of gene expression. Immediate early genes (IEGs) are expressed before some specific gene expressions following certain stimuli. We investigated the expression of IEGs, including c-fos, fos-B, c-jun and dusp-1 mRNA, in the mouse heart after a once-daily MA injection for 1day, 2 or 4weeks using real-time quantitative PCR. We showed that high-dose (10mg/kg) MA administration on day 1 induced mRNA expression of the four IEGs. In contrast, low-dose (1mg/kg) administration on day 1 did not induce any c-fos expression. These findings were characteristic only of the heart, since c-fos increased after treatment at any dose in the brain, suggesting that the intracellular signal cascade differs in these two organs. Nevertheless, we confirmed the transcriptional tolerance in the heart as well as the brain on chronic administration by investigating IEG expression. We were unable to explain why the expressions of IEGs were similar between both doses of MA after chronic administration, although these differed after the single treatment. Additionally, these results strongly suggest that the transcriptome must be altered after long-term treatment. As MA abuse results in various cardiovascular diseases, investigation of the transcriptome in the heart after chronic MA administration will aid in elucidating the patho-physiology of MA-related cardiovascular disease.

The small GTPase Cdc42 modulates the number of exocytosis-competent dense-core vesicles in PC12 cells

Although the small GTPase Rho family Cdc42 has been shown to facilitate exocytosis through increasing the amount of hormones released, the precise mechanisms regulating the quantity of hormones released on exocytosis are not well understood. Here we show by live cell imaging analysis under TIRF microscope and immunocytochemical analysis under confocal microscope that Cdc42 modulated the number of fusion events and the number of dense-core vesicles produced in the cells. Overexpression of a wild-type or constitutively-active form of Cdc42 strongly facilitated high-KCl-induced exocytosis from the newly recruited plasma membrane vesicles in PC12 cells. By contrast, a dominant-negative form of Cdc42 inhibited exocytosis from both the newly recruited and previously docked plasma membrane vesicles. The number of intracellular dense-core vesicles was increased by the overexpression of both a wild-type and constitutively-active form of Cdc42. Consistently, activation of Cdc42 by overexpression of Tuba, a Golgi-associated guanine nucleotide exchange factor for Cdc42 increased the number of intracellular dense-core vesicles, whereas inhibition of Cdc42 by overexpression of the Cdc42/Rac interactive binding domain of neuronal Wiskott-Aldrich syndrome protein decreased the number of them. These findings suggest that Cdc42 facilitates exocytosis by modulating both the number of exocytosis-competent dense-core vesicles and the production of dense-core vesicles in PC12 cells.