Quantitative imaging mass spectroscopy reveals roles of heme oxygenase-2 for protecting against transhemispheric diaschisis in the brain ischemia.

Carbon monoxide-generating heme oxygenase-2 is expressed in neurons and plays a crucial role for regulating hypoxic vasodilation through mechanisms unlocking carbon monoxide-dependent inhibition of H2S-generating cystathionine ß-synthase expressed in astrocytes. This study aims to examine whether heme oxygenase-2 plays a protective role in mice against stroke. Focal ischemia was induced by middle cerebral artery occlusion. Regional differences in metabolites among ipsilateral and contralateral hemispheres were analysed by quantitative imaging mass spectrometry equipped with an image-processing platform to optimize comparison of local metabolite contents among different animals. Under normoxia, blood flow velocity in precapillary arterioles were significantly elevated in heme oxygenase-2-null mice vs controls, while metabolic intermediates of central carbon metabolism and glutamate synthesis were elevated in the brain of heme oxygenase-2-null mice, suggesting greater metabolic demands to induce hyperemia in these mice. In response to focal ischemia, heme oxygenase-2-null mice exhibited greater regions of ischemic core that coincide with notable decreases in energy metabolism in the contralateral hemisphere as well as in penumbra. In conclusion, these findings suggest that heme oxygenase-2 is involved in mechanisms by which not only protects against compromised energy metabolism of the ipsilateral hemisphere but also ameliorates transhemispheric diaschisis of the contralateral hemisphere in ischemic brain.

CO-CBS-H2 S Axis: From Vascular Mediator to Cancer Regulator.

CO is a gaseous mediator generated by HO. Our previous studies revealed that CO generated from inducible HO-1 or from constitutive HO-2 modulates function of different heme proteins or enzymes through binding to their prosthetic ferrous heme to alter their structures, regulating biological function of cells and organs. Such CO-directed target macromolecules include sGC and CBS. In the liver, CO serves as a sinusoidal dilator through its action on sGC in hepatic stellate cells, while the same gas accounts for vasoconstrictor that inhibits H2S generated by CO-sensitive CBS in astrocytes. Since molecular O2 is a substrate for HO, the latter mechanism contributes to hypoxic vasodilation in neurovascular units. We have recently uncovered that stress-inducible CO in and around cancer cells suppresses CBS to result in decreased methylation of PFKFB3, the enzyme regulating PFK-1, leading to a shift of glucose biotransformation from glycolysis toward pentose phosphate pathway; such a metabolic remodeling causes chemoresistance through increasing NADPH and reduced glutathione under stress conditions for cancer cells. This article reviews the intriguing networks of CO-sensitive metabolic regulatory mechanisms in microcirculation and cancer.

A possible role of microglia-derived nitric oxide by lipopolysaccharide in activation of astroglial pentose-phosphate pathway via the Keap1/Nrf2 system.

BACKGROUND: Toll-like receptor 4 (TLR4) plays a pivotal role in the pathophysiology of stroke-induced inflammation. Both astroglia and microglia express TLR4, and endogenous ligands produced in the ischemic brain induce inflammatory responses. Reactive oxygen species (ROS), nitric oxide (NO), and inflammatory cytokines produced by TLR4 activation play harmful roles in neuronal damage after stroke. Although astroglia exhibit pro-inflammatory responses upon TLR4 stimulation by lipopolysaccharide (LPS), they may also play cytoprotective roles via the activation of the pentose phosphate pathway (PPP), reducing oxidative stress by glutathione peroxidase. We investigated the mechanisms by which astroglia reduce oxidative stress via the activation of PPP, using TLR4 stimulation and hypoxia in concert with microglia. METHODS: In vitro experiments were performed using cells prepared from Sprague-Dawley rats. Coexisting microglia in the astroglial culture were chemically eliminated using L-leucine methyl ester (LME). Cells were exposed to LPS (0.01 µg/mL) or hypoxia (1 % O2) for 12-15 h. PPP activity was measured using [1-(14)C]glucose and [6-(14)C]glucose. ROS and NO production were measured using 2',7'-dichlorodihydrofluorescein diacetate and diaminofluorescein-FM diacetate, respectively. The involvement of nuclear factor-erythroid-2-related factor 2 (Nrf2), a cardinal transcriptional factor under stress conditions that regulates glucose 6-phosphate dehydrogenase, the rate-limiting enzyme of PPP, was evaluated using immunohistochemistry. RESULTS: Cultured astroglia exposed to LPS elicited 20 % increases in PPP flux, and these actions of astroglia appeared to involve Nrf2. However, the chemical depletion of coexisting microglia eliminated both increases in PPP and astroglial nuclear translocation of Nrf2. LPS induced ROS and NO production in the astroglial culture containing microglia but not in the microglia-depleted astroglial culture. LPS enhanced astroglial ROS production after glutathione depletion. U0126, an upstream inhibitor of mitogen-activated protein kinase, eliminated LPS-induced NO production, whereas ROS production was unaffected. U0126 also eliminated LPS-induced PPP activation in astroglial-microglial culture, indicating that microglia-derived NO mediated astroglial PPP activation. Hypoxia induced astroglial PPP activation independent of the microglia-NO pathway. Elimination of ROS and NO production by sulforaphane, a natural Nrf2 activator, confirmed the astroglial protective mechanism. CONCLUSIONS: Astroglia in concert with microglia may play a cytoprotective role for countering oxidative stress in stroke.

Leukocyte plugging and cortical capillary flow after subarachnoid hemorrhage.

BACKGROUND: It is believed that increased intracranial pressure immediately after subarachnoid hemorrhage (SAH) causes extensive brain ischemia and results in worsening clinical status. Arterial flow to the cerebral surfaces is clinically well maintained during clipping surgery regardless of the severity of the World Federation of Neurological Societies grade after SAH. To explore what kinds of changes occur in the cortical microcirculation, not at the cerebral surface, we examined cortical microcirculation after SAH using two-photon laser scanning microscopy (TPLSM). METHODS: SAH was induced in mice with an endovascular perforation model. Following continuous injection of rhodamine 6G, velocities of labeled platelets and leukocytes and unlabeled red blood cells (RBCs) were measured in the cortical capillaries 60 min after SAH with a line-scan method using TPLSM, and the data were compared to a sham group and P-selectin monoclonal antibody-treated group. RESULTS: Velocities of leukocytes, platelets, and RBCs in capillaries decreased significantly 60 min after SAH. Rolling and adherent leukocytes suddenly prevented other blood cells from flowing in the capillaries. Flowing blood cells also decreased significantly in each capillary after SAH. This no-reflow phenomenon induced by plugging leukocytes was often observed in the SAH group but not in the sham group. The decreased velocities of blood cells were reversed by pretreatment with the monoclonal antibody of P-selection, an adhesion molecule expressed on the surfaces of both endothelial cells and platelets. CONCLUSIONS: SAH caused sudden worsening of cortical microcirculation at the onset. Leukocyte plugging in capillaries is one of the reasons why cortical microcirculation is aggravated after SAH.

Hypoxic regulation of the cerebral microcirculation is mediated by a carbon monoxide-sensitive hydrogen sulfide pathway.

Enhancement of cerebral blood flow by hypoxia is critical for brain function, but signaling systems underlying its regulation have been unclear. We report a pathway mediating hypoxia-induced cerebral vasodilation in studies monitoring vascular disposition in cerebellar slices and in intact mouse brains using two-photon intravital laser scanning microscopy. In this cascade, hypoxia elicits cerebral vasodilation via the coordinate actions of H(2)S formed by cystathionine ß-synthase (CBS) and CO generated by heme oxygenase (HO)-2. Hypoxia diminishes CO generation by HO-2, an oxygen sensor. The constitutive CO physiologically inhibits CBS, and hypoxia leads to increased levels of H(2)S that mediate the vasodilation of precapillary arterioles. Mice with targeted deletion of HO-2 or CBS display impaired vascular responses to hypoxia. Thus, in intact adult brain cerebral cortex of HO-2-null mice, imaging mass spectrometry reveals an impaired ability to maintain ATP levels on hypoxia.

Visualization and quantification of cerebral metabolic fluxes of glucose in awake mice.

Biotransformation of glucose in organs includes multiple pathways, while quantitative evaluation of percentages of its utilization for individual pathways and their spatial heterogeneity in vivo remain unknown. Imaging MS (IMS) and metabolomics combined with a focused microwave irradiation for rapidly fixing tissue metabolism allowed us to quantify and visualize metabolic fluxes of glucose-derived metabolites in the mouse brain in vivo. At 15 min after the intraperitoneal injection of (13) C6 -labeled glucose, the mouse brain was exposed to focused microwave irradiation, which can stop brain metabolism within 1 s. Quantification of metabolic intermediates containing (13) C atoms revealed that a majority of the (13) C6 -glucose was diverted into syntheses of glutamate, lactate, and uridine diphosphate (UDP)-glucose. IMS showed that regions rich in glutaminergic neurons exhibited a large signal of (13) C2 -labeled glutamate. On the other hand, the midbrain region was enriched with an intensive (13) C6 -labeled UDP-glucose signal, suggesting an active glycogen synthesis. Collectively, application of the current method makes it possible to examine the fluxes of glucose metabolism in a region-specific manner.

TOF-SIMS imaging of halide/thiocyanate anions and hydrogen sulfide in mouse kidney sections using silver-deposited plates.

In vivo imaging of reactive small molecule metabolites with high spatial resolution and specificity could give clues to understanding pathophysiology of various diseases. We herein applied time of flight-secondary ion mass spectrometry (TOF-SIMS) to newly developed silver-deposited plates that were stamped on mouse tissues, and succeeded in visualization of halide (Cl(-), Br(-), and I(-)) and pseudohalide thiocyanate (SCN(-)) anions, a class of substrates for neutrophils/eosinophil peroxidases to produce hypohalous acids (HOX/OX(-) mixture; X: (pseudo)halides), as well as hydrogen sulfide (H(2)S). Forty-micrometer frozen mouse kidney sections on cover glasses were attached to 37 °C preheated silver-deposited plates and incubated at -10 °C for 1 h. After sputter cleaning to remove surface contaminants, the plates were analyzed by TOF-SIMS to identify distribution of Br(-), AgBr(2)(-), I(-), AgI(2)(-), SCN(-), as well as S(2-) and AgS(-) as products of tissue-derived H(2)S. Br(-), AgBr(2)(-), I(-), and SCN(-) anions were mainly distributed in core regions including the inner medulla and inner stripe of the outer medulla (except for I(-)), rather than outer regions such as the cortex and outer stripe of the outer medulla. AgI(2)(-) anion was spread over the whole kidney, although its levels were relatively low. In contrast, S(2-) and AgS(-) anions were mainly present in the outer regions. To our knowledge, this is the first imaging study to reveal the distribution of (pseudo)halides and H(2)S in animal tissue sections.

Hypoxia-sensitive fluorescent probes for in vivo real-time fluorescence imaging of acute ischemia.

Based on the findings that the azo functional group has excellent properties as the hypoxia-sensor moiety, we developed hypoxia-sensitive near-infrared fluorescent probes in which a large fluorescence increase is triggered by the cleavage of an azo bond. The probes were used for fluorescence imaging of hypoxic cells and real-time monitoring of ischemia in the liver and kidney of live mice.

Cystathionine beta-synthase as a carbon monoxide-sensitive regulator of bile excretion.

UNLABELLED: Carbon monoxide (CO) is a stress-inducible gas generated by heme oxygenase (HO) eliciting adaptive responses against toxicants; however, mechanisms for its reception remain unknown. Serendipitous observation in metabolome analysis in CO-overproducing livers suggested roles of cystathionine beta-synthase (CBS) that rate-limits transsulfuration pathway and H(2)S generation, for the gas-responsive receptor. Studies using recombinant CBS indicated that CO binds to the prosthetic heme, stabilizing 6-coordinated CO-Fe(II)-histidine complex to block the activity, whereas nitric oxide (NO) forms 5-coordinated structure without inhibiting it. The CO-overproducing livers down-regulated H(2)S to stimulate HCO(3) (-)-dependent choleresis: these responses were attenuated by blocking HO or by donating H(2)S. Livers of heterozygous CBS knockout mice neither down-regulated H(2)S nor exhibited the choleresis while overproducing CO. In the mouse model of estradiol-induced cholestasis, CO overproduction by inducing HO-1 significantly improved the bile output through stimulating HCO(3) (-) excretion; such a choleretic response did not occur in the knockout mice. CONCLUSION: Results collected from metabolome analyses suggested that CBS serves as a CO-sensitive modulator of H(2)S to support biliary excretion, shedding light on a putative role of the enzyme for stress-elicited adaptive response against bile-dependent detoxification processes.

The effects of cilostazol on tissue oxygenation upon an ischemic-reperfusion injury in the mouse cerebrum.

Although cilostazol, an inhibitor of cyclic nucleotide phosphodiesterase 3 (PDE3), is known to exert a potent antiplatelet function by raising intracellular cAMP concentration, its effect on cerebral microcirculation upon an ischemic insult is not clearly understood. To examine effects of cilostazol on the global ischemic injury in the brain, we first measured the plasma leakage using modified Miles assay after mice had been subjected to 60 min of a bilateral common carotid artery (BCCA) occlusion followed by reperfusion for 4 h. Oral treatment with cilostazol (30 mg/kg) significantly increased plasma leakage. This result led us to examine if the treatment with cilostazol recruits more capillaries leading to an increase in surface area for exchange and oxygen transport to tissues. To do so, we simultaneously measured degrees of tissue hypoxia and vessel perfusion. Pimonidazol was injected intraperitoneally 1 h before sacrifice and capillary patency was assessed by fluorescein isothiocyanate-labeled Lycopersicon esculentum lectin bound to the endothelial surface. Treatment with cilostazol markedly increased the capillary patency which was accompanied by a reduction in the hypoxic area. Although the treatment with cilostazol caused an increase in the flux of plasma proteins across endothelial barrier that may imply an adverse role after a BCCA occlusion, this increase in protein leakage was attributable to the increased surface area for exchange which in turn brought about a reduction in tissue hypoxia. Taken together cilostazol appears to produce a protective effect against the ischemic-reperfusion injury.

Hydrogen Gas Inhalation Attenuates Endothelial Glycocalyx Damage and Stabilizes Hemodynamics in a Rat Hemorrhagic Shock Model.

BACKGROUND: Hydrogen gas (H2) inhalation during hemorrhage stabilizes post-resuscitation hemodynamics, improving short-term survival in a rat hemorrhagic shock and resuscitation (HS/R) model. However, the underlying molecular mechanism of H2 in HS/R is unclear. Endothelial glycocalyx (EG) damage causes hemodynamic failure associated with HS/R. In this study, we tested the hypothesis that H2 alleviates oxidative stress by suppressing xanthine oxidoreductase (XOR) and/or preventing tumor necrosis factor-alfa (TNF-α)-mediated syndecan-1 shedding during EG damage. METHODS: HS/R was induced in rats by reducing mean arterial pressure (MAP) to 35 mm Hg for 60 min followed by resuscitation. Rats inhaled oxygen or H2 + oxygen after achieving shock either in the presence or absence of an XOR inhibitor (XOR-I) for both the groups. In a second test, rats received oxygen alone or antitumor necrosis factor (TNF)-α monoclonal antibody with oxygen or H2. Two hours after resuscitation, XOR activity, purine metabolites, cytokines, syndecan-1 were measured and survival rates were assessed 6 h after resuscitation. RESULTS: H2 and XOR-I both suppressed MAP reduction and improved survival rates. H2 did not affect XOR activity and the therapeutic effects of XOR-I and H2 were additive. H2 suppressed plasma TNF-α and syndecan-1 expression; however, no additional H2 therapeutic effect was observed in the presence of anti-TNF-α monoclonal antibody. CONCLUSIONS: H2 inhalation after shock stabilized hemodynamics and improved survival rates in an HS/R model independent of XOR. The therapeutic action of H2 was partially mediated by inhibition of TNF-α-dependent syndecan-1 shedding.

Preclinical evaluation of heat-denatured [18F]FDG-labeled red blood cells for detecting splenic tissues with PET in rats.

INTRODUCTION: Heat-denatured 99mTc-labeled red blood cells (RBCs) are used for detecting splenic tissues with scintigraphy. The present study aimed to evaluate the feasibility of using heat-denatured [18F]fluorodeoxyglucose ([18F]FDG)-labeled RBCs in detecting splenic tissues using positron emission tomography (PET) in rats. METHODS: RBCs were washed with phosphate buffered saline, labeled with [18F]FDG at 38°C, and heat-denatured at 50°C for 15 min. In vitro stability was assessed by measuring extracellular radioactivity during the 0-180 min incubation at 37°C. Thin layer chromatography (TLC) of the extracellular fluid was performed. The autologous RBCs were intravenously injected in four rats and PET scanning was simultaneously performed for 30 min. Time-activity curves of several organs, including the spleen, were analyzed on the PET images. RESULTS: Labeling efficiency was 92%. Low levels of radioactivity were released from the labeled RBCs for 180 min. TLC revealed that 80% of the released radioactivity was due to [18F]FDG-6-phosphate. Whole body images showed strong uptake of heat-denatured [18F]FDG-labeled RBCs in the spleen soon after injection in all four rats. Time-activity curves revealed that the splenic uptake continued to increase for 30 min and the amount of radioactivity in the other organs, except the urinary bladder, decreased after the initial surge. CONCLUSIONS: Heat-denatured [18F]FDG-labeled RBCs are suitable spleen-specific agents for PET. This method is clinically relevant as an alternative for heat-denatured 99mTc-labeled RBC scintigraphy.

Neuroprotective Role of Astroglia in Parkinson Disease by Reducing Oxidative Stress Through Dopamine-Induced Activation of Pentose-Phosphate Pathway.

Oxidative stress plays an important role in the onset and progression of Parkinson disease. Although released dopamine at the synaptic terminal is mostly reabsorbed by dopaminergic neurons, some dopamine is presumably taken up by astroglia. This study examined the dopamine-induced astroglial protective function through the activation of the pentose-phosphate pathway (PPP) to reduce reactive oxygen species (ROS). In vitro experiments were performed using striatal neurons and cortical or striatal astroglia prepared from Sprague-Dawley rats or C57BL/6 mice. The rates of glucose phosphorylation in astroglia were evaluated using the [14C]deoxyglucose method. PPP activity was measured using [1-14C]glucose and [6-14C]glucose after acute (60 min) or chronic (15 hr) exposure to dopamine. ROS production was measured using 2',7'-dichlorodihydrofluorescein diacetate. The involvement of the Kelch-like ECH-associated protein 1 (Keap1) or nuclear factor-erythroid-2-related factor 2 (Nrf2) system was evaluated using Nrf2 gene knockout mice, immunohistochemistry, and quantitative reverse transcription polymerase chain reaction analysis for heme oxygenase-1. Acute exposure to dopamine elicited increases in astroglial glucose consumption with lactate release. PPP activity in astroglia was robustly enhanced independently of Na+-dependent monoamine transporters. In contrast, chronic exposure to dopamine induced moderate increases in PPP activity via the Keap1/Nrf2 system. ROS production from dopamine increased gradually over 12 hr. Dopamine induced neuronal cell damage that was prevented by coculturing with astroglia but not with Nrf2-deficient astroglia. Dopamine-enhanced astroglial PPP activity in both acute and chronic manners may possibly reduce neuronal oxidative stress.

Carbon monoxide from heme oxygenase-2 Is a tonic regulator against NO-dependent vasodilatation in the adult rat cerebral microcirculation.

Although the brain generates NO and carbon monoxide (CO), it is unknown how these gases and their enzyme systems interact with each other to regulate cerebrovascular function. We examined whether CO produced by heme oxygenase (HO) modulates generation and action of constitutive NO in the rat pial microcirculation. Immunohistochemical analyses indicated that HO-2 occurred in neurons and arachnoid trabecular cells, where NO synthase 1 (NOS1) was detectable, and also in vascular endothelium-expressing NOS3, suggesting colocalization of CO- and NO-generating sites. Intravital microscopy using a closed cranial window preparation revealed that blockade of the HO activity by zinc protoporphyrin IX significantly dilates arterioles. This vasodilatation depended on local NOS activities and was abolished by CO supplementation, suggesting that the gas derived from HO-2 tonically regulates NO-mediated vasodilatory response. Bioimaging of NO by laser-confocal microfluorography of diaminofluorescein indicated detectable amounts of NO at the microvascular wall, the subdural mesothelial cells, and arachnoid trabecular cells, which express NOS in and around the pial microvasculature. On CO inhibition by the HO inhibitor, regional NO formation was augmented in these cells. Such a pattern of accelerated NO formation depended on NOS activities and was again attenuated by the local CO supplementation. Studies using cultured porcine aortic endothelial cells suggested that the inhibitory action of CO on NOS could result from the photo-reversible gas binding to the prosthetic heme. Collectively, CO derived from HO-2 appears to serve as a tonic vasoregulator antagonizing NO-mediated vasodilatation in the rat cerebral microcirculation.

18F-FDG-labeled red blood cell PET for blood-pool imaging: preclinical evaluation in rats.

BACKGROUND: Red blood cells (RBCs) labeled with single-photon emitters have been clinically used for blood-pool imaging. Although some PET tracers have been introduced for blood-pool imaging, they have not yet been widely used. The present study investigated the feasibility of labeling RBCs with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG) for blood-pool imaging with PET. RBCs isolated from venous blood of rats were washed with glucose-free phosphate-buffered saline and labeled with 18F-FDG. To optimize labeling efficiency, the effects of glucose deprivation time and incubation (labeling) time with 18F-FDG were investigated. Post-labeling stability was assessed by calculating the release fraction of radioactivity and identifying the chemical forms of 18F in the released and intracellular components of 18F-FDG-labeled RBCs incubated in plasma. Just after intravenous injection of the optimized autologous 18F-FDG-labeled RBCs, dynamic PET scans were performed to evaluate in vivo imaging in normal rats and intraabdominal bleeding models (temporary and persistent bleeding). RESULTS: The optimal durations of glucose deprivation and incubation (labeling) with 18F-FDG were 60 and 30 min, respectively. As low as 10% of 18F was released as the form of 18F-FDG from 18F-FDG-labeled RBCs after a 60-min incubation. Dynamic PET images of normal rats showed strong persistence in the cardiovascular system for at least 120 min. In the intraabdominal bleeding models, 18F-FDG-labeled RBC PET visualized the extravascular blood clearly and revealed the dynamic changes of the extravascular radioactivity in the temporary and persistent bleeding. CONCLUSIONS: RBCs can be effectively labeled with 18F-FDG and used for blood-pool imaging with PET in rats.

Nonendothelial source of nitric oxide in arterioles but not in venules: alternative source revealed in vivo by diaminofluorescein microfluorography.

This study aimed to examine topographic distribution of microvascular NO generation in vivo. To this end, nitrosonium ion (NO+)-sensitive diaminofluorescein diacetate was superfused continuously on the rat mesentery and the fluorescence was visualized in the microvessels through laser confocal microfluorography. Two major sites exhibited a time-dependent elevation of the fluorescence: microvascular endothelia and mast cells. As judged by the fluorescence sensitivity to local application of different inhibitors of NO synthase (NOS), NO availability in arteriolar endothelium and mast cells appeared to be maintained mainly by NOS1, whereas that in venular endothelium greatly depends on NOS3. In venules, the magnitude of inhibitory responses elicited by the inhibitors was positively correlated with the density of leukocyte adhesion. NOS inhibitors significantly reduced, but did not eliminate, the NO+-associated fluorescence in arterioles, capillaries, and venules, suggesting alternative sources of NO in circulation for these microvessels. Immunohistochemistry for NOS isozymes revealed that NOS1 occurred not only in nerve fibers innervated to arterioles but also abundantly in mast cells. Laser flow cytometry of peritoneal cells in vitro revealed abundant expression of NOS1 in mast cells. Interestingly, NOS3 occurred in endothelia of capillaries and venules but not in those of distal arterioles with comparable diameters. These results suggest that the arterioles receive NO from nonendothelial origins involving NOS1 present in nerve terminals and mast cells, whereas venules depend on the endothelial NOS as a major source. Furthermore, nonenzymatic sources of NO from circulating reservoirs constitute a notable fraction throughout different classes of microvessels. The full text of this article is available at http://www.circresaha.org.

Visualization of in vivo metabolic flows reveals accelerated utilization of glucose and lactate in penumbra of ischemic heart.

Acute ischemia produces dynamic changes in labile metabolites. To capture snapshots of such acute metabolic changes, we utilized focused microwave treatment to fix metabolic flow in vivo in hearts of mice 10 min after ligation of the left anterior descending artery. The left ventricle was subdivided into short-axis serial slices and the metabolites were analyzed by capillary electrophoresis mass spectrometry and matrix-assisted laser desorption/ionization imaging mass spectrometry. These techniques allowed us to determine the fate of exogenously administered (13)C6-glucose and (13)C3-lactate. The penumbra regions, which are adjacent to the ischemic core, exhibited the greatest adenine nucleotide energy charge and an adenosine overflow extending from the ischemic core, which can cause ischemic hyperemia. Imaging analysis of metabolic pathway flows revealed that the penumbra executes accelerated glucose oxidation, with remaining lactate utilization for tricarboxylic acid cycle for energy compensation, suggesting unexpected metabolic interplays of the penumbra with the ischemic core and normoxic regions.

Cortical microcirculatory disturbance in the super acute phase of subarachnoid hemorrhage - In vivo analysis using two-photon laser scanning microscopy.

OBJECTIVE: Subarachnoid hemorrhage (SAH) causes cerebral ischemia and drastically worsens the clinical status at onset. However, the arterial flow is surprisingly well maintained on the cerebral surface. We investigated cortical microcirculatory changes in the super acute phase of SAH using two-photon laser scanning microscopy (TPLSM). METHODS: SAH was induced at the skull base in 10 mice using a prone endovascular perforation model. Before SAH, and 1, 2, 5, 10, 20, 30 and 60min after SAH, the cortical microcirculation was observed with TPLSM through a cranial window. Diameters of penetrating and precapillary arterioles were measured and red blood cell (RBC) velocities in precapillary arterioles were analyzed using a line-scan method after administration of Q-dot 655 nanocrystals. RESULTS: One minute after SAH, RBC velocity and flow in precapillary arterioles drastically decreased to <20% of the pre-SAH values, while penetrating and precapillary arterioles dilated significantly. Subsequently, the arterioles either dilated or constricted inconsistently for 60min with continual decreases in RBC velocity and flow in the arterioles, suggesting neurovascular dysfunction. CONCLUSION: SAH caused sudden worsening of the cortical arteriolar velocity and flow at onset. The neurovascular unit cannot function sufficiently to maintain cortical microcirculatory flow in the super acute phase of SAH.

Cystathionine ß-synthase and PGRMC1 as CO sensors.

Heme oxygenase (HO) is a mono-oxygenase utilizing heme and molecular oxygen (O2) as substrates to generate biliverdin-IXα and carbon monoxide (CO). HO-1 is inducible under stress conditions, while HO-2 is constitutive. A balance between heme and CO was shown to regulate cell death and survival in many experimental models. However, direct molecular targets to which CO binds to regulate cellular functions remained to be fully examined. We have revealed novel roles of CO-responsive proteins, cystathionine ß-synthase (CBS) and progesterone receptor membrane component 1 (PGRMC1), in regulating cellular functions. CBS possesses a prosthetic heme that allows CO binding to inhibit the enzyme activity and to regulate H2S generation and/or protein arginine methylation. On the other hand, in response to heme accumulation in cells, PGRMC1 forms a stable dimer through stacking interactions of two protruding heme molecules. Heme-mediated PGRMC1 dimerization is necessary to interact with EGF receptor and cytochromes P450 that determine cell proliferation and xenobiotic metabolism. Furthermore, CO interferes with PGRMC1 dimerization by dissociating the heme stacking, and thus results in modulation of cell responses. This article reviews the intriguing functions of these two proteins in response to inducible and constitutive levels of CO with their pathophysiological implications.

Epidermal cell turnover across tight junctions based on Kelvin's tetrakaidecahedron cell shape.

In multicellular organisms, cells adopt various shapes, from flattened sheets of endothelium to dendritic neurons, that allow the cells to function effectively. Here, we elucidated the unique shape of cells in the cornified stratified epithelia of the mammalian epidermis that allows them to achieve homeostasis of the tight junction (TJ) barrier. Using intimate in vivo 3D imaging, we found that the basic shape of TJ-bearing cells is a flattened Kelvin's tetrakaidecahedron (f-TKD), an optimal shape for filling space. In vivo live imaging further elucidated the dynamic replacement of TJs on the edges of f-TKD cells that enables the TJ-bearing cells to translocate across the TJ barrier. We propose a spatiotemporal orchestration model of f-TKD cell turnover, where in the classic context of 'form follows function', cell shape provides a fundamental basis for the barrier homeostasis and physical strength of cornified stratified epithelia.