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.

A general anaesthetic propofol inhibits aquaporin-4 in the presence of Zn²âº.

AQP4 (aquaporin-4), a water channel protein that is predominantly expressed in astrocyte end-feet, plays an important role in the brain oedema formation, and is thereby considered to be a potential therapeutic target. Using a stopped-flow analysis, we showed that propofol (2,6-diisopropylphenol), a general anaesthetic drug, profoundly inhibited the osmotic water permeability of AQP4 proteoliposomes in the presence of Zn²âº. This propofol inhibition was not observed in AQP1, suggesting the specificity for AQP4. In addition, the inhibitory effects of propofol could be reversed by the removal of Zn²âº. Other lipid membrane fluidizers also similarly inhibited AQP4, suggesting that the modulation of protein-lipid interactions plays an essential role in the propofol-induced inhibition of AQP4. Accordingly, we used Blue native PAGE and showed that the profound inhibition caused by propofol in the presence of Zn²âº is coupled with the reversible clustering of AQP4 tetramers. Site-directed mutagenesis identified that Cys²5³, located at the membrane interface connecting to the C-terminal tail, is responsible for Zn²âº-mediated propofol inhibition. Overall, we discovered that propofol specifically and reversibly inhibits AQP4 through the interaction between Zn²âº and Cys²5³. The findings provide new insight into the functional regulation of AQP4 and may facilitate the identification of novel AQP4-specific inhibitors.

Validation of the Index for Facial Angiofibromas: Data analysis from a randomized controlled trial of sirolimus gel treatment in patients with tuberous sclerosis complex.

The Index for Facial Angiofibromas (IFA), a novel scoring system for angiofibromas, has been validated in patients with tuberous sclerosis complex (TSC). The objective of this analysis was to further validate the IFA using data from a clinical trial of topical sirolimus in patients with TSC. This was an analysis of photographs from a Phase III trial conducted in Japan (NCT02635789). Patients (n = 62) were randomized 1:1 to receive sirolimus or placebo gel for 12 weeks. Changes in angiofibromas were independently assessed using the primary composite endpoint, the Facial Angiofibroma Severity Index (FASI), and the IFA. Thresholds for a clinically meaningful change in IFA score were evaluated using receiver operating characteristic (ROC) analysis. The IFA scores had good-to-excellent inter-assessor reliability, very high intra-assessor reliability, and could be used to evaluate the distribution of disease severity at baseline. High correlations were observed between the categorized change from baseline in IFA scores and the primary composite endpoint (Kendall's coefficient of concordance, W = 0.8655, p < 0.0001), and between the change from baseline in IFA and FASI scores (Kendall's coefficient of concordance, W = 0.745, p < 0.0001). By ROC analysis, an optimal IFA cut-off point of 1.667 was determined to distinguish patients with markedly improved or improved angiofibromas from those with slightly improved or unchanged angiofibromas (area under the curve 0.937) as determined by the primary composite endpoint. The IFA score is potentially clinically useful because of its high validity and reliability. A decrease in score from baseline of ≥1.667 may be considered clinically meaningful.

Aquaporin AqpZ is involved in cell volume regulation and sensitivity to osmotic stress in Synechocystis sp. strain PCC 6803.

The moderately halotolerant cyanobacterium Synechocystis sp. strain PCC 6803 contains a plasma membrane aquaporin, AqpZ. We previously reported that AqpZ plays a role in glucose metabolism under photomixotrophic growth conditions, suggesting involvement of AqpZ in cytosolic osmolarity homeostasis. To further elucidate the physiological role of AqpZ, we have studied its gene expression profile and its function in Synechocystis. The expression level of aqpZ was regulated by the circadian clock. AqpZ activity was insensitive to mercury in Xenopus oocytes and in Synechocystis, indicating that the AqpZ can be categorized as a mercury-insensitive aquaporin. Stopped-flow light-scattering spectrophotometry showed that addition of sorbitol and NaCl led to a slower decrease in cell volume of the Synechocystis ΔaqpZ strain than the wild type. The ΔaqpZ cells were more tolerant to hyperosmotic shock by sorbitol than the wild type. Consistent with this, recovery of oxygen evolution after a hyperosmotic shock by sorbitol was faster in the ΔaqpZ strain than in the wild type. In contrast, NaCl stress had only a small effect on oxygen evolution. The amount of AqpZ protein remained unchanged by the addition of sorbitol but decreased after addition of NaCl. This decrease is likely to be a mechanism to alleviate the effects of high salinity on the cells. Our results indicate that Synechocystis AqpZ functions as a water transport system that responds to daily oscillations of intracellular osmolarity.

Rapid and reversible inhibition of aquaporin-4 by zinc.

Aquaporin-4 (AQP4) is the predominant water channel in the brain. Although AQP4 plays an important role in brain water homeostasis, the molecular mechanisms of AQP4 regulation are not fully understood. In this report, we show how Zn(2+) rapidly and reversibly decreases the water permeability of AQP4 when it is reconstituted into proteoliposomes. Mutagenesis analysis identified Cys178, located in cytoplasmic loop D, as a target residue of ZnCl(2) inhibition. Moreover, treatment with diamide enhanced the inhibitory effects of ZnCl(2). These results suggest that the water permeability of AQP4 may be regulated by dynamic changes in intracellular Zn(2+) concentration linked to the cellular redox state.

Mercury chloride decreases the water permeability of aquaporin-4-reconstituted proteoliposomes.

BACKGROUND INFORMATION: Mercurials inhibit AQPs (aquaporins), and site-directed mutagenesis has identified Cys(189) as a site of the mercurial inhibition of AQP1. On the other hand, AQP4 has been considered to be a mercury-insensitive water channel because it does not have the reactive cysteine residue corresponding to Cys(189) of AQP1. Indeed, the osmotic water permeability (P(f)) of AQP4 expressed in various types of cells, including Xenopus oocytes, is not inhibited by HgCl2. To examine the direct effects of mercurials on AQP4 in a proteoliposome reconstitution system, His-tagged rAQP4 [corrected] (rat AQP4) M23 was expressed in Saccharomyces cerevisiae, purified with an Ni2+-nitrilotriacetate affinity column, and reconstituted into liposomes with the dilution method. RESULTS: The water permeability of AQP4 proteoliposomes with or without HgCl2 was measured with a stopped-flow apparatus. Surprisingly, the P(f) of AQP4 proteoliposomes was significantly decreased by 5 microM HgCl2 within 30 s, and this effect was completely reversed by 2-mercaptoethanol. The dose- and time-dependent inhibitory effects of Hg2+ suggest that the sensitivity to mercury of AQP4 is different from that of AQP1. Site-directed mutagenesis of six cysteine residues of AQP4 demonstrated that Cys(178), which is located at loop D facing the intracellular side, is a target responding to Hg2+. We confirmed that AQP4 is reconstituted into liposome in a bidirectional orientation. CONCLUSIONS: Our results suggest that mercury inhibits the P(f) of AQP4 by mechanisms different from those for AQP1 and that AQP4 may be gated by modification of a cysteine residue in cytoplasmic loop D.

Four different clones of mouse anti-acetyllysine monoclonal antibodies having different recognition properties share a common immunoglobulin framework structure.

By employing two different immunogens and two different antibody-screening strategies, we established four mouse hybridoma clones producing monoclonal antibodies against N epsilon -acetyllysine. Three different protocols were used in this study; i.e., mice were (1) immunized with an N epsilon -acetyllysine-containing peptide, Gly-Lys(Ac)- epsilon -aminocaproic acid (Aca)-Cys, conjugated to KLH, and the hybridoma clones were screened for their reactivity to a histone H3 peptide containing five acetyllysines; (2) immunized as in "1" and screened with chemically acetylated bovine serum albumin (BSA); (3) immunized with chemically acetylated keyhole limpet hemocyanin (KLH) and screened with chemically acetylated BSA. Antibodies produced by the four different hybridomas established here all reacted with acetyllysine residues, but their reactivity was not the same when evaluated with enzyme-linked immunosorbent assay (ELISA), Western blotting, and resonant mirror sensor analyses. Among the three protocols examined, protocol "3" was especially useful to obtain hybridomas producing anti-N epsilon -acetyllysine antibodies that could detect not only the acetylated histones but also other acetylated proteins. By cloning and sequencing the cDNAs encoding the variable regions of the antibodies, we found that their framework sequences were almost the same, which suggests that some framework amino acids in addition to their complementarity determining regions (CDRs) directly contribute to their recognition function.

Characterization of the role of a mechanosensitive channel in osmotic down shock adaptation in Synechocystis sp PCC 6803.

Synechocystis sp strain PCC 6803 contains one gene encoding a putative large conductance mechanosensitive channel homolog [named SyMscL (slr0875)]. However, it is unclear whether SyMscL contributes to the adaptation to hypoosmotic stress in Synechocystis. Here we report the in vivo characteristics of SyMscL. SyMscL was mainly expressed in the plasma membrane of Synechocystis. Cell volume monitoring using stopped-flow spectrophotometry showed that ΔsymscL cells swelled more rapidly than wild-type cells under hypoosmotic stress conditions. Expression of symscL was under circadian control, and its peak corresponded to the beginning of subjective night. These results indicate that SyMscL functioned as one component of the osmotic homeostatic regulatory system of the cell coordinating the response of Synechocystis to daily metabolic osmotic fluctuations and environmental changes.

Gas biology: tiny molecules controlling metabolic systems.

It has been recognized that gaseous molecules and their signaling cascades play a vital role in alterations of metabolic systems in physiologic and pathologic conditions. Contrary to this awareness, detailed mechanisms whereby gases exert their actions, in particular in vivo, have been unclear because of several reasons. Gaseous signaling involves diverse reactions with metal centers of metalloproteins and thiol modification of cysteine residues of proteins. Both the multiplicity of gas targets and the technical limitations in accessing local gas concentrations make dissection of exact actions of any gas mediator a challenge. However, a series of advanced technologies now offer ways to explore gas-responsive regulatory processes in vivo. Imaging mass spectrometry combined with quantitative metabolomics by capillary-electrophoresis/mass spectrometry reveals spatio-temporal profiles of many metabolites. Comparing the metabolic footprinting of murine samples with a targeted deletion of a specific gas-producing enzyme makes it possible to determine sites of actions of the gas. In this review, we intend to elaborate on the ideas how small gaseous molecules interact with metabolic systems to control organ functions such as cerebral vascular tone and energy metabolism in vivo.