Carbon dioxide inhibits UVB-induced inflammatory response by activating the proton-sensing receptor, GPR65, in human keratinocytes.

Carbon dioxide (CO2) is the predominant gas molecule emitted during aerobic respiration. Although CO2 can improve blood circulation in the skin via its vasodilatory effects, its effects on skin inflammation remain unclear. The present study aimed to examine the anti-inflammatory effects of CO2 in human keratinocytes and skin. Keratinocytes were cultured under 15% CO2, irradiated with ultraviolet B (UVB), and their inflammatory cytokine production was analyzed. Using multiphoton laser microscopy, the effect of CO2 on pH was observed by loading a three-dimensional (3D)-cultured epidermis with a high-CO2 concentration formulation. Finally, the effect of CO2 on UVB-induced erythema was confirmed. CO2 suppressed the UVB-induced production of tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6) in keratinocytes and the 3D epidermis. Correcting medium acidification with NaOH inhibited the CO2-induced suppression of TNFα and IL-6 expression in keratinocytes. Moreover, the knockdown of H+-sensing G protein-coupled receptor 65 inhibited the CO2-induced suppression of inflammatory cytokine expression and NF-κB activation and reduced CO2-induced cyclic adenosine monophosphate production. Furthermore, the high-CO2 concentration formulation suppressed UVB-induced erythema in human skin. Hence, CO2 suppresses skin inflammation and can be employed as a potential therapeutic agent in restoring skin immune homeostasis.

Carbon dioxide ameliorates reduced desquamation in dry scaly skin via protease activation.

OBJECTIVE: Scaling, a phenomenon showing an abnormal detachment of the stratum corneum (SC) owing to desquamation dysfunction, is commonly observed in various skin diseases or xerotic skin due to ageing and low humidity. Therefore, it is considered that ameliorating the disturbed desquamatory process of the SC leads to improvement in scaling. Carbon dioxide (CO2 ) is known to be good for some skin diseases; however, the effect of CO2 on scaling and its mechanism are not sufficiently clear. We aimed to elucidate the effect of transepidermal application of CO2 on scaling and its mechanism of action. METHODS: Twenty healthy men with mild scaling on the cheeks were recruited for a double-blind, placebo-controlled, split-face study. They applied the formulation containing CO2 twice daily for 1 week. After the study, the SC was collected by tape stripping to analyse desquamatory protease activities and degradation of extracellular corneodesmosomes. Furthermore, the contribution of pH to proteolysis of the corneodesmosome by CO2 was evaluated using three-dimensional (3D) cultured epidermal models. RESULTS: The spectroscopic absorbance of tape strips, used as scaling indicators, was decreased, concomitantly with the amelioration of incomplete degradation of desmoglein-1, one of the main corneodesmosomal proteins, and activation of trypsin-like protease in the SC by transepidermal application of CO2 . Experiments using 3D cultured epidermis showed that pH in the epidermal tissue was lowered by CO2 , whereas a pH change was not observed with the application of the formulation containing hydrochloric acid, which was added to equalize the pH to that of the CO2 formulation. CONCLUSION: The transcutaneous application of CO2 ameliorates reduced desquamatory process in xerotic skin, with concomitant mild acidification of the SC, thereby leading to improvement in scaling. Thus, CO2 may have an advantage of efficiently and safely counteracting scaling of various skin disorders.

OBJECTIF: La desquamation, phénomène caractérisé par un détachement anormal de la couche cornée (CC) dû à un dysfonctionnement de l'épiderme, est fréquemment observée dans diverses maladies de la peau ou en cas de xérose résultant du vieillissement et de la faible humidité. Par conséquent, il est considéré que le soulagement du trouble à l'origine du processus desquamant de la CC réduit la desquamation. Le dioxyde de carbone (CO2) est réputé bénéfique pour certaines maladies de la peau. Cependant, l'effet du CO2 sur la desquamation et son mécanisme ne sont pas suffisamment clairs. Nous avons cherché à élucider l'effet de l'application transépidermique du CO2 sur la desquamation et son mécanisme d'action. MÉTHODES: Vingt hommes en bonne santé, présentant une légère desquamation sur les joues, ont été recrutés dans le cadre d'une étude en double aveugle, contrôlée par un placebo, en hémiface. Ils ont appliqué la formule contenant du CO2 deux fois par jour, pendant 1 semaine. Après l'étude, la CC a été recueillie par décollement de ruban adhésif, en vue de l'analyse des activités de la protéase desquamante et de la dégradation des cornéodesmosomes extracellulaires. En outre, la contribution du pH à la protéolyse du cornéodesmosome par le CO2 , a été évaluée à l'aide de modèles d'épidermes cultivés tridimensionnels (3D). RÉSULTATS: L'absorbance spectroscopique des bandelettes de ruban adhésif, utilisées comme indicateurs de desquamation, a été réduite, concomitamment avec la baisse de la dégradation incomplète de la desmogléine-1, l'une des principales protéines des cornéodesmosomes, et l'activation de la trypsine dans la CC par application transépidermique de CO2 . Des expériences menées sur un épiderme cultivé en 3D ont montré que le pH dans le tissu épidermique était réduit par le CO2 , tandis qu'aucun changement de pH n'a été observé avec l'application de la formule contenant de l'acide chlorhydrique, ajoutée pour que le pH soit identique à celui de la formule contenant du CO2 . CONCLUSION: L'application transcutanée de CO2 améliore la réduction du processus desquamant de la peau atteinte de xérose, avec une légère acidification concomitante de la CC, entraînant ainsi une réduction de la desquamation. Par conséquent, le CO2 peut présenter l'avantage de contrer la desquamation de manière efficace et sûre, pour diverses affections cutanées.

Type I neuregulin1α is a novel local mediator to suppress hepatic gluconeogenesis in mice.

Neuregulin1 is an epidermal growth factor (EGF)-like domain-containing protein that has multiple isoforms and functions as a local mediator in the control of various cellular functions. Here we show that type I isoform of neuregulin1 with an α-type EGF-like domain (Nrg1α) is the major isoform in mouse liver and regulates hepatic glucose production. Forced expression of Nrg1α in mouse liver enhanced systemic glucose disposal and decreased hepatic glucose production with reduced fasting blood glucose levels. Nuclear forkhead box protein O1 (FoxO1) and its downstream targets, PEPCK and G6Pase, were suppressed in liver and isolated hepatocytes by Nrg1α overexpression. In contrast, silencing of Nrg1α enhanced glucose production with increased PEPCK and G6Pase expressions in cAMP/dexamethasone-stimulated hepatocytes. Mechanistically, the recombinant α-type EGF-like domain of NRG1α (rNRG1α) stimulated the ERBB3 signalling pathway in hepatocytes, resulting in decreased nuclear FoxO1 accumulation via activation of both the AKT and ERK pathways. In addition, acute treatment with rNRG1α also suppressed elevation of blood glucose levels after both glucose and pyruvate challenge. Although a liver-specific deletion of Nrg1 gene in mice showed little effect on systemic glucose metabolism, these results suggest that NRG1α have a novel regulatory function in hepatic gluconeogenesis by regulating the ERBB3-AKT/ERK-FoxO1 cascade.

HIF-1α-PDK1 axis-induced active glycolysis plays an essential role in macrophage migratory capacity.

In severely hypoxic condition, HIF-1α-mediated induction of Pdk1 was found to regulate glucose oxidation by preventing the entry of pyruvate into the tricarboxylic cycle. Monocyte-derived macrophages, however, encounter a gradual decrease in oxygen availability during its migration process in inflammatory areas. Here we show that HIF-1α-PDK1-mediated metabolic changes occur in mild hypoxia, where mitochondrial cytochrome c oxidase activity is unimpaired, suggesting a mode of glycolytic reprogramming. In primary macrophages, PKM2, a glycolytic enzyme responsible for glycolytic ATP synthesis localizes in filopodia and lammelipodia, where ATP is rapidly consumed during actin remodelling processes. Remarkably, inhibition of glycolytic reprogramming with dichloroacetate significantly impairs macrophage migration in vitro and in vivo. Furthermore, inhibition of the macrophage HIF-1α-PDK1 axis suppresses systemic inflammation, suggesting a potential therapeutic approach for regulating inflammatory processes. Our findings thus demonstrate that adaptive responses in glucose metabolism contribute to macrophage migratory activity.

WITHDRAWN: Loss of hepatic HIF-1α accelerates lipid accumulation by inhibiting peroxisomal fatty acid oxidation in nonalcoholic fatty liver disease.

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