MicroRNA-26a in respiratory diseases: mechanisms and therapeutic potential.

MicroRNAs (miRNAs) are short, non-coding single-stranded RNA molecules approximately 22 nucleotides in length, intricately involved in post-transcriptional gene expression regulation. Over recent years, researchers have focused keenly on miRNAs, delving into their mechanisms in various diseases such as cancers. Among these, miR-26a emerges as a pivotal player in respiratory ailments such as pneumonia, idiopathic pulmonary fibrosis, lung cancer, asthma, and chronic obstructive pulmonary disease. Studies have underscored the significance of miR-26a in the pathogenesis and progression of respiratory diseases, positioning it as a promising therapeutic target. Nevertheless, several challenges persist in devising medical strategies for clinical trials involving miR-26a. In this review, we summarize the regulatory role and significance of miR-26a in respiratory diseases, and we analyze and elucidate the challenges related to miR-26a druggability, encompassing issues such as the efficiency of miR-26a, delivery, RNA modification, off-target effects, and the envisioned therapeutic potential of miR-26a in clinical settings.

Advanced nanoparticles that can target therapy and reverse drug resistance may be the dawn of leukemia treatment: A bibliometrics study.

With the development of nanomedicine, more and more nanoparticles are used in the diagnosis and treatment of leukemia. This study aimed to identify author, country, institutional, and journal collaborations and their impacts, assess the knowledge base, identify existing trends, and uncover emerging topics related to leukemia research. 1825 Articles and reviews were obtained from the WoSCC and analyzed by Citespace and Vosviewer. INTERNATIONAL JOURNAL OF NANOMEDICINE is the journal with the highest output. The contribution of FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY is also noteworthy. The three main aspects of research in Nanoparticles-leukemia-related fields included nanoparticles for the diagnosis and treatment of leukemia, related to the type and treatment of leukemia, the specific molecular mechanism, and existing problems of the application of nanoparticles in leukemia. In the future, synthesize nano-drugs that have targeted therapy and chemotherapy resistance according to the mechanism, which may be the dawn of the solution to leukemia. This study offers a comprehensive overview of the Nanoparticles-leukemia-related field using bibliometrics and visual methods for the first time, providing a valuable reference for researchers interested in Nanoparticles-leukemia.

Chronic Variable Stress Induces Hepatic Fe(II) Deposition by Up-Regulating ZIP14 Expression via miR-181 Family Pathway in Rats.

It is well-known that hepatic iron dysregulation, which is harmful to health, can be caused by stress. The aim of the study was to evaluate chronic variable stress (CVS) on liver damage, hepatic ferrous iron deposition and its molecular regulatory mechanism in rats. Sprague Dawley rats at seven weeks of age were randomly divided into two groups: a control group (Con) and a CVS group. CVS reduces body weight, but increases the liver-to-body weight ratio. The exposure of rats to CVS increased plasma aspartate aminotransferase (AST), alkaline phosphatase (ALP) and hepatic malondialdehyde (MDA) levels, but decreased glutathione peroxidase (GSH-Px) activity, resulting in liver damage. CVS lowered the total amount of hepatic iron content, but induced hepatic Fe(II) accumulation. CVS up-regulated the expression of transferrin receptor 1 (TFR1) and ZRT/IRT-like protein 14 (ZIP14), but down-regulated ferritin and miR-181 family members. In addition, miR-181 family expression was found to regulate ZIP14 expression in HEK-293T cells by the dual-luciferase reporter system. These results indicate that CVS results in liver damage and induces hepatic Fe(II) accumulation, which is closely associated with the up-regulation of ZIP14 expression via the miR-181 family pathway.

Study of thermotolerant mechanism of Stropharia rugosoannulata under high temperature stress based on the transcriptome sequencing.

Stropharia rugosoannulata is a popular edible mushroom in the world. High temperature seriously affects its yield and quality. In this study, transcriptome sequencing was performed on the mycelia of heat-resistant strains and heat-sensitive strains heat-treated at 38 °C for 0 h and 24 h. The changes of catalase (CAT) activity, superoxide dismutase (SOD) activity and trehalose content in the mycelia under high temperature stress were also measured and analyzed. We find that the differential genes are mainly enriched in the pathways of glycerophospholipid metabolism, starch and sucrose metabolism, protein processing in the endoplasmic reticulum, etc. The expression levels of genes encoding trehalose-6-phosphate phosphatase (TPP), CAT, SOD, etc. are quite different. And these genes' variation range in the thermotolerant strain are higher than that in heat-sensitive strain. The CAT activity and trehalose content of the two strains increase first and then decrease, and the SOD activity increase slowly. The CAT, SOD activity and trehalose content of the thermotolerant strain are higher than those of the heat-sensitive strain. This study will provide a basis for further research on important signal pathways and gene function identification of S. rugosoannulata related to high temperature stress.

Repeated Restraint Stress Enhances Hepatic TFR2 Expression and Induces Hepatic Iron Accumulation in Rats.

Abnormal hepatic iron metabolism is detrimental to health. The objective of this study was to detect repeated restraint stress on liver iron metabolism in rats. Twenty-four male rats aged 7 weeks were randomly divided into 2 groups: control group (Con) and repeated restraint stress group (RS). Rats were subjected to 6 h of daily restraint stress for 14 consecutive days in the repeated restraint stress group. The results showed that repeated restraint stress exposure decreased growth performance including impaired final weight (P = 0.07), reducing average daily gain (P = 0.01), and average daily feed intake (P = 0.00) during the 14-day experimental period. Repeated restraint stress exposure did not affect hemoglobin content and plasma iron parameters except downregulated unsaturated iron-binding capacity (P = 0.04). Repeated restraint stress exposure inhibited liver development (P = 0.03) and induced liver iron accumulation (P = 0.05). In addition, repeated restraint stress downregulated the expression of transferrin (TF) and transferrin receptor 2 (TFR2) at the mRNA level (P < 0.01), but upregulated at the protein level (P = 0.03 for TF; P = 0.00 for TFR2). These results indicated that repeated restraint stress induces hepatic iron accumulation, which is closely related to higher expression of hepatic TFR2 protein in rats.

MiR-20b Down-Regulates Intestinal Ferroportin Expression In Vitro and In Vivo.

Ferroportin (FPN) is the only known cellular iron exporter in mammalian. However, post-transcriptional regulation of intestinal FPN has not yet been completely understood. In this study, bioinformatics algorithms (TargetScan, PicTar, PITA, and miRanda) were applied to predict, screen and obtain microRNA-17 family members (miR-17, miR-20a, miR-20b, and miR-106a) targeting FPN, 'seed sequence' and responding binding sites on the 3'untranslated region (3'UTR) region of FPN. Dual-luciferase reporter assays revealed miRNA-17 family members' mimics decreased the luciferase activity, whereas their inhibitors increased the luciferase activity. Compared with the FPN 3'UTR wild type reporter, co-transfection of a miRNA-17 family members' over-expression plasmids and FPN 3'UTR mutant reporters enhanced the luciferase activity in HCT116 cells. Transfection with miR-20b overexpression plasmid significantly enhanced its expression, and it inhibited endogenous FPN protein expression in Caco-2 cells. Additionally, tail-vein injection of miR-20b resulted in increasing duodenal miR-20b expression, decreasing duodenal FPN protein expression, which was closely related to lower plasma iron level in mice. Taken together, these data suggest that the miR-20b is identified to regulate intestinal FPN expression in vitro and in vivo, which will provide a potential target for intestinal iron exportation.

Identification and Functional Verification of MicroRNA-16 Family Targeting Intestinal Divalent Metal Transporter 1 (DMT1) in vitro and in vivo.

Divalent metal transporter 1 (DMT1) is a key transporter of iron uptake and delivering in human and animals. However, post-transcriptional regulation of DMT1 is poorly understood. In this study, bioinformatic algorithms (TargetScan, PITA, miRanda, and miRDB) were applied to predict, screen, analyze, and obtain microRNA-16 family members (miR-16, miR-195, miR-497, and miR-15b) targeting DMT1, seed sequence and their binding sites within DMT1 3' untranslated region (3' UTR) region. As demonstrated by dual-luciferase reporter assays, luciferase activity of DMT1 3' UTR reporter was impaired/enhanced when microRNA-16 family member over-expression plasmid/its inhibitor was transfected to HCT116 cells. Corroboratively, co-transfection of microRNA-16 family member over-expression plasmid and DMT1 3' UTR mutant reporter repressed the luciferase activity in HCT116 cells. In addition, over-expression microRNA-16 family member augmented its expression and diminished DMT1 protein expression in HCT116 cells. Interestingly, tail vein injection of miR-16 assay revealed reduced plasma iron levels, higher miR-16 expression, and lower DMT1 protein expression in the duodenum of mice. Taken together, we provide evidence that microRNA-16 family (miR-16, miR-195, miR-497, and miR-15b) is confirmed to repress intestinal DMT1 expression in vitro and in vivo, which will give valuable insight into post-transcriptional regulation of DMT1.

Effects of wine-cap Stropharia cultivation on soil nutrients and bacterial communities in forestlands of northern China.

BACKGROUND: Cultivating the wine-cap mushroom (Stropharia rugosoannulata) on forestland has become popular in China. However, the effects of wine-cap Stropharia cultivation on soil nutrients and bacterial communities are poorly understood. METHODS: We employed chemical analyses and high-throughput sequencing to determine the impact of cultivating the wine-cap Stropharia on soil nutrients and bacterial communities of forestland. RESULTS: Cultivation regimes of Stropharia on forestland resulted in consistent increases of soil organic matter (OM) and available phosphorus (AP) content. Among the cultivation regimes, the greatest soil nutrient contents were found in the one-year interval cultivation regime, and the lowest total N and alkaline hydrolysable N contents were observed in the current-year cultivation regime. No significant differences were observed in alpha diversity among all cultivation regimes. Specific soil bacterial groups, such as Acidobacteria, increased in abundance after cultivation of Stropharia rugosoannulata. DISCUSSION: Given the numerous positive effects exerted by OM on soil physical and chemical properties, and the consistent increase in OM content for all cultivation regimes, we suggest that mushroom cultivation is beneficial to forest soil nutrient conditions through increasing OM content. Based on the fact that the one-year interval cultivation regime had the highest soil nutrient content as compared with other cultivation regimes, we recommend this regime for application in farming practice. The spent mushroom compost appeared to be more influential than the hyphae of S. rugosoannulata on the soil nutrients and bacterial communities; however, this requires further study. This research provides insight into understanding the effects of mushroom cultivation on the forest soil ecosystem and suggests a relevant cultivation strategy that reduces its negative impacts.

Long-Term High-Fat Diet Decreases Hepatic Iron Storage Associated with Suppressing TFR2 and ZIP14 Expression in Rats.

High-fat diet-induced obesity is known to disturb hepatic iron metabolism in a time-dependent manner. The mechanism of decreased hepatic iron deposits induced by long-term high-fat diet needs to be further investigated. In this study, 24 6-week-old male Sprague-Dawley rats were given a 16-week high-fat diet and hepatic iron metabolism was examined. High-fat diet feeding considerably decreased hepatic iron contents, enhanced transferrin expression, and reduced the expression of ferritin heavy chain, ferritin light chain, and hepatic iron uptake-related proteins (transferrin receptor 2, TFR2, and ZRT/IRT-like protein 14, ZIP14) in rats. Impaired expression of hepatic TFR2 coincided with DNA hypermethylation on the promoter and repressed expression of transcription factor hepatocyte nuclear factor 4α (HNF4α). miR-181 family expression was markedly increased and verified to regulate Zip14 expression by the dual-luciferase reporter system. Taken together, long-term high-fat diet decreases hepatic iron storage, which is closely linked to inhibition of liver iron transport through the TFR2 and ZIP14-dependent pathway.

Long-Term Dexamethasone Exposure Down-Regulates Hepatic TFR1 and Reduces Liver Iron Concentration in Rats.

Exposure to stress is known to cause hepatic iron dysregulation, but the relationship between prolonged stress and liver iron metabolism is not yet fully understood. Thirty 13-week-old female Sprague-Dawley rats were randomly divided into two groups, as follows: the control group (saline-injection) and the dexamethasone group (Dexamethasone (Dex)-injection 0.1 mg/kg/day). After the 21-day stress trial, the results showed that chronic Dex administration not only impaired serum corticosterone (p = 0.00) and interleukin-6 (IL-6) (p = 0.01) levels, but also decreased white blood cell counts (p = 0.00), and reduced blood lymphocyte counts (p = 0.00). The daily Dex-injection also significantly reduced body weight (p < 0.01) by inhibiting food intake. Consecutive Dex administration resulted in decreased iron intake (p = 0.00), enhanced serum iron levels (p = 0.01), and increased the serum souble transferrin receptor (sTfR) content (p = 0.00) in rats. Meanwhile, long-term Dex exposure down-regulated duodenal cytochrome b (DCYTB) (p = 0.00) and the divalent metal transporter 1 (DMT1) (p = 0.04) protein expression, but up-regulated ferroportin (FPN) protein expression (p = 0.04). Chronic Dex administration reduced liver iron concentration (p = 0.02) in rats. Hepatic transferrin receptor 1 (TFR1) expression was lowered at the protein level (p = 0.03), yet with uncoupled mRNA abundance in Dex-treated rats. Enhanced iron-regulatory protein (IRP)/iron-responsive element (IRE) binding activity was observed, but did not line up with lowered hepatic TFR1 protein expression. This study indicates that long-term Dex exposure reduces liver iron content, which is closely associated with down-regulated hepatic TFR1 protein expression.

Maternal protein restriction depresses the duodenal expression of iron transporters and serum iron level in male weaning piglets.

To investigate the effects of maternal dietary protein restriction on offspring Fe metabolism, twenty-four second-parity Landrace×Yorkshire sows were randomly allocated to standard-protein (SP) and low-protein (LP) groups. The SP sows were fed diets containing 15 and 18 % crude protein throughout pregnancy and lactation, respectively, whereas the LP sows were subjected to 50 % dietary protein restriction. Offspring birth weight was not affected, but the body weight at weaning (P=0·06) and average daily gain (P=0·01) of the female piglets were significantly decreased. Serum Fe level in the LP piglets was markedly decreased at weaning, especially in males (P=0·03). Serum ferritin level (P=0·08) tended to be lower, yet serum transferrin was greatly higher (P=0·01) in male weaning piglets of the LP group. Duodenal expression of the divalent metal transporter 1 (DMT1) and ferroportin (FPN) was surprisingly reduced (P<0·05) at the level of protein, but not at the mRNA level, in male weaning piglets of the LP group. Male weaning piglets born to the LP sows exhibited higher hepatic hepcidin levels (P=0·09), lower hepatic expression of transferrin (P<0·01) and transferrin receptor 1 (P<0·05) at the level of mRNA. However, no significant differences were observed for hepatic Fe storage, ferritin, transferrin and transferrin receptor 1 protein expression in male weaning piglets of the two groups. These results indicate that maternal protein restriction during pregnancy and lactation influences growth of female offspring at weaning, reduces duodenal expression of Fe transporters (DMT1 and FPN) and decreases serum Fe level in male weaning piglets.

Activation of group I metabotropic glutamate receptors regulates the excitability of rat retinal ganglion cells by suppressing Kir and I h.

Group I metabotropic glutamate receptor (mGluR I) activation exerts a slow postsynaptic excitatory effect in the CNS. Here, the issues of whether and how this receptor is involved in regulating retinal ganglion cell (RGC) excitability were investigated in retinal slices using patch-clamp techniques. Under physiological conditions, RGCs displayed spontaneous firing. Extracellular application of LY367385 (10 µM)/MPEP (10 µM), selective mGluR1 and mGluR5 antagonists, respectively, significantly reduced the firing frequency, suggesting that glutamate endogenously released from bipolar cells constantly modulates RGC firing. DHPG (10 µM), an mGluR I agonist, significantly increased the firing and caused depolarization of the cells, which were reversed by LY367385, but not by MPEP, suggesting the involvement of the mGluR1 subtype. Intracellular Ca2+-dependent PI-PLC/PKC and calcium/calmodulin-dependent protein kinase II (CaMKII) signaling pathways mediated the DHPG-induced effects. In the presence of cocktail synaptic blockers (CNQX, D-AP5, bicuculline, and strychnine), which terminated the spontaneous firing in both ON and OFF RGCs, DHPG still induced depolarization and triggered the cells to fire. The DHPG-induced depolarization could not be blocked by TTX. In contrast, Ba2+, an inwardly rectifying potassium channel (Kir) blocker, and Cs+ and ZD7288, hyperpolarization-activated cation channel (I h) blockers, mimicked the effect of DHPG. Furthermore, in the presence of Ba2+/ZD7288, DHPG did not show further effects. Moreover, Kir and I h currents could be recorded in RGCs, and extracellular application of DHPG indeed suppressed these currents. Our results suggest that activation of mGluR I regulates the excitability of rat RGCs by inhibiting Kir and I h.

Decreased miR-144 expression as a non-invasive biomarker for acute myeloid leukemia patients.

MicroRNAs are found to be stable in blood and they demonstrated tissue specific expression patterns. Thus, they may be used as potential non-invasive biomarkers of specific cancers. In the current study, we mainly focused on miR-144, which has never been studied in acute myeloid leukemia (AML). The expression of miR-144 was explored in the bone marrow and peripheral blood of AML patients and healthy control. The correlation between peripheral blood miR-144 level and key clinical parameters, including overall survival and prognostic value, was further explored. We showed that miR-144 was markedly reduced in both the peripheral blood and bone marrow of AML patients compared with healthy controls. Further study revealed that there is a significant correlation between peripheral blood miR-144 level and FAB classification (p=0.0023) and cytogenetics (p=0.001). More importantly, a lower expression of peripheral blood miR-144 level was found to be positively correlated with poorer overall survival rate. In summary, peripheral blood miR-144 may be utilized as a potential novel non-invasive biomarker for AML screening.

Downregulation of miR-150 Expression by DNA Hypermethylation Is Associated with High 2-Hydroxy-(4-methylthio)butanoic Acid-Induced Hepatic Cholesterol Accumulation in Nursery Piglets.

Excess 2-hydroxy-(4-methylthio)butanoic acid (HMB) supplementation induces hyperhomocysteinemia, which contributes to hepatic cholesterol accumulation. However, it is unclear whether and how high levels of HMB break hepatic cholesterol homeostasis in nursery piglets. In this study, HMB oversupplementation suppressed food intake and decreased body weight in nursery piglets. Hyperhomocysteinemia and higher hepatic cholesterol accumulation were observed in HMB groups. Accordingly, HMB significantly increased the protein content of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and glycine N-methyltransferase (GNMT) but decreased that of acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1). Significant downregulation of miR-150, miR-181d-5p, and miR-296-3p targeting the 3'-untranslated regions (UTRs) of GNMT and HMGCR was detected in the liver of HMB-treated piglets, and their functional validation was confirmed by dual-luciferase reporter assay. Furthermore, hypermethylation of miR-150 promoter was detected in association with suppressed miR-150 expression in the livers of HMB-treated piglets. This study indicated a new mechanism of hepatic cholesterol unhomeostasis by dietary methyl donor supplementation.

Acetate functions as an epigenetic metabolite to promote lipid synthesis under hypoxia.

Besides the conventional carbon sources, acetyl-CoA has recently been shown to be generated from acetate in various types of cancers, where it promotes lipid synthesis and tumour growth. The underlying mechanism, however, remains largely unknown. We find that acetate induces a hyperacetylated state of histone H3 in hypoxic cells. Acetate predominately activates lipogenic genes ACACA and FASN expression by increasing H3K9, H3K27 and H3K56 acetylation levels at their promoter regions, thus enhancing de novo lipid synthesis, which combines with its function as the metabolic precursor for fatty acid synthesis. Acetyl-CoA synthetases (ACSS1, ACSS2) are involved in this acetate-mediated epigenetic regulation. More importantly, human hepatocellular carcinoma with high ACSS1/2 expression exhibit increased histone H3 acetylation and FASN expression. Taken together, this study demonstrates that acetate, in addition to its ability to induce fatty acid synthesis as an immediate metabolic precursor, also functions as an epigenetic metabolite to promote cancer cell survival under hypoxic stress.

Translational Control Protein 80 Stimulates IRES-Mediated Translation of p53 mRNA in Response to DNA Damage.

Synthesis of the p53 tumor suppressor increases following DNA damage. This increase and subsequent activation of p53 are essential for the protection of normal cells against tumorigenesis. We previously discovered an internal ribosome entry site (IRES) that is located at the 5'-untranslated region (UTR) of p53 mRNA and found that the IRES activity increases following DNA damage. However, the mechanism underlying IRES-mediated p53 translation in response to DNA damage is still poorly understood. In this study, we discovered that translational control protein 80 (TCP80) has increased binding to the p53 mRNA in vivo following DNA damage. Overexpression of TCP80 also leads to increased p53 IRES activity in response to DNA damage. TCP80 has increased association with RNA helicase A (RHA) following DNA damage and overexpression of TCP80, along with RHA, leads to enhanced expression of p53. Moreover, we found that MCF-7 breast cancer cells with decreased expression of TCP80 and RHA exhibit defective p53 induction following DNA damage and diminished expression of its downstream target PUMA, a proapoptotic protein. Taken together, our discovery of the function of TCP80 and RHA in regulating p53 IRES and p53 induction following DNA damage provides a better understanding of the mechanisms that regulate IRES-mediated p53 translation in response to genotoxic stress.

Role of NADPH oxidase and xanthine oxidase in mediating inducible VT/VF and triggered activity in a canine model of myocardial ischemia.

BACKGROUND: Ventricular tachycardia or fibrillation (VT/VF) of focal origin due to triggered activity (TA) from delayed afterdepolarizations (DADs) is reproducibly inducible after anterior coronary artery occlusion. Both VT/VF and TA can be blocked by reducing reactive oxygen species (ROS). We tested the hypothesis that inhibition of NADPH oxidase and xanthine oxidase would block VT/VF. METHODS: 69 dogs received apocynin (APO), 4 mg/kg intraveneously (IV), oxypurinol (OXY), 4 mg/kg IV, or both APO and OXY (BOTH) agents, or saline 3 h after coronary occlusion. Endocardium from ischemic sites (3-D mapping) was sampled for Rac1 (GTP-binding protein in membrane NADPH oxidase) activation or standard microelectrode techniques. Results (mean±SE, * p<0.05): VT/VF originating from ischemic zones was blocked by APO in 6/10 *, OXY in 4/9 *, BOTH in 5/8 * or saline in 1/27; 11/16 VT/VFs blocked were focal. In isolated myocardium, TA was blocked by APO (10(-6) M) or OXY (10(-8) M). Rac1 levels in ischemic endocardium were decreased by APO or OXY. CONCLUSION: APO and OXY suppressed focal VT/VF due to DADs, but the combination of the drugs was not more effective than either alone. Both drugs inhibited ischemic Rac1 with inhibition by OXY suggesting ROS-induced ROS. The inability to totally prevent VT/VF suggests that other mechanisms also contribute to ischemic VT.

Phosphorylation of Nox1 regulates association with NoxA1 activation domain.

RATIONALE: Activation of Nox1 initiates redox-dependent signaling events crucial in the pathogenesis of vascular disease. Selective targeting of Nox1 is an attractive potential therapy, but requires a better understanding of the molecular modifications controlling its activation. OBJECTIVE: To determine whether posttranslational modifications of Nox1 regulate its activity in vascular cells. METHODS AND RESULTS: We first found evidence that Nox1 is phosphorylated in multiple models of vascular disease. Next, studies using mass spectroscopy and a pharmacological inhibitor demonstrated that protein kinase C-beta1 mediates phosphorylation of Nox1 in response to tumor necrosis factor-α. siRNA-mediated silencing of protein kinase C-beta1 abolished tumor necrosis factor-α-mediated reactive oxygen species production and vascular smooth muscle cell migration. Site-directed mutagenesis and isothermal titration calorimetry indicated that protein kinase C-beta1 phosphorylates Nox1 at threonine 429. Moreover, Nox1 threonine 429 phosphorylation facilitated the association of Nox1 with the NoxA1 activation domain and was necessary for NADPH oxidase complex assembly, reactive oxygen species production, and vascular smooth muscle cell migration. CONCLUSIONS: We conclude that protein kinase C-beta1 phosphorylation of threonine 429 regulates activation of Nox1 NADPH oxidase.

Nox1 NADPH oxidase is necessary for late but not early myocardial ischaemic preconditioning.

AIMS: Ischaemic preconditioning (IPC) is an adaptive mechanism that renders the myocardium resistant to injury from subsequent hypoxia. Although reactive oxygen species (ROS) contribute to both the early and late phases of IPC, their enzymatic source and associated signalling events have not yet been understood completely. Our objective was to investigate the role of the Nox1 NADPH oxidase in cardioprotection provided by IPC. METHODS AND RESULTS: Wild-type (WT) and Nox1-deficient mice were treated with three cycles of brief coronary occlusion and reperfusion, followed by prolonged occlusion either immediately (early IPC) or after 24 h (late IPC). Nox1 deficiency had no impact on the cardioprotection afforded by early IPC. In contrast, deficiency of Nox1 during late IPC resulted in a larger infarct size, cardiac remodelling, and increased myocardial apoptosis compared with WT hearts. Furthermore, expression of Nox1 in WT hearts increased in response to late IPC. Deficiency of Nox1 abrogated late IPC-mediated activation of cardiac nuclear factor-κB (NF-κB) and induction of tumour necrosis factor-α (TNF-α) in the heart and circulation. Finally, knockdown of Nox1 in cultured cardiomyocytes prevented TNF-α induction of NF-κB and the protective effect of IPC on hypoxia-induced apoptosis. CONCLUSIONS: Our data identify a critical role for Nox1 in late IPC and define a previously unrecognized link between TNF-α and NF-κB in mediating tolerance to myocardial injury. These findings have clinical significance considering the emergence of Nox1 inhibitors for the treatment of cardiovascular disease.

Activation of cannabinoid CB1 receptors modulates evoked action potentials in rat retinal ganglion cells.

Activation of cannabinoid CB1 receptors (CB1Rs) regulates a variety of physiological functions in the vertebrate retina through modulating various types of ion channels. The aim of the present study was to investigate the effects of this receptor on cell excitability of rat retinal ganglion cells (RGCs) in retinal slices using whole-cell patch-clamp techniques. The results showed that under current-clamped condition perfusing WIN55212-2 (WIN, 5 µmol/L), a CB1R agonist, did not significantly change the spontaneous firing frequency and resting membrane potential of RGCs. In the presence of cocktail synaptic blockers, including excitatory postsynaptic receptor blockers CNQX and D-APV, and inhibitory receptor blockers bicuculline and strychnine, perfusion of WIN (5 µmol/L) hardly changed the frequencies of evoked action potentials by a series of positive current injection (from +10 to +100 pA). Phase-plane plot analysis showed that both average threshold voltage for triggering action potential and delay time to reach threshold voltage were not affected by WIN. However, WIN significantly decreased +dV/dtmax and -dV/dtmax of action potentials, suggestive of reduced rising and descending velocities of action potentials. The effects of WIN were reversed by co-application of SR141716, a CB1R selective antagonist. Moreover, WIN did not influence resting membrane potential of RGCs with synaptic inputs being blocked. These results suggest that activation of CB1Rs may regulate intrinsic excitability of rat RGCs through modulating evoked action potentials.