Novel marine natural products as effective TRPV1 channel blockers.

Chronic pain management poses a formidable challenge to healthcare, exacerbated by current analgesic options' limitations and adverse effects. Transient receptor potential vanilloid 1 (TRPV1), a non-selective cation channel, has emerged as a promising target for novel analgesics. However, safety and tolerability concerns have constrained the development of TRPV1 modulators. In this study, we explored marine-derived natural products as a source of potential TRPV1 modulators using high-throughput dye-uptake assays. We identified chrexanthomycins, a family of hexacyclic xanthones, exhibited potent TRPV1 inhibitory effects, with compounds cC and cF demonstrating the most significant activity. High-resolution patch-clamp assays confirmed the direct action of these compounds on the TRPV1 channel. Furthermore, in vivo assays revealed that cC and cF effectively suppressed capsaicin-induced pain sensation in mice, comparable to the known TRPV1 inhibitor, capsazepine. Structural-activity relationship analysis highlighted the importance of specific functional groups in modulating TRPV1 activity. Our findings underscore the therapeutic potential of chrexanthomycins and pave the way for further investigations into marine-derived TRPV1 modulators for pain management.

Nucleophilic Addition of 4,5-Dihydrooxazole Derivatives to Base Generated o-Quinone Methides: A Four-Component Reaction.

A novel method for joining four components together in a single pot leading to an assortment of N-amino-benzylated phenols is described. The method involves the addition of different Grignard reagents to various o-OBoc salicylaldehydes in the presence of assorted 4,5-dihydrooxazoles, followed by aqueous workup. Seventeen examples are presented with varied (-R, -R' -R″, -R‴, -R⁗, and Cn) substituents.

Evaluation of the relationship between cardiac calcification and cardiovascular disease using the echocardiographic calcium score in patients undergoing peritoneal dialysis: a cross-sectional study.

Introduction: An echocardiographic calcium score (ECS) predicts cardiovascular disease (CVD) in the general population. Its utility in peritoneal dialysis (PD) patients is unknown. Methods: This cross-sectional study assessed 125 patients on PD. The ECS (range 0-8) was compared between subjects with CVD and those without. Results: Among the subjects, 54 had CVD and 71 did not. Subjects with CVD were older (69 years vs. 56 years, P < 0.001) and had a higher prevalence of diabetes mellitus (DM) (81.5% vs. 45.1%, P < 0.001). They had lower diastolic blood pressure (72 mmHg vs. 81 mmHg, P < 0.001), lower phosphate (1.6 mmol/L vs. 1.9 mmol/L, P = 0.002), albumin (30 g/L vs. 32 g/L, P = 0.001), parathyroid hormone (34.4 pmol/L vs. 55.8 pmol/L, P = 0.002), total cholesterol (4.5 vs. 4.9, P = 0.047), LDL cholesterol (2.4 mmol/L vs. 2.8 mmol/L, P = 0.019) and HDL cholesterol (0.8 mmol/L vs. 1.1 mmol/L, P = 0.002). The ECS was found to be higher in subjects with CVD than in those without (2 vs. 1, P = 0.001). On multivariate analysis, only DM and age were independently associated with CVD. Conclusion: The ECS was significantly higher in PD patients with CVD than in those without, reflecting a higher vascular calcification burden in the former. It is a potentially useful tool to quantify vascular calcification in PD patients.

Rhythmic auditory stimulation incorporated in training improved movements in individuals with psychotic-like experiences.

Movement abnormalities, including movement slowing and irregular muscle contraction, exist in individuals with psychotic-like experiences (PLEs) and serve as vulnerable factors of developing psychotic diseases in the psychosis continuum. To date scarce studies have developed early intervention programs tackling these initial impairments, which may be caused by basal ganglia alterations, in the early stage of the psychosis course. Rhythmic auditory stimulation (RAS) is a technique of neurological music therapy and has been proved effective in inducing faster movements in patients with psychotic diseases. This pilot study examined if RAS incorporated in functional movement training reduced severity of movement slowing and irregular muscle contraction in individuals with PLEs. Seventeen individuals with PLEs were randomly allocated to receiving RAS or receiving no RAS and underwent daily 40-min movement training (picking up beans) for three weeks. This study used motion analysis to measure movement performance at pretest and posttest. Eighteen age- and gender-matched individuals without PLEs were also recruited to provide data of intact movements. Results showed that RAS may reduce severity of movement slowing and irregular muscle contraction in individuals with PLEs. This pilot study is one of the pioneering studies validating effectiveness of early intervention programs tackling movement abnormalities, which are initial impairments in the psychosis continuum, in individuals with PLEs.

Enhanced long-term potentiation and impaired learning in mice lacking alternative exon 33 of CaV1.2 calcium channel.

The CACNA1C (calcium voltage-gated channel subunit alpha 1 C) gene that encodes the CaV1.2 channel is a prominent risk gene for neuropsychiatric and neurodegenerative disorders with cognitive and social impairments like schizophrenia, bipolar disorders, depression and autistic spectrum disorders (ASD). We have shown previously that mice with exon 33 deleted from CaV1.2 channel (CaV1.2-exon 33-/-) displayed increased CaV1.2 current density and single channel open probability in cardiomyocytes, and were prone to develop arrhythmia. As Ca2+ entry through CaV1.2 channels activates gene transcription in response to synaptic activity, we were intrigued to explore the possible role of Cav1.2Δ33 channels in synaptic plasticity and behaviour. Homozygous deletion of alternative exon 33 resulted in enhanced long-term potentiation (LTP), and lack of long- term depression (LTD), which did not correlate with enhanced learning. Exon 33 deletion also led to a decrease in social dominance, sociability and social novelty. Our findings shed light on the effect of gain-of-function of CaV1.2Δ33 signalling on synaptic plasticity and behaviour and provides evidence for a link between CaV1.2 and distinct cognitive and social behaviours associated with phenotypic features of psychiatric disorders like schizophrenia, bipolar disorder and ASD.

An audit comparing management of patients with HFrEF at a DGH before and during the COVID-19 pandemic.

This audit compared the management of patients with heart failure with reduced ejection fraction (HFrEF) admitted to a district general hospital (DGH) during comparative eight month periods before and during the COVID-19 pandemic. The periods studied were from 1st February 2019 to 30th September 2019 and between the same dates in 2020. We investigated differences in mortality and patient characteristics (age, gender and new or prior diagnosis). For patients who survived to discharge and who were not referred to palliative care, we also investigated whether there were differences in rates of echocardiography and prescription of angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists and beta blockers. We found that the number of cases was lower during the pandemic and there was a lower mortality rate that was not statistically significant. There was a higher proportion of new cases (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.24 to 3.94, p=0.008) and of female patients (OR 2.03, 95%CI 1.14 to 3.61, p=0.019). For survivors, there was a non-significant decrease in prescription rates for ACE inhibitors and angiotensin II receptor antagonists (81.6% vs. 71.4%, p=0.137) that was not seen for beta blockers. The length of stay was increased and there was also an increase in the interval between admission and echocardiography in patients who were newly diagnosed. Regardless of time period, the time before echocardiography was significantly associated with length of stay.

An echocardiography-derived calcium score as a predictor of major adverse cardiovascular events in peritoneal dialysis patients-A prospective cohort study.

BACKGROUND: An echocardiography-derived calcium score (ECS) has been shown to predict cardiovascular (CV) mortality in the general population but has not been utilized in the dialysis population. METHODS: We conducted a prospective cohort study including 125 prevalent PD patients. Two blinded and independent echocardiographers determined the ECS for each subject at baseline. The primary outcome was the three-point major adverse cardiovascular events (MACE) which is a composite outcome comprising CV death, non-fatal myocardial infarction and non-fatal stroke. The secondary outcome was all-cause mortality. RESULTS: The mean age was 61 ± 13 years. The median follow-up duration was 40 months (range 1-50). Seventy six (60.8%) of the subjects had diabetes mellitus (DM). The median duration of dialysis was 32 (IQR 16-54) months. The incidences of MACE and all-cause mortality were 13.0 per 100 patient-years and 18.3 per 100 patient-years. Multivariate Cox regression analysis identified the following three independent predictors of MACE: ECS (HR 1.253/unit increase in ECS, 95% CI 1.014-1.547, p = .036), DM (HR 2.467, 95% CI 1.014-6.005, p = .047) and pre-existing cardiovascular disease (CVD) (HR 2.441, 95% CI 1.261-4.728, p = .008); and the following two predictors of all-cause mortality: pre-existing CVD (HR 2.156, 95% CI 1.251-3.714, p = .006) and serum albumin (HR 0.887/g/L increase in serum albumin, 95% CI 0.839-0.937, p < .001). CONCLUSION: The ECS appears to be a significant predictor of MACE in PD patients independently of DM and pre-existing CVD.

Positive life stories of Stroke-Survivor's spousal caregiving in Hong Kong: Lessons for policy and practice.

BACKGROUND: Advances in medical-care for immediately post-stroke mean that many stroke-survivors now live a normal lifespan, although they may suffer residual disability. They are often cared for at home by their spouse, who may be ill-prepared for this task, and may also have health concerns. As demands on formal services increase with population aging in Hong Kong, equipping spousal-caregivers with positive effective caring strategies is increasingly important. OBJECTIVE: To understand what constitutes positive spousal-caregiving for stroke-survivors in Hong Kong within the cultural lens of 'Zhong (Loyalty)' METHOD: Naturalistic qualitative research was employed to hear stories about positive caregiving from Hong Kong couples living with stroke sequelae. Three in-depth face-to-face semi-structured interviews were undertaken with eleven dyads (stroke-survivor alone, spousal-caregiver alone, then the couple together). Data validation was by member-checking, further questions, and feedback at a second interview, and corroboration by field-notes. FINDINGS: A strength-based interactive model of positive spousal-caregiving was described, whose core tenet was Zhong (Loyalty). This fostered, and in turn was nurtured by, three paired key behaviours (1. Learning new skills linked with satisfaction when efforts paid off; 2. Utilizing formal and informal resources linked with supporting others; 3. Cherishing and bringing out the best linked with managing life- and self-care). Couples' capacity to develop these behaviours reflected their inner strengths. CONCLUSIONS: Couples who practiced positive caring and were resilient in the face of adversity were likely to optimise dyadic health and deal constructively with unexpected challenges. To address a looming shortfall between client need, and formal health and social services in Hong Kong, evidence-based policies are required to support effective, positive community-based spousal-caregiving.

Effects of different ischemic preconditioning strategies on physiological and cellular mechanisms of intestinal ischemia/reperfusion injury: Implication from an isolated perfused rat small intestine model.

BACKGROUND: Intestinal ischemia/reperfusion (I/R)-injury often results in sepsis and organ failure and is of major importance in the clinic. A potential strategy to reduce I/R-injury is the application of ischemic preconditioning (IPC) during which repeated, brief episodes of I/R are applied. The aim of this study was to evaluate physiological and cellular effects of intestinal I/R-injury and to compare the influence of in-vivo IPC (iIPC) with ex-vivo IPC (eIPC), in which blood derived factors and nerval regulations are excluded. METHODS: Using an established perfused rat intestine model, effects of iIPC and eIPC on physiological as well as cellular mechanisms of I/R-injury (60 min hypoxia, 30 min reperfusion) were investigated. iIPC was applied by three reversible occlusions of the mesenteric artery in-vivo for 5 min followed by 5 min of reperfusion before isolating the small intestine, eIPC was induced by stopping the vascular perfusion ex-vivo 3 times for 5 min followed by 5 min of reperfusion after isolation of the intestine. Study groups (each N = 8-9 animals) were: iIPC, eIPC, I/R (iIPC group), I/R (eIPC group), iIPC+I/R, eIPC+I/R, no intervention/control (iIPC group), no intervention/control (eIPC group). Tissue morphology/damage, metabolic functions, fluid shifts and barrier permeability were evaluated. Cellular mechanisms were investigated using signaling arrays. RESULTS: I/R-injury decreased intestinal galactose uptake (iIPC group: p<0.001), increased vascular perfusion pressure (iIPC group: p<0.001; eIPC group: p<0.01) and attenuated venous flow (iIPC group: p<0.05) while lactate-to-pyruvate ratio (iIPC group, eIPC group: p<0.001), luminal flow (iIPC group: p<0.001; eIPC group: p<0.05), goblet cell ratio (iIPC group, eIPC group: p<0.001) and apoptosis (iIPC group, eIPC group: p<0.05) were all increased. Application of iIPC prior to I/R increased vascular galactose uptake (P<0.05) while eIPC had no significant impact on parameters of I/R-injury. On cellular level, I/R-injury resulted in a reduction of the phosphorylation of several MAPK signaling molecules. Application of iIPC prior to I/R increased phosphorylation of JNK2 and p38δ while eIPC enhanced CREB and GSK-3α/ß phosphorylation. CONCLUSION: Intestinal I/R-injury is associated with major physiological and cellular changes. However, the overall influence of the two different IPC strategies on the acute phase of intestinal I/R-injury is rather limited.

Opposing roles of E3 ligases TRIM23 and TRIM21 in regulation of ion channel ANO1 protein levels.

Anoctamin-1 (ANO1) (TMEM16A) is a calcium-activated chloride channel that plays critical roles in diverse physiological processes, such as sensory transduction and epithelial secretion. ANO1 levels have been shown to be altered under physiological and pathological conditions, although the molecular mechanisms that control ANO1 protein levels remain unclear. The ubiquitin-proteasome system is known to regulate the levels of numerous ion channels, but little information is available regarding whether and how ubiquitination regulates levels of ANO1. Here, we showed that two E3 ligases, TRIM23 and TRIM21, physically interact with the C terminus of ANO1. In vitro and in vivo assays demonstrated that whereas TRIM23 ubiquitinated ANO1 leading to its stabilization, TRIM21 ubiquitinated ANO1 and induced its degradation. Notably, ANO1 regulation by TRIM23 and TRIM21 is involved in chemical-induced pain sensation, salivary secretion, and heart-rate control in mice, and TRIM23 also mediates ANO1 upregulation induced by epidermal growth factor treatment. Our results suggest that these two antagonistic E3 ligases act together to control ANO1 expression and function. Our findings reveal a previously unrecognized mechanism for regulating ANO1 protein levels and identify a potential molecular link between ANO1 regulation, epidermal growth factor, and other signaling pathways.

Healthcare Professional Experiences of Clinical Incident in Hong Kong: A Qualitative Study.

BACKGROUND: Studies showed that adverse events within health care settings can lead to two victims. The first victim is the patient and family and the second victim is the involved healthcare professionals. However, there is a lack of research studying the experiences of healthcare professionals encountering clinical incidents in Hong Kong. This paper reports a qualitative study in exploring the healthcare professional experiences of clinical incident, their impacts and needs. METHODS: This study is the second part of the mixed research method with two studies conducted in a cluster of hospitals in Hong Kong. Study 1 was a quantitative questionnaire survey and Study 2 was a qualitative In-Depth Interview. In study 2, a semi-interview guide was used. RESULTS: Results showed that symptoms experienced after the clinical incident were mostly from psychological, physical, then social and lastly spiritual aspects which were consistent with those found in study 1 and other studies. Using content analysis for analyzing the impacts, four themes were identified. Concerning the impacts immediately from the clinical incident, two themes emerged were 1) facing emotion distress and 2) maintaining rationality. Regarding the impacts after the clinical incident, another two themes were 3) managing further emotional distress 4) restoring personal wellness. With regard to the needs after clinical incidents, three themes emerged were 1) self-recovery; 2) senior good mentoring and 3) positive organization climate with emphasis on enhancement of training and development of a positive practice culture. CONCLUSION: Great impacts are found with healthcare professionals encountering clinical incidents from a holistic perspective. They need time for self-recovery with support from good supervisors, peers and a caring environment. Some recommendations based on the findings of the study are made.

Treatment of Severe Tumoral Calcinosis with Teriparatide in a Dialysis Patient after Total Parathyroidectomy.

Tumoral calcinosis is a rare but debilitating condition that can affect dialysis patients. Optimal management is largely unknown. We report the clinical course, treatment, and outcome of a peritoneal dialysis (PD) patient who developed tumoral calcinosis refractory to conventional treatment but improved with teriparatide therapy. A 26-year-old lady on PD for 2 years presented to us with tumoral calcinosis involving bilateral hands. Response to surgical excision, parathyroidectomy, and conversion to hemodialysis failed to result in sustained remission, and tumoral calcinosis progressed. After total parathyroidectomy, the patient had transient but partial remission in which her calcinosis deposits remained but were asymptomatic without pain or clinical signs of inflammation. However, she later experienced a relapse with involvement of the left elbow, right shoulder, right hip, and right thigh. Tumoral calcinosis remained uncontrolled resulting in debilitation, likely attributable to poor calcium and phosphate control because of adynamic bone disease after parathyroidectomy despite treatment of superimposed tuberculosis and therapy with sodium thiosulphate and pamidronic acid. Clinical improvement was however evident after the use of teriparatide. Asymptomatic hypocalcemia occurred after teriparatide therapy but resolved after 2 months. In conclusion, teriparatide appears to be useful for treating tumoral calcinosis in the presence of adynamic bone disease. Hypocalcemia can occur in the initial months of therapy.

Enhanced remediation of BDE-209 in contaminated mangrove sediment by planting and aquaculture effluent.

Toxic and persistent flame retardant (BDE-209) and aquaculture effluent (AE) are ubiquitous in coastal environments, but how their co-existence influences their fate is not yet investigated. This study investigated AE effects on remediation and uptake of BDE-209 by Kandelia obovata (Ko) and Avicennia marina (Am), true and dominant mangrove species. After 12-months, a significant removal of BDE-209 was achieved in planted mangrove sediment and the removal was significantly enhanced by AE addition, possibly due to the enhancement of nitrogen (N) and phosphorous (P) content in sediment. Residual percentages of parent BDE-209 in Ko and Am planted sediments without AE were 61.4% and 70.9%, respectively, but decreased to 46.9% and 48.0% with AE addition after 12-months. A similar trend was found in unplanted sediment, with 86.5% and 65.3% of BDE-209 retained in sediments without and with AE addition, respectively. The results demonstrated that AE addition not only increased the debromination of BDE-209 in all treated sediments with the production of debrominated congeners (de-PBDEs) like di- to nona-BDEs in unplanted and planted sediments, but also enhanced the take up of BDE-209 in Ko root, and de-PBDEs in both Ko and Am, thus enhancing the phytoremediation of BDE-209 in contaminated sediments.

Physiological response and oxidative transformation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) by a Chlorella isolate.

Polybrominated diphenyl ethers (PBDEs) are ubiquitous, toxic and persistent pollutants in environments. Microalgae frequent exposed to these pollutants may possess defense mechanisms against their toxicity and have the ability to metabolize them, thus are important in bioremediation. This study investigated the mechanism of a Chlorella isolate to degrade BDE-47, a common PBDE congener, and its subcellular responses to BDE-47 stress. Results showed that 86-98% of the spiked BDE-47 was removed by Chlorella via adsorption, uptake and metabolism. BDE-47 was metabolized through debromination, hydroxylation and methoxylation. The oxidative transformation to hydroxylated products was the initial and main metabolic process. BDE-47 induced the production of hydrogen peroxide (H2O2) in cell wall, plasma membrane and chloroplast of Chlorella, and such increase was regulated by nicotinamide adenine dinucleotide phosphate oxidase and H2O2-producing peroxidases (PODs). The activity of H2O2-consuming PODs and the content of glutathione were also significantly enhanced to detoxify the oxidative stress.

Changes of substrate microbial biomass and community composition in a constructed mangrove wetland for municipal wastewater treatment during 10-years operation.

Constructed wetlands (CWs) have been used for wastewater treatment for decades, but research on microorganisms involved, especially long-term changes, is still limited. In this study, we evaluated changes in the substrate microbial community in a pilot-scale horizontal subsurface-flow constructed mangrove wetland during 10-years operation. In the 3rd year of operation, microbial biomass carbon and phospholipid fatty acids (PLFAs) reached peak values in two vegetated belts planted with Aegiceras corniculatum (Ac) and Kandelia obovata (Ko), respectively, then stabilized or declined in the 9th and 10th years of operation. PLFA profiles reflecting microbial community compositions varied significantly in the Ac belt during the operation period. Principal component (PCA) and redundancy analyses (RDA) revealed that microbial community compositions were significantly correlated with organic matter content, especially in the 9th and 10th years of operation, implying that the substrate microbial community in constructed mangrove wetland is sensitive to substrate characteristics and can be used as an indicator for long-term performance of CWs.

Nucleophilic Imines and Electrophilic o-Quinone Methides, a Three-Component Assembly of Assorted 3,4-Dihydro-2H-1,3-benzoxazines.

A one-pot method for joining three separate components leading to an assortment of N-substituted 3,4-dihydro-2H-1,3-benzoxazines is described. The method involves the addition of a Grignard reagent to an o-OBoc salicylaldehyde in the presence of an imine. With a variety of components, 15 examples are presented, including the diastereoselective incorporation of chiral imines.

Remote ischemic preconditioning attenuates intestinal mucosal damage: insight from a rat model of ischemia-reperfusion injury.

BACKGROUND: Remote ischemic preconditioning (RIPC) is a phenomenon, whereby repeated, non-lethal episodes of ischemia to an organ or limb exert protection against ischemia-reperfusion (I/R) injury in distant organs. Despite intensive research, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms, especially in the intestine. Aim of this study was to evaluate possible protective effects RIPC on intestinal I/R injury. METHODS: Thirty rats were randomly assigned to four groups: I/R; I/R + RIPC; Sham; Sham + RIPC. Animals were anesthetized and the superior mesenteric artery was clamped for 30 min, followed by 60 min of reperfusion. RIPC-treated rats received 3 × 5 min of bilateral hindlimb I/R prior to surgery, sham groups obtained laparotomy without clamping. After I/R injury serum/tissue was analyzed for: Mucosal damage, Caspase-3/7 activity, expression of cell stress proteins, hydrogen peroxide (H2O2) and malondialdehyde (MDA) production, Hypoxia-inducible factor-1α (HIF-1α) protein expression and matrix metalloproteinase (MMP) activity. RESULTS: Intestinal I/R resulted in increased mucosal injury (P < 0.001) and elevated Caspase-3/7 activity (P < 0.001). RIPC significantly reduced the histological signs of intestinal I/R injury (P < 0.01), but did not affect Caspase-3/7 activity. Proteome profiling suggested a RIPC-mediated regulation of several cell stress proteins after I/R injury: Cytochrome C (+ 157%); Cited-2 (- 39%), ADAMTS1 (+ 74%). Serum concentrations of H2O2 and MDA remained unchanged after RIPC, while the reduced intestinal injury was associated with increased HIF-1α levels. Measurements of MMP activities in serum and intestinal tissue revealed an attenuated gelatinase activity at 130 kDa within the serum samples (P < 0.001) after RIPC, while the activity of MMPs within the intestinal tissue was not affected by I/R injury or RIPC. CONCLUSIONS: RIPC ameliorates intestinal I/R injury in rats. The underlying mechanisms may involve HIF-1α protein expression and a decreased serum activity of a 130 kDa factor with gelatinase activity.

Effects of hydroxyethyl starch (HES 130/0.42) on endothelial and epithelial permeability in vitro.

Hydroxyethyl starch (HES) is employed to sustain normovolemia in patients. Using a perfused organ model, we recently showed that HES impairs the intestinal barrier which is constituted of endothelial and epithelial cell layers. However, the target cells and molecular actions of HES in the intestine are mainly unknown. Employing a model of human endothelial (HUVEC) and intestinal epithelial cells (Caco-2), we investigated the impact of HES, albumin and HES/albumin on cellular integrity/permeability and evaluated underlying molecular mechanisms. Monolayers of HUVEC and Caco-2 were cultured with HES (3%), albumin (3%) or HES/albumin (1.5%/1.5%). Integrity and permeability of the cell layers were evaluated by FITC-dextran transfer, measurements of cell detachment, vitality, cell volume, LDH release and caspase-3/7 activity. Cellular mechanisms were analyzed by Westernblotting for P-akt, P-erk, claudin-3 and I-FABP. HES application resulted in higher numbers of non-adherent/floating HUVEC cells (P<0.05) but did not change vitality or cell volume. Both, HES and HES/albumin increased the permeability of HUVEC monolayers (P<0.001), while LDH release, caspase-3/7 activity, akt/erk phosphorylation and claudin-3 expression were not affected. HES and HES/albumin did not change any of the parameters in cultures of Caco-2 cells. HES is able to disturb the integrity of the endothelial but not the epithelial barrier in vitro. HES effects are unrelated to cell damage and apoptosis but may involve reduced cell-cell or cell-matrix adhesion.

Tissue-selective restriction of RNA editing of CaV1.3 by splicing factor SRSF9.

Adenosine DeAminases acting on RNA (ADAR) catalyzes adenosine-to-inosine (A-to-I) conversion within RNA duplex structures. While A-to-I editing is often dynamically regulated in a spatial-temporal manner, the mechanisms underlying its tissue-selective restriction remain elusive. We have previously reported that transcripts of voltage-gated calcium channel CaV1.3 are subject to brain-selective A-to-I RNA editing by ADAR2. Here, we show that editing of CaV1.3 mRNA is dependent on a 40 bp RNA duplex formed between exon 41 and an evolutionarily conserved editing site complementary sequence (ECS) located within the preceding intron. Heterologous expression of a mouse minigene that contained the ECS, intermediate intronic sequence and exon 41 with ADAR2 yielded robust editing. Interestingly, editing of CaV1.3 was potently inhibited by serine/arginine-rich splicing factor 9 (SRSF9). Mechanistically, the inhibitory effect of SRSF9 required direct RNA interaction. Selective down-regulation of SRSF9 in neurons provides a basis for the neuron-specific editing of CaV1.3 transcripts.