Vaccarin alleviates septic cardiomyopathy by potentiating NLRP3 palmitoylation and inactivation.

BACKGROUND: Sepsis often leads to significant morbidity and mortality due to severe myocardial injury. As is known, the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome crucially contributes to septic cardiomyopathy (SCM) by facilitating the secretion of interleukin (IL)-1ß and IL-18. The removal of palmitoyl groups from NLRP3 is a crucial step in the activation of the NLRP3 inflammasome. Thus, the potential inhibitors that regulate the palmitoylation and inactivation of NLRP3 may significantly diminish sepsis-induced cardiac dysfunction. PURPOSE: The present study sought to explore the effects of the prospective flavonoid compounds targeting NLRP3 on SCM and to elucidate the associated underlying mechanisms. STUDY DESIGN: The palmitoylation and activation of NLRP3 were detected in H9c2 cells and C57BL/6 J mice. METHODS/RESULTS: Echocardiography, histological staining, western blotting, co-immunoprecipitation, qPCR, ELISA and network pharmacology were used to assess the impact of vaccarin (VAC) on SCM in mice subjected to lipopolysaccharide (LPS) injection. From the collection of 74 compounds, we identified that VAC had the strongest capability to suppress NLRP3 luciferase report gene activity in cardiomyocytes, and the anti-inflammatory characteristics of VAC were further ascertained by the network pharmacology. Exposure of LPS triggered apoptosis, inflammation, oxidative stress, mitochondrial disorder in cardiomyocytes. The detrimental alterations were significantly reversed upon VAC treatment in both septic mice and H9c2 cells exposed to LPS. In vivo experiments demonstrated that VAC treatment alleviated septic myocardial injury, indicated by enhanced cardiac function parameters, preserved cardiac structure, and reduced inflammation/oxidative response. Mechanistically, VAC induced NLRP3 palmitoylation to inactivate NLRP3 inflammasome by acting on zDHHC12. In support, the NLRP3 agonist ATP and the acylation inhibitor 2-bromopalmitate (2-BP) prevented the effects of VAC. CONCLUSION: Our findings suggest that VAC holds promise in protecting against SCM by mitigating cardiac oxidative stress and inflammation via priming NLRP3 palmitoylation and inactivation. These results lay the solid basis for further assessment of the therapeutic potential of VAC against SCM.

Pharmacology of hydrogen sulfide and its donors in cardiometabolic diseases.

Cardiometabolic diseases (CMDs) are major contributors to global mortality, emphasizing the critical need for novel therapeutic interventions. Hydrogen sulfide (H2S) has garnered enormous attention as a significant gasotransmitter with various physiological, pathophysiological, and pharmacological impacts within mammalian cardiometabolic systems. In addition to its roles in attenuating oxidative stress and inflammatory response, burgeoning research emphasizes the significance of H2S in regulating proteins via persulfidation, a well-known modification intricately associated with the pathogenesis of CMDs This review seeks to investigate recent updates on the physiological actions of endogenous H2S and the pharmacological roles of various H2S donors in addressing diverse aspects of CMDs across cellular, animal, and clinical studies. Of note, advanced methodologies including multi-omics, intestinal microflora analysis, organoid and single-cell sequencing techniques are gaining traction due to their ability to offer comprehensive insights into biomedical research. These emerging approaches hold promise in characterizing the pharmacological roles of H2S in health and diseases. We will critically assesse the current literatures to clarify the roles of H2S in diseases while also delineating the opportunities and challenges they present in H2S-based pharmacotherapy for CMDs. Significance Statement The comprehensive review covers recent developments in H2S biology and pharmacology in CMDs. Endogenous H2S and its donors show great promise for the management of CMDs by regulating numerous proteins and signaling pathways. The emergence of new technologies will considerably advance the pharmacological research and clinical translation of H2S.

Cichoric acid ameliorates sepsis-induced acute kidney injury by inhibiting M1 macrophage polarization.

Cichoric acid (CA), a widely utilized polyphenolic compound in medicine, has garnered significant attention due to its potential health benefits. Sepsis-induced acute kidney disease (AKI) is related with an elevated risk of end-stage kidney disease (ESKD). However, it remains unclear whether CA provides protection against septic AKI. The aim of this study is to investigated the protective effect and possible mechanisms of CA against LPS-induced septic AKI. Sepsis-induced AKI was induced in mice through intraperitoneal injection of lipopolysaccharide (LPS), and RAW264.7 macrophages were incubated with LPS. LPS exposure significantly increased the levels of M1 macrophage biomarkers while reducing the levels of M2 macrophage indicators. This was accompanied by the release of inflammatory factors, superoxide anion production, mitochondrial dysfunction, activation of succinate dehydrogenase (SDH), and subsequent succinate formation. Conversely, pretreatment with CA mitigated these abnormalities. CA attenuated hypoxia-inducible factor-1α (HIF-1α)-induced glycolysis by lifting the NAD+/NADH ratio in macrophages. Additionally, CA disrupted the K (lysine) acetyltransferase 2A (KAT2A)/α-tubulin complex, thereby reducing α-tubulin acetylation and subsequently inactivating the NLRP3 inflammasome. Importantly, administration of CA ameliorated LPS-induced renal pathological damage, apoptosis, inflammation, oxidative stress, and disturbances in mitochondrial function in mice. Overall, CA restrained HIF-1α-mediated glycolysis via inactivation of SDH, leading to NLRP3 inflammasome inactivation and the amelioration of sepsis-induced AKI.

Potential clinical value of fibrinogen-like protein 1 as a serum biomarker for the identification of diabetic cardiomyopathy.

Diabetic individuals with diabetic cardiomyopathy (DbCM) present with abnormal myocardial structure and function. DbCM cannot be accurately diagnosed due to the lack of suitable diagnostic biomarkers. In this study, 171 eligible participants were divided into a healthy control (HC), type 2 diabetes mellitus (T2DM) patients without DbCM (T2DM), or DbCM group. Serum fibrinogen-like protein 1 (FGL-1) and other biochemical parameters were determined for all participants. Serum FGL-1 levels were significantly higher in patients with DbCM compared with those in the T2DM group and HCs. Serum FGL-1 levels were negatively correlated with left ventricular fractional shortening and left ventricular ejection fraction (LVEF) and positively correlated with left ventricular mass index in patients with DbCM after adjusting for age, sex and body mass index. Interaction of serum FGL-1 and triglyceride levels on LVEF was noted in patients with DbCM. A composite marker including serum FGL-1 and triglycerides could differentiate patients with DbCM from those with T2DM and HCs with an area under the curve of 0.773 and 0.789, respectively. Composite marker levels were negatively correlated with N-terminal B-type natriuretic peptide levels in patients with DbCM. Circulating FGL-1 may therefore be a valuable index reflecting cardiac functions in DbCM and to diagnose DbCM.

Biomimetic Nanoporous Transparent Universal Fire-Resistant Coatings.

The inherent flammability of most polymeric materials poses a significant fire hazard, leading to substantial property damage and loss of life. A universal flame-retardant protective coating is considered as a promising strategy to mitigate such risks; however, simultaneously achieving high transparency of the coatings remains a great challenge. Here, inspired by the moth eye effect, we designed a nanoporous structure into a protective coating that leverages a hydrophilic-hydrophobic interactive assembly facilitated by phosphoric acid protonated amino siloxane. The coating demonstrates robust adhesion to a diverse range of substrates, including but not limited to fabrics, foams, paper, and wood. As expected, its moth-eye-inspired nanoporous structure conferred a high visible light transparency of >97% and water vapor transmittance of 96%. The synergistic effect among phosphorus (P), nitrogen (N), and silicon (Si) largely enhanced the char-forming ability and restricted the decomposition of the coated substrates, which successfully endowed the coating with high fire-fighting performance. More importantly, for both flexible and rigid substrates, the coated samples all possessed great mechanical properties. This work provides a new insight for the design of protective coatings, particularly focusing on achieving high transparency.

Chicoric acid ameliorates sepsis-induced cardiomyopathy via regulating macrophage metabolism reprogramming.

BACKGROUND: Sepsis-related cardiac dysfunction is believed to be a primary cause of high morbidity and mortality. Metabolic reprogramming is closely linked to NLRP3 inflammasome activation and dysregulated glycolysis in activated macrophages, leading to inflammatory responses in septic cardiomyopathy. Succinate dehydrogenase (SDH) and succinate play critical roles in the progression of metabolic reprogramming in macrophages. Inhibition of SDH may be postulated as an effective strategy to attenuate macrophage activation and sepsis-induced cardiac injury. PURPOSE: This investigation was designed to examine the role of potential compounds that target SDH in septic cardiomyopathy and the underlying mechanisms involved. METHODS/RESULTS: From a small molecule pool containing about 179 phenolic compounds, we found that chicoric acid (CA) had the strongest ability to inhibit SDH activity in macrophages. Lipopolysaccharide (LPS) exposure stimulated SDH activity, succinate accumulation and superoxide anion production, promoted mitochondrial dysfunction, and induced the expression of hypoxia-inducible factor-1α (HIF-1α) in macrophages, while CA ameliorated these changes. CA pretreatment reduced glycolysis by elevating the NAD+/NADH ratio in activated macrophages. In addition, CA promoted the dissociation of K(lysine) acetyltransferase 2A (KAT2A) from α-tubulin, and thus reducing α-tubulin acetylation, a critical event in the assembly and activation of NLRP3 inflammasome. Overexpression of KAT2A neutralized the effects of CA, indicating that CA inactivated NLRP3 inflammasome in a specific manner that depended on KAT2A inhibition. Importantly, CA protected the heart against endotoxin insult and improved sepsis-induced cardiac mitochondrial structure and function disruption. Collectively, CA downregulated HIF-1α expression via SDH inactivation and glycolysis downregulation in macrophages, leading to NLRP3 inflammasome inactivation and the improvement of sepsis-induced myocardial injury. CONCLUSION: These results highlight the therapeutic role of CA in the resolution of sepsis-induced cardiac inflammation.

The relationship between mean daily step counts and pulmonary complications after thoracoscopic lobectomy in elderly patients: A propensity score matching study / 中国胸心血管外科临床杂志

@#Objective     To investigate the relationship between preoperative mean daily step counts and pulmonary complications after thoracoscopic lobectomy in elderly patients. Methods     From 2018 to 2021, the elderly patients with pulmonary complications after thoracoscopic lobectomy were included. A 1∶1 propensity score matching was performed with patients without pulmonary complications. The clinical data were compared between the two groups. Results    Totally, 100 elderly patients with pulmonary complications were enrolled, including 78 males and 22 females, aged 66.4±4.5 years. And 100 patients without pulmonary complications were matched, including 71 males and 29 females aged 66.2±5.0 years. There was no significant difference in the preoperative data between the two groups (P>0.05). Compared to the patients with pulmonary complications, the ICU stay was shorter (8.1±4.4 h vs. 12.9±7.5 h, P<0.001), the first out-of-bed activity time was earlier (8.8±4.5 h vs. 11.2±6.1 h, P=0.002), and the tube incubation time was shorter (19.3±9.2 h vs. 22.5±9.4 h, P=0.015) in the patients wihout pulmonary complications. There was no statistical difference in other perioperative data between the two groups (P>0.05). The mean daily step counts in the pulmonary complications group were significantly less than that in the non-pulmonary complications group (4 745.5±2 190.9 steps vs. 6 821.1± 2 542.0 steps, P<0.001). The daily step counts showed an upward trend for three consecutive days in the two groups, but the difference was not significant. Conclusion     The decline of preoperative mean daily step counts is related to pulmonary complications after thoracoscopic lobectomy in elderly patients. Recording daily step counts can promote preoperative active exercise training for hospitalized patients.

Ozonated autohemotherapy combined with pulsed radiofrequency in the treatment of thoracic postherpetic neuralgia in older adults: a retrospective study.

Postherpetic neuralgia (PHN) seriously affects the quality of life of the elderly population. This study aimed to evaluate the efficacy of ozonated autohemotherapy (O3-AHT) combined with pulsed radiofrequency (PRF) in the treatment of thoracic PHN in older adults. The medical records of patients with thoracic PHN aged 65 years and older from June 2018 until March 2021 in Shengli Oilfield Central Hospital were reviewed. They were assigned into two groups: PRF alone (PRF group, n = 107) and PRF combined with O3-AHT (PRF + O3-AHT group, n = 109). Visual Analogue Scale for pain was evaluated at pre-treatment, 1 day, 1, 3 and 6 months after treatment. Quality of life and sleep quality were assessed using Short-Form 36 Health Survey and Athens Insomnia Scale at pre-treatment and 6 months post-treatment, respectively. The median age of patients in the PRF and PRF + O3-AHT groups were 69 (67-73) years and 68 (67-72) years, respectively. The former included 62 females and the latter included 51 females. Compared with pre-treatment, the Visual Analogue Scale scores of two groups declined at post-treatment. Patients in the PRF + O3-AHT group showed obviously lower Visual Analogue Scale scores compared with those in the PRF group at 1, 3, and 6 months after treatment and they had earlier withdrawal time for drugs. However, dizziness, tachycardia, sleepiness, and nausea were presented after combination therapy. These symptoms resolved spontaneously after a period of rest. Additionally, O3-AHT combined with PRF was associated with a significant decrease in the Athens Insomnia Scale score and with a significant improvement in every dimension of the Short-Form 36 Health Survey. To conclude, O3-AHT combined with PRF is an effective way to relieve thoracic PHN in older patients.

TNF-α-Induced KAT2A Impedes BMMSC Quiescence by Mediating Succinylation of the Mitophagy-Related Protein VCP.

Regular quiescence and activation are important for the function of bone marrow mesenchymal stem cells (BMMSC), multipotent stem cells that are widely used in the clinic due to their capabilities in tissue repair and inflammatory disease treatment. TNF-α is previously reported to regulate BMMSC functions, including multilineage differentiation and immunoregulation. The present study demonstrates that TNF-α impedes quiescence and promotes the activation of BMMSC in vitro and in vivo. Mechanistically, the TNF-α-induced expression of KAT2A promotes the succinylation of VCP at K658, which inhibits the interaction between VCP and MFN1 and thus inhibits mitophagy. Furthermore, activated BMMSC exhibits stronger fracture repair and immunoregulation functions in vivo. This study contributes to a better understanding of the mechanisms of BMMSC quiescence and activation and to improving the effectiveness of BMMSC in clinical applications.

Targeting macrophage M1 polarization suppression through PCAF inhibition alleviates autoimmune arthritis via synergistic NF-κB and H3K9Ac blockade.

Sustained inflammatory invasion leads to joint damage and progressive disability in several autoimmune rheumatic diseases. In recent decades, targeting M1 macrophage polarization has been suggested as a promising therapeutic strategy for autoimmune arthritis. P300/CBP-associated factor (PCAF) is a histone acetyltransferase (HAT) that exhibits a strong positive relationship with the proinflammatory microenvironment. However, whether PCAF mediates M1 macrophage polarization remains poorly studied, and whether targeting PCAF can protect against autoimmune arthritis in vivo remains unclear. Commonly used drugs can cause serious side effects in patients because of their extensive and nonspecific distribution in the human body. One strategy for overcoming this challenge is to develop drug nanocarriers that target the drug to desirable regions and reduce the fraction of drug that reaches undesirable targets. In this study, we demonstrated that PCAF inhibition could effectively inhibit M1 polarization and alleviate arthritis in mice with collagen-induced arthritis (CIA) via synergistic NF-κB and H3K9Ac blockade. We further designed dextran sulfate (DS)-based nanoparticles (DSNPs) carrying garcinol (a PCAF inhibitor) to specifically target M1 macrophages in inflamed joints of the CIA mouse model via SR-A-SR-A ligand interactions. Compared to free garcinol, garcinol-loaded DSNPs selectively targeted M1 macrophages in inflamed joints and significantly improved therapeutic efficacy in vivo. In summary, our study indicates that targeted PCAF inhibition with nanoparticles might be a promising strategy for treating autoimmune arthritis via M1 macrophage polarization inhibition.

ALKBH5 facilitates CYP1B1 mRNA degradation via m6A demethylation to alleviate MSC senescence and osteoarthritis progression.

Improving health and delaying aging is the focus of medical research. Previous studies have shown that mesenchymal stem cell (MSC) senescence is closely related to organic aging and the development of aging-related diseases such as osteoarthritis (OA). m6A is a common RNA modification that plays an important role in regulating cell biological functions, and ALKBH5 is one of the key m6A demethylases. However, the role of m6A and ALKBH5 in MSC senescence is still unclear. Here, we found that the m6A level was enhanced and ALKBH5 expression was decreased in aging MSCs induced by multiple replications, H2O2 stimulation or UV irradiation. Downregulation of ALKBH5 expression facilitated MSC senescence by enhancing the stability of CYP1B1 mRNA and inducing mitochondrial dysfunction. In addition, IGF2BP1 was identified as the m6A reader restraining the degradation of m6A-modified CYP1B1 mRNA. Furthermore, Alkbh5 knockout in MSCs aggravated spontaneous OA in mice, and overexpression of Alkbh5 improved the efficacy of MSCs in OA. Overall, this study revealed a novel mechanism of m6A in MSC senescence and identified promising targets to protect against aging and OA.

USP7 promotes the osteoclast differentiation of CD14+ human peripheral blood monocytes in osteoporosis via HMGB1 deubiquitination.

Background: Abnormal osteoclast and osteoblast differentiation is an essential pathological process in osteoporosis. As an important deubiquitinase enzyme, ubiquitin-specific peptidase 7 (USP7) participates in various disease processes through posttranslational modification. However, the mechanism by which USP7 regulates osteoporosis remains unknown. Herein, we aimed to investigate whether USP7 regulates abnormal osteoclast differentiation in osteoporosis. Methods: The gene expression profiles of blood monocytes were preprocessed to analyze the differential expression of USP genes. CD14+ peripheral blood mononuclear cells (PBMCs) were isolated from whole blood collected from osteoporosis patients (OPs) and healthy donors (HDs), and the expression pattern of USP7 during the differentiation of CD14+ PBMCs into osteoclasts was detected by western blotting. The role of USP7 in the osteoclast differentiation of PBMCs treated with USP7 siRNA or exogenous rUSP7 was further investigated by the F-actin assay, TRAP staining and western blotting. Moreover, the interaction between high-mobility group protein 1 (HMGB1) and USP7 was investigated by coimmunoprecipitation, and the regulation of the USP7-HMGB1 axis in osteoclast differentiation was further verified. Osteoporosis in ovariectomized (OVX) mice was then studied using the USP7-specific inhibitor P5091 to identify the role of USP7 in osteoporosis. Results: The bioinformatic analyses and CD14+ PBMCs from osteoporosis patients confirmed that the upregulation of USP7 was associated with osteoporosis. USP7 positively regulates the osteoclast differentiation of CD14+ PBMCs in vitro. Mechanistically, USP7 promoted osteoclast formation by binding to and deubiquitination of HMGB1. In vivo, P5091 effectively attenuates bone loss in OVX mice. Conclusion: We demonstrate that USP7 promotes the differentiation of CD14+ PBMCs into osteoclasts via HMGB1 deubiquitination and that inhibition of USP7 effectively attenuates bone loss in osteoporosis in vivo.The translational potential of this article:The study reveals novel insights into the role of USP7 in the progression of osteoporosis and provides a new therapeutic target for the treatment of osteoporosis.

A novel Anti-ROS osteoblast-specific delivery system for ankylosing spondylitis treatment via suppression of both inflammation and pathological new bone formation.

Ankylosing spondylitis (AS) is a common rheumatic disorder distinguished by chronic inflammation and heterotopic ossification at local entheses sites. Currently available medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying anti-rheumatic drugs (DMARDs) and TNF inhibitors, are limited by side effects, high costs and unclear inhibitory effects on heterotopic ossification. Herein, we developed manganese ferrite nanoparticles modified by the aptamer CH6 (CH6-MF NPs) that can efficiently scavenge ROS and actively deliver siRNA into hMSCs and osteoblasts in vivo for effective AS treatment. CH6-MF NPs loaded with BMP2 siRNA (CH6-MF-Si NPs) effectively suppressed abnormal osteogenic differentiation under inflammatory conditions in vitro. During their circulation and passive accumulation in inflamed joints in the Zap70mut mouse model, CH6-MF-Si NPs attenuated local inflammation and rescued heterotopic ossification in the entheses. Thus, CH6-MF NPs may be an effective inflammation reliever and osteoblast-specific delivery system, and CH6-MF-Si NPs have potential for the dual treatment of chronic inflammation and heterotopic ossification in AS.

Prognostic and predictive significance of serum soluble scavenger receptor A in acute primary basal ganglia hemorrhage: A prospective cohort study.

BACKGROUND: Scavenger receptor A (SRA) can regulate immune response and is involved in pathophysiological processes of acute brain injury. We analyzed the prognostic role of serum soluble SRA in intracerebral hemorrhage (ICH). METHODS: In this prospective cohort study of 110 healthy controls and 110 patients with acute basal ganglia hemorrhage, serum soluble SRA concentrations were detected. Univariate analyses, followed by multivariate logistic regression analyses, were utilized to explore the relationship between serum soluble SRA concentrations and early neurologic deterioration (END) plus post-stroke 3-month poor prognosis (modified Rankin Scale scores of 3-6). RESULTS: Serum soluble SRA concentrations of patients were significantly higher than those of controls (median, 3.6 vs 0.9 ng/ml; P < 0.001). Serum soluble SRA concentrations of patients were independently correlated with hematoma volume (ß, 0.201; 95 % confidence interval (CI), 0.093-0.309; P = 0.001), National Institutes of Health Stroke Scale (NIHSS) scores (ß, 0.118; 95 % CI, 0.024-0.213; P = 0.024), and 3-month modified Rankin Scale scores (ß, 0.148; 95 % CI, 0.063-0.232; P = 0.001). Serum soluble SRA concentrations independently predicted END and poor 3-month prognosis with odds ratio values of 1.394 (95 % CI, 1.024-1.899; P = 0.035) and 1.441 (95 % CI, 1.016-2.044; P = 0.040) respectively. Serum soluble SRA concentrations were efficiently predictive of the development of END (ROC AUC 0.746; 95 % CI, 0.631-0.861) and poor 3-month prognosis (AUC, 0.773; 95 % CI, 0.685-0.861). Serum soluble SRA concentrations significantly improved AUCs of NIHSS score and hematoma volume to 0.889 (95 % CI, 0.829-0.948; P = 0.035) and 0.873 (95 % CI, 0.811-0.936; P = 0.036) for prognostic prediction. The END predictive ability of serum sSRA concentrations combined with NIHSS score and ICH volume (AUC, 0.900; 95 % CI, 0.835-0.965) was significantly superior to those of NIHSS score (P = 0.020) and hematoma volume (P = 0.022). The prognostic predictive capability of serum sSRA concentrations combined with NIHSS score and ICH volume (AUC, 0.907; 95 % CI, 0.852-0.962) substantially exceeded those of NIHSS score (P = 0.009) and hematoma volume (P = 0.005). CONCLUSIONS: Serum soluble SRA concentrations may reflect illness severity and neurologic function after ICH, indicating serum soluble SRA may serve as a promising prognostic biochemical marker of ICH.

Current status and development direction of immunomodulatory therapy for intervertebral disk degeneration.

Intervertebral disk (IVD) degeneration (IVDD) is a main factor in lower back pain, and immunomodulation plays a vital role in disease progression. The IVD is an immune privileged organ, and immunosuppressive molecules in tissues reduce immune cell (mainly monocytes/macrophages and mast cells) infiltration, and these cells can release proinflammatory cytokines and chemokines, disrupting the IVD microenvironment and leading to disease progression. Improving the inflammatory microenvironment in the IVD through immunomodulation during IVDD may be a promising therapeutic strategy. This article reviews the normal physiology of the IVD and its degenerative mechanisms, focusing on IVDD-related immunomodulation, including innate immune responses involving Toll-like receptors, NOD-like receptors and the complement system and adaptive immune responses that regulate cellular and humoral immunity, as well as IVDD-associated immunomodulatory therapies, which mainly include mesenchymal stem cell therapies, small molecule therapies, growth factor therapies, scaffolds, and gene therapy, to provide new strategies for the treatment of IVDD.

Variations in the toxicity and condition index of five bivalve species throughout a red tide event caused by Alexandrium catenella: A field study.

Harmful red tides in China have caused paralytic shellfish toxins (PSTs) pollution and led to severe socioeconomic effects in shellfish aquaculture. Although shellfish can survive harmful algal blooms, the effects on their Condition Index (CI) have been underestimated. This study sought to evaluate the effects of the profiles and levels of paralytic shellfish toxins on variations in the CI in bivalves under natural blooming conditions. We observed clear soft tissue lesions to varying degrees except in Mytilus galloprovincialis after toxin exposure. Among the five species of shellfish exposed in situ, only M. galloprovincialis accumulated PSTs content above the maximum permitted level (800 µg STX di-HCl eq./kg). The highest toxin content in all sample tissues was observed in Patinopecten yessoensis. Significant interspecies differences in PSTs accumulation among the five bivalve species were observed in the hepatopancreas. A total of nine PSTs components and four new C-11 hydroxyl metabolites (so-called M-toxins) toxins were detected, and detoxification diversity was observed among bivalves. We observed a higher proportion of M-toxin in early stages, and the proportions changed only slightly over time in M. galloprovincialis and Magallana gigas, thus accounting for the significantly higher metabolism rate. Notably, the CI in M. gigas and Argopecten irradians was positively correlated with lowest toxin accumulation of PSTs content, but significantly inhibited. In conclusion, our results revealed a significant inhibitory effect on the CI in shellfish, in a species specific manner, with distinct levels of inhibition correlated with different toxin metabolites. Our study revealed the toxin content of different bivalves exposed to a natural red tide environment and the consequent effects on growth, thus building a foundation for research on the mechanisms underlying the effects of PSTs on growth. These data establish the ecological and economic significance of the effects of harmful algal blooms on bivalves.

Formation mechanism and environmental drivers of Alexandrium catenella bloom events in the coastal waters of Qinhuangdao, China.

In the last 5 years, paralytic shellfish toxins (PSTs) have been recurrently detected in mollusks farmed in the mussel culture area of Qinhuangdao city, along with the occurrence of toxic outbreaks linked to dinoflagellate species of the Alexandrium genus. To understand the formation mechanism and variation of these events, continuous and comprehensive PSTs monitoring was carried out between 2017 and 2020. Through the analysis of both phytoplankton and cysts via light microscopy and quantitative polymerase chain reaction, it was shown that Alexandrium catenella was responsible for the production of PSTs, which consisted mainly of gonyautoxins 1,4 (GTX1/4, 87%) and GTX2/3 (13%). During bloom events in 2019, mussels accumulated the highest PSTs value (929 µg STX di-HCl eq·kg-1) in conjunction with the peak of cell abundances, and toxin profiles were consistent with high distributions of GTX1/4, GTX2/3, and Neosaxitoxin. Toxin metabolites vary in different substances and mainly transferred to a stable proportion of α-epimer: ß-epimers 3:1. The environmental drivers of Alexandrium blooms included the continuous rise of water temperature (>4 °C) and calm weather with low wind speed and no significant precipitation. By comparing toxin profiles and method sensitivity, it was found that dissolved toxins in seawater are more useful for early warning. These results have important implications for the effective monitoring and management of paralytic shellfish poisoning outbreaks.