Glycyrrhizic acid improves tacrolimus-induced renal injury by regulating autophagy.

Tacrolimus (TAC)-induced renal injury is detrimental to long-term kidney function, but a treatment medication is not available. Glycyrrhizic acid (GA) is an active ingredient in licorice widely used to treat kidney disease. Thus, this study explored the mechanisms of renoprotection by GA on TAC-induced renal injury. C57BL/6 mice were subjected daily to TAC or a combination of TAC and GA for 4 weeks, and then renal function, histopathology, and autophagy were assessed to examine the effect of GA on a renal injury. Next, Human kidney proximal tubular epithelial (HK-2) cells were pretreated with GA for 2 h and then treated with TAC for 24 h. The effect of GA on TAC-induced HK-2 cell injury was assessed by measuring cell viability, apoptosis, autophagy, and lysosomes. Mice exposed to TAC and treated with GA had significantly greater improvements in renal function and tubulointerstitial fibrosis in comparison to mice not treated with GA. In addition, fibrosis-related protein expression, including α-smooth muscle actin and fibronectin, decreased after GA treatment. GA treatment also relieved autophagic clearance in TAC-induced renal injury. Several in vitro studies found that TAC inhibited cell viability, autophagy, lysosomal acidification, and promoted apoptosis. However, these results were less pronounced with GA pretreatment. In addition, bafilomycin A1 (which inhibits lysosomal function) reduced the protective effect of GA, indicating that lysosomal function plays an important role in this effect. Our data suggest that GA improves lysosomal function and regulates autophagy to protect against TAC-induced renal injury.

Accelerated Dynamic Reconstruction in Metal-Organic Frameworks with Ligand Defects for Selective Electrooxidation of Amines to Azos Coupling with Hydrogen Production.

Electrosynthesis coupled hydrogen production (ESHP) mostly involves catalyst reconstruction in aqueous phase, but accurately identifying and controlling the process is still a challenge. Herein, we modulated the electronic structure and exposed unsaturated sites of metal-organic frameworks (MOFs) via ligand defect to promote the reconstruction of catalyst for azo electrosynthesis (ESA) coupled with hydrogen production overall reaction. The monolayer Ni-MOFs achieved 89.8 % Faraday efficiency and 90.8 % selectivity for the electrooxidation of 1-methyl-1H-pyrazol-3-amine (Pyr-NH2) to azo, and an 18.5-fold increase in H2 production compared to overall water splitting. Operando X-ray absorption fine spectroscopy (XAFS) and various in situ spectroscopy confirm that the ligand defect promotes the potential dependent dynamic reconstruction of Ni(OH)2 and NiOOH, and the reabsorption of ligand significantly lowers the energy barrier of rate-determining step (*Pyr-NH to *Pyr-N). This work provides theoretical guidance for modulation of electrocatalyst reconstruction to achieve highly selective ESHP.

Liraglutide abrogates nephrotoxic effects of chemotherapies.

Acute kidney injury (AKI) is a common clinical complication. Cisplatin (Cis) is an effective chemotherapeutic drug; however, its acute nephrotoxicity often limits its application. The role of liraglutide (Lir), an agonist of the glucagon-like peptide-1 receptor (GLP-1R), has recently attracted increasing attention beyond glycemic regulation. This study showed that Lir significantly ameliorated Cis-induced kidney dysfunction and renal damage. However, this renoprotective effect was partially abolished in GLP-1R knockout (GLP-1R-/-) mice. Furthermore, we synthesized Lir metabolites, GLP-1 (9-37) and GLP-1 (28-37), and found that they also exerted reno-protective effects that were not impaired in GLP-1R-/- mice. We also demonstrated that Lir and its metabolites reduced cisplatin-induced apoptosis in human renal tubular epithelial cells (HK-2). After silencing GLP-1R expression in HK-2 cells with small interfering ribose nucleic acid (siRNA), the protective effect of Lir on HK-2 cells was inhibited, while the protective effects of GLP-1 (9-37) and GLP-1 (28-37) were not affected. Additionally, we demonstrated that Lir and its metabolites inhibited Cis-induced high-mobility group box 1 (HMGB1) nuclear-cytoplasmic translocation and release, and reduced inflammatory cytokines and HMGB1 receptor expression. The exogenous use of recombinant HMGB1 (rHMGB1) dramatically weakened the protective effects of Lir and its metabolites. In conclusion, our study shows that Lir significantly attenuated Cis-induced AKI through GLP-1R dependent and independent pathways, mediated by inhibiting nuclear-cytoplasmic translocation and release of HMGB1. Lir and its metabolites may be effective drugs for treating cisplatin-induced nephrotoxicity.

Broadening horizons in mechanisms, management, and treatment of diabetic kidney disease.

Diabetic kidney disease (DKD) is the first cause of end-stage kidney disease in patients with diabetes and its prevalence is increasing worldwide. It encompasses histological alterations that mainly affect the glomerular filtration unit, which include thickening of the basement membrane, mesangial cell proliferation, endothelial alteration, and podocyte injury. These morphological abnormalities further result in a persistent increase of urinary albumin-to-creatinine ratio and in a reduction of the estimated glomerular filtration rate. Several molecular and cellular mechanisms have been recognized, up to date, as major players in mediating such clinical and histological features and many more are being under investigation. This review summarizes the most recent advances in understanding cell death mechanisms, intracellular signaling pathways and molecular effectors that play a role in the onset and progression of diabetic kidney damage. Some of those molecular and cellular mechanisms have been already successfully targeted in preclinical models of DKD and, in some cases, strategies have been tested in clinical trials. Finally, this report sheds light on the relevance of novel pathways that may become therapeutic targets for future applications in DKD.

eATP and autoimmune diabetes.

PURPOSE OF REVIEW: The purine nucleotide adenosine triphosphate (ATP) is released into extracellular spaces as extracellular ATP (eATP) as a consequence of cell injury or death and activates the purinergic receptors. Once released, eATP may facilitate T-lymphocyte activation and differentiation. The purpose of this review is to elucidate the role of ATP-mediated signaling in the immunological events related to type 1 diabetes (T1D). RECENT FINDINGS: T lymphocytes mediate immune response during the onset of T1D and promote pancreatic islet or whole pancreas rejection in transplantation. Recent data suggest a potential role for eATP in early steps of T1D onset and of allograft rejection. In different preclinical experimental models and clinical trials, several drugs targeting purinergic signaling have been employed to abrogate lymphocyte activation and differentiation, thus representing an achievable treatment to prevent/revert T1D or to induce long-term islet allograft function. SUMMARY: In preclinical and clinical settings, eATP-signaling inhibition induces immune tolerance in autoimmune disease and in allotransplantation. In this view, the purinergic system may represent a novel therapeutic target for auto- and allo-immunity.

Boosting Hydrogen Production via Selective Two-electron Mild Electrochemical Oxidation of Tetrahydroisoquinolines Completely to Dihydroisoquinolines.

Different from the previous study that biomass derivatives replace water oxidation for enhancing hydrogen production, we found that mild oxidation was more conductive to cathodic hydrogen production. In this study, maximum Faradaic efficiency (>99 %) and lower energy consumption for hydrogen production was achieved by precisely controlling the two-electron mild electrochemical oxidation of tetrahydroisoquinolines (THIQs) to dihydroisoquinolines (DHIQs) in place of the four-electron deep oxidation to isoquinolines (IQs). Moreover, the high value-added DHIQs were prepared from THIQs with high selectivity (>99 %) at the low potential of 1.36 V. Operando electrochemical Raman and density functional theory proved that the high selectivity was attributed to the regulable active species of NiOOH induced by the interaction of Co and Fe for preferentially breaking C-H bond rather than N-H of THIQs. This novel method provides important insight into efficient biomass-assisted hydrogen production.

Neuregulin-4 attenuates diabetic cardiomyopathy by regulating autophagy via the AMPK/mTOR signalling pathway.

BACKGROUND: Diabetic cardiomyopathy is characterized by left ventricle dysfunction, cardiomyocyte apoptosis, and interstitial fibrosis and is a serious complication of diabetes mellitus (DM). Autophagy is a mechanism that is essential for maintaining normal heart morphology and function, and its dysregulation can produce pathological effects on diabetic hearts. Neuregulin-4 (Nrg4) is an adipokine that exerts protective effects against metabolic disorders and insulin resistance. The aim of this study was to explore whether Nrg4 could ameliorate DM-induced myocardial injury by regulating autophagy. METHODS: Four weeks after the establishment of a model of type 1 diabetes in mice, the mice received Nrg4 treatment (with or without an autophagy inhibitor) for another 4 weeks. The cardiac functions, histological structures and cardiomyocyte apoptosis were investigated. Autophagy-related protein levels along with related signalling pathways that regulate autophagy were evaluated. In addition, the effects of Nrg4 on autophagy were also determined in cultured primary cardiomyocytes. RESULTS: Nrg4 alleviated myocardial injury both in vivo and in vitro. The autophagy level was decreased in type 1 diabetic mice, and Nrg4 intervention reactivated autophagy. Furthermore, Nrg4 intervention was found to activate autophagy via the AMPK/mTOR signalling pathway. Moreover, when autophagy was suppressed or the AMPK/mTOR pathway was inhibited, the beneficial effects of Nrg4 were diminished. CONCLUSION: Nrg4 intervention attenuated diabetic cardiomyopathy by promoting autophagy in type 1 diabetic mice. Additionally, Nrg4 induced autophagy via the AMPK/mTOR signalling pathway.

Pharmacological targeting macrophage phenotype via gut-kidney axis ameliorates renal fibrosis in mice.

Renal fibrosis is a non-negligible pathological change in chronic kidney disease (CKD). Increasing evidence indicates that macrophage and gut-kidney axis are correlated with CKD. In this study, we manifest that pharmacological modulating macrophage phenotype via gut-kidney axis is conducive to the alleviation of renal fibrosis. Employing wild-type male mice with unilateral ureteral obstruction (UUO), renal fibrosis was dramatically mitigated in mice treated with antibiotics. And antibiotics application restricted the synthesis of intestinal flora metabolite Trimethylamine N-Oxide (TMAO). However, a 1.3% choline diet enhanced fibrosis. Then we further examined macrophage phenotype through the gut-kidney axis. In in vivo and in vitro culture experiments, the mRNA expression of Nos2, Tnf-α, Il-6, and Il-1ß increased under TMAO stimulation. Curbing the NLRP3 inflammasome countered TMAO-induced M1 polarization in bone marrow-derived macrophages. This finding demonstrates that NLRP3 plays a critical part in macrophage polarization. Because of the declining M1 polarization trend in the early stage, M2 macrophages undoubtedly decreased in the tissues. Our results revealed that some metabolites could regulate macrophage phenotype, which matters the severity of renal fibrosis. Thus, pharmacological targeting macrophage phenotype via gut-kidney axis may be a different strategy to treat renal fibrosis.

EZH2 mitigates the cardioprotective effects of mesenchymal stem cell-secreted exosomes against infarction via HMGA2-mediated PI3K/AKT signaling.

BACKGROUND: Mesenchymal stem cell-derived exosomes (MSC-EXO) have emerged as novel therapeutic strategies for myocardial infarction (MI). However, many questions remain untouched and unanswered regarding their roles in myocardial fibrosis. This study aimed to probe the therapeutic effects of MSC-EXO on myocardial fibrosis after MI and possible mechanisms. METHODS: Myocardial tissues were obtained from MI rats, and myocardial cell viability, fibrosis, apoptosis, and epithelial-mesenchymal transition (EMT) were detected by immunohistochemistry, Masson's staining, TUNEL, and western blot. Bone marrow-derived MSCs and corresponding EXO were identified, and cardiac function were detected after treatment of MSC-EXO. Bioinformatics analysis and ChIP assay were conducted to detect the downstream genes of EZH2. EZH2 was upregulated alone or with HMGA2 overexpression in myocardial tissues of MI rats upon MSC-EXO treatment, and PI3K/AKT pathway activity in myocardial tissues was detected using western blot. RESULTS: The proliferative activity in myocardial tissues of MI rats was significantly decreased, along with accentuated fibrosis, increased collagen volume and EMT. MSC-EXO treatment resulted in partial restoration of cardiac function and reduced EZH2 expression in the myocardium of rats. EZH2 inhibited HMGA2 expression by increasing the H3K27me3 modification. PI3K/AKT pathway was altered under the influence of the EZH2/HMGA2 axis. EZH2 inhibited the effect of MSC-EXO on the recovery of cardiac function and accelerated fibrosis, while HMGA2 reversed the effect of EZH2 to reduce fibrosis and enhance cardiac function. CONCLUSION: MSC-EXO alleviated fibrosis in MI rats via inhibition of EZH2, whereas EZH2 inhibited HMGA2 expression and impaired the PI3K/AKT pathway.

A Machine Learning-Based Risk Prediction Model for Post-Traumatic Stress Disorder during the COVID-19 Pandemic.

Background and Objectives: The COVID-19 pandemic has caused global public panic, leading to severe mental illnesses, such as post-traumatic stress disorder (PTSD). This study aimed to establish a risk prediction model of PTSD based on a machine learning algorithm to provide a basis for the extensive assessment and prediction of the PTSD risk status in adults during a pandemic. Materials and Methods: Model indexes were screened based on the cognitive-phenomenological-transactional (CPT) theoretical model. During the study period (1 March to 15 March 2020), 2067 Chinese residents were recruited using Research Electronic Data Capture (REDCap). Socio-demographic characteristics, PTSD, depression, anxiety, social support, general self-efficacy, coping style, and other indicators were collected in order to establish a neural network model to predict and evaluate the risk of PTSD. Results: The research findings showed that 368 of the 2067 participants (17.8%) developed PTSD. The model correctly predicted 90.0% (262) of the outcomes. Receiver operating characteristic (ROC) curves and their associated area under the ROC curve (AUC) values suggested that the prediction model possessed an accurate discrimination ability. In addition, depression, anxiety, age, coping style, whether the participants had seen a doctor during the COVID-19 quarantine period, and self-efficacy were important indexes. Conclusions: The high prediction accuracy of the model, constructed based on a machine learning algorithm, indicates its applicability in screening the public mental health status during the COVID-19 pandemic quickly and effectively. This model could also predict and identify high-risk groups early to prevent the worsening of PTSD symptoms.

The clinical, pathological, and genetic characteristics of lipid storage myopathy in northern China.

BACKGROUND: The lipid storage myopathy (LSM) diagnosis is based on the patient's clinical manifestations and muscle pathology. However, when genetic testing is lacking, there is a high rate of misdiagnosis of the disease. This study aimed to investigate the clinical and pathological features of genetically diagnosed LSM in northern China, analyze genetic mutations' characteristics, and improve the LSM diagnostic rate. METHODS: Twenty patients with LSM diagnosed were collected; meanwhile, the clinical data, muscle samples, and routine pathological staining of muscle specimens were collected. The morphological changes of muscle fibers were observed under an optical microscope. RESULTS: Among the included patients, 18 cases had ETFDH (HGNC ID: 3483) mutations, and two had PNPLA2 mutations. Family pedigree verification was performed on three patients with heterozygous mutations in the ETFDH gene complex. Histopathological staining showed that all patients had fine vacuoles in the muscle fibers, and some of them merged to form fissures, and the lipid droplets increased in cells. After therapy, 18 patients were associated with a favorable prognosis, and two patients were ineffective with the treatment of neutral lipid storage myopathy (NLSDM) caused by PNPLA2 mutation. DISCUSSION: The clinical manifestations of LSM are complex and diverse, mainly manifested by proximal muscle weakness and exercise intolerance in the extremities. The pathological images of LSM muscles are abnormal storage of lipid droplets in muscle fibers, primarily involving type I fibers. The LSM patients were mainly multiple acyl-CoA dehydrogenase deficiency (MADD) caused by the ETFDH gene mutation. It is necessary to perform an accurate typing diagnosis of LSM.

Mutation at a new allele of the dysferlin gene causes Miyoshi myopathy: A case report.

Miyoshi myopathy (MM) is a rare autosomal recessive disorder caused by dysferlin (DYSF) gene mutation. Miyoshi myopathy-inducing mutation sites in the DYSF gene have been discovered worldwide. In the present study, a patient with progressive lower extremity weakness is reported, for which MM was diagnosed according to clinical manifestations, muscle biopsy, and immunohistochemistry. In addition, the DYSF gene of the patient and his parents was sequenced and analyzed and two heterozygous mutations of the DYSF gene (c.4756C> T and c.5316dupC) were discovered. The first mutation correlated with MM while the second was a new mutation. The patient was diagnosed with a compound heterozygous mutation. The mutation site is a new member of pathogenic MM gene mutations.

Mechanism of the salt activation of laccase Lac15.

Laccases (benzenediol: oxygen oxidoreductases, EC1.10.3.2) can oxidize various substrates, and those which are tolerant to and even activated by salts have attracted a lot of attention due to their application potential in certain industries. The mechanism of the salt activation of laccases is awaiting to be elucidated yet. Our previous study (Li, Xie et al. 2018) supposed that the salt activation of marine laccase Lac15 might be attributed to Cl- ion specifically binding to some local sites to interfere substrate binding and/or electron transfer. In this study, we found two sites whose mutations resulted in elimination of the salt activation of Lac15's activity towards catechol and dopamine respectively, and revealed that the mutations affected the activity by altering both Em and kcat, demonstrating the supposed mechanism. A model for the salt activation of laccases was accordingly proposed, albeit some details are to be elucidated.

Birt-Hogg-Dubé syndrome caused by a mutation of FLCN gene in a CVST patient: a case report.

Background: To our knowledge, this is the first report of patient with BHD syndrome caused by a novel mutation in the FLCN gene who developed a cerebral venous sinus thrombosis(CVST).Case presentation: A 62-year-old male patient with a history of hypertension and two case of spontaneous pneumothorax. He had a 1-month history of headache and was admitted to the hospital one day after the headache aggravated. The patient had a family history of BHD syndrome which was confirmed by FLCN gene sequencing. Sequencing analysis revealed a novel nonsense mutation (NM_144997; c.607A > T; p.Lys203Ter) in the FLCN gene exon 6 of the patient, which was proved to be a pathogenetic mutation by pedigree verification. BHD syndrome was finally definitive diagnosis. Low molecular weight heparin (21 days) was given for anticoagulant therapy before and after resection of renal tumor which is confirmed to be clear cell carcinoma in the kidney. After discharge, warfarin was given for anticoagulant therapy (6 months).Conclusions: There was no recurrence of CVST. And no recurrence of tumor and new renal tumor were found in renal MRI examination after 6 months.

Statistical coupling analysis uncovers sites crucial for the proton transfer in laccase Lac15.

Laccases (benzenediol: oxygen oxidoreductases, EC1.10.3.2) can oxidize wide range of compounds thus have great application potential in diverse industries. The catalytic mechanisms of laccases have been extensively studied, while the details of proton transfer remain to be fully elucidated. In this study, we tried to uncover the sites that are crucial for the proton transfer of microbial laccase Lac15. A residue near the trinuclear copper center, D396, was indicated by statistical coupling analysis (SCA) and structural alignment to be an important site like D93, which is conserved in laccases and believed crucial for the catalysis by facilitating proton transfer. A representative mutant at this site, D396A, similar to D93A, exhibited significantly impaired catalysis with the global structure and substrate binding slightly perturbed. The mutation resulted in stay of the intermediate I, which would accept a proton to proceed to next catalysis stage, suggesting D396 might play a critical role in the proton transfer. Our finding may help to completely elucidate the proton transfer mechanism in laccases.

Highly glycosylated CD147 promotes hemorrhagic transformation after rt-PA treatment in diabetes: a novel therapeutic target?

BACKGROUND: Diabetes is known to be a main risk factor of post-stroke hemorrhagic transformation following recombinant tissue plasminogen activator (rt-PA) therapy. However, the mechanism through which diabetes exacerbates hemorrhagic transformation is insufficiently understood. We aimed to verify that CD147, the extracellular matrix metalloproteinase (MMP) inducer, played a vital role in the progress. METHODS: We performed middle cerebral artery occlusion on diabetic and non-diabetic rats, with or without rt-PA treatment, and then compared the glycosylation level of CD147, caveolin-1, MMPs activities, and blood-brain barrier (BBB) permeability. In vitro, tunicamycin treatment and genetic tools were used to produce non-glycosylated and lowly glycosylated CD147. An endogenous glucagon-like peptide-1 receptor (GLP-1R) agonist was used to downregulate the glycosylation of CD147 in vivo. RESULTS: Compared with non-diabetic rats, diabetic rats expressed higher levels of highly glycosylated CD147 in endothelium and astrocytes following rt-PA treatment accompanied by higher activity of MMPs and BBB permeability, in the middle cerebral artery occlusion model. Caveolin-1 was also overexpressed and co-localized with CD147 in astrocytes and endothelium in diabetic rats. In vitro, advanced glycation end products increased the expression of highly glycosylated CD147 in astrocytes and endothelial cells. Downregulating the glycosylation of CD147 lowered the activity of MMPs and promoted the expression of tight junction proteins. The expression of caveolin-1 in endothelial cells and astrocytes was not inhibited by tunicamycin, which revealed that caveolin-1 was an upstream of CD147. In vivo, GLP-1R agonist downregulated the glycosylation of CD147 and further reduced the activity of MMPs and protected the BBB in diabetic rats. CONCLUSION: CD147 is essential for diabetes-associated rt-PA-induced hemorrhagic transformation, and downregulation of CD147 glycosylation is a promising therapy for neurovascular-unit repair after rt-PA treatment of patients with diabetes.

A case of surgically-associated anti GQ1b antibody syndrome accompanied by saccadic ping pong gaze.

BACKGROUND: Periodic alternating ping-pong gaze (PPG) is a rare disease with few reports. To our knowledge, there was no report on anti GQ1b antibody syndrome accompanied by PPG. This paper reported a case of anti GQ1b antibody syndrome with Bickerstaff's Encephalitis (BBE) overlapping classic Guillain-Barre Syndrome (GBS) after aortic valve replacement, accompanied by an excessive PPG in the course of diagnosis and treatment, this was indeed rarely. CASE PRESENTATION: A 55-year-old male patient was admitted to our hospital with intermittent chest tightness for 3 months, and his condition has worsened in the past 10 days. Aortic valve replacement was performed because of the existence of the moderate and severe stenosis of aortic valve. Horizontal movement of the eyeball was involuntarily slow. The eyeball hovered and returned from one side to the other horizontally for 3-4 s per cycle. In combination with the patient's typical clinical and laboratory tests, the final diagnosis was anti GQ1b antibody syndrome BBE combined with GBS, accompanied by saccadic ping pong gaze. Intravenous immunoglobulin (0.4 g/kg) was given for immunomodulation, methylprednisolone (1000 mg) therapy and symptomatic treatment were performed in the patient. CONCLUSIONS: The patients were discharged from hospital on the thirtieth day because of economic reasons. After 6 months of follow up, the patients left behind a lack of fluency in speech and limb mobility, but the basic life can be taken care of by himself.

Adolescent Hyperuricemia with Lipid Storage Myopathy: A Clinical Study.

BACKGROUND In this study, we investigated the clinical and pathological features of patients with lipid storage myopathy (LSM) complicated with hyperuricemia, to improve clinicians' understanding of metabolic multi-muscular disorder with metabolic disorders, and to reduce the risk of missed diagnosis of LSM. MATERIAL AND METHODS From January 2005 to December 2017, 8 patients underwent muscle biopsy and diagnosed by muscle pathology and genetic testing in our hospital. All 8 patients were in compliance with LSM diagnosis. We collected data on the patient's clinical performance, adjuvant examination, treatment, and outcomes to provide a comprehensive report and description of LSM patients with hyperuricemia. RESULTS All patients were diagnosed as having ETFDH gene mutations. The main clinical manifestations of patients were chronic limb and trunk weakness, limb numbness, and muscle pain. The serum creatine kinase (CK) values in all patients were higher than normal values. Electromyography showed 3 cases of simple myogenic damage and 3 cases of neurogenic injury. Hematuria metabolic screening showed that 2 patients had elevated glutaric aciduria, and 1 patient had elevated fatty acyl carnitine in the blood. All patients were given riboflavin treatment, and the clinical symptoms were significantly improved, and 3 patients returned to normal uric acid levels after treatment. Pathological staining showed an abnormal deposition of lipid droplets in muscle fibers. CONCLUSIONS If an adolescent hyperuricemia patient has abnormal limb weakness, exercise intolerance, and elevated serum CK values, clinicians need to be highly alert to the possibility of LSM. Early diagnosis and treatment of LSM should improve the clinical symptoms and quality of life and reduce complications.

Mechanism of salt-induced activity enhancement of a marine-derived laccase, Lac15.

Laccase (benzenediol: oxygen oxidoreductases, EC1.10.3.2) is a multi-copper oxidase capable of oxidizing a variety of phenolic and other aromatic organic compounds. The catalytic power of laccase makes it an attractive candidate for potential applications in many areas of industry including biodegradation of organic pollutants and synthesis of novel drugs. Most laccases are vulnerable to high salt and have limited applications. However, some laccases are not only tolerant to but also activated by certain concentrations of salt and thus have great application potential. The mechanisms of salt-induced activity enhancement of laccases are unclear as yet. In this study, we used dynamic light scattering, size exclusion chromatography, analytical ultracentrifugation, intrinsic fluorescence emission, circular dichroism, ultraviolet-visible light absorption, and an enzymatic assay to investigate the potential correlation between the structure and activity of the marine-derived laccase, Lac15, whose activity is promoted by low concentrations of NaCl. The results showed that low concentrations of NaCl exert little influence on the protein structure, which was partially folded in the absence of the salt; moreover, the partially folded rather than the fully folded state seemed to be favorable for enzyme activity, and this partially folded state was distinctive from the so-called 'molten globule' occasionally observed in active enzymes. More data indicated that salt might promote laccase activity through mechanisms involving perturbation of specific local sites rather than a change in global structure. Potential binding sites for chloride ions and their roles in enzyme activity promotion are proposed.

Ruthenium(II)-Catalyzed Redox-Neutral [3+2] Annulation of Indoles with Internal Alkynes via C-H Bond Activation: Accessing a Pyrroloindolone Scaffold.

Ru(II)-catalyzed redox-neutral [3+2] annulation reactions of N-ethoxycarbamoyl indoles and internal alkynes via C-H bond activation are reported. This method features a broad internal alkyne scope, including various aryl/alkyl-, alkyl/alkyl-, and diaryl-substituted alkynes, good to excellent regioselectivity, diverse functional group tolerance, and mild reaction conditions. The N-ethoxycarbamoyl directing group, temperature, CsOAc, and ruthenium catalyst proved to be crucial for conversion and high regioselectivity. Additionally, preliminary mechanistic experiments were conducted, and a possible mechanism was proposed.