Antirheumatic drug leflunomide attenuates atherosclerosis by regulating lipid metabolism and endothelial dysfunction via DHODH/AMPK signaling pathway.

The probability of cardiovascular events has been reported lower in rheumatoid arthritis (RA) patients treated with leflunomide. However, the anti-atherosclerotic and cardiovascular protective effects and metabolism of leflunomide are not explored. In this study, we assessed the potential benefits of leflunomide on atherosclerosis and revealed the underlying mechanism. ApoE-/- mice were fed a western diet (WD) alone or supplemented with leflunomide (20 mg/kg, oral gavage, once per day) for 12 weeks. Samples of the aorta, heart, liver, serum, and macrophages were collected. We found that leflunomide significantly reduced lesion size in both en-face aortas and aortic root in WD-fed ApoE-/- mice. Leflunomide also obviously improved dyslipidemia, reduced hepatic lipid content, and improved disorders of glucose and lipid metabolism in vivo. RNA-Seq results showed that leflunomide effectively regulated the genes' expression involved in the lipid metabolism pathway. Importantly, leflunomide significantly increased the phosphorylation levels of AMPKα and acetyl-CoA carboxylase (ACC) in vivo. Furthermore, leflunomide and its active metabolite teriflunomide suppressed lipid accumulation in free fatty acid (FFA)-induced AML12 cells and improved endothelial dysfunction in palmitic acid (PA)-induced HUVECs through activating AMPK signaling and inhibiting dihydroorotate dehydrogenase (DHODH) signaling pathway. We present evidence that leflunomide and teriflunomide ameliorate atherosclerosis by regulating lipid metabolism and endothelial dysfunction. Our findings suggest a promising use of antirheumatic small-molecule drugs leflunomide and teriflunomide for the treatment of atherosclerosis and related cardiovascular diseases (CVDs).

Chromomycins from soil-derived Streptomyces sp. inhibit the growth of human non-small cell lung cancer cells by targeting c-FLIP.

Three chromomycin derivatives, chromomycins A3 (1, CA3), A5 (2, CA5), and monodeacetylchromomycin A3 (3, MDA-CA3), were identified from the soil-derived Streptomyces sp. CGMCC 26516. A reinvestigation of the structure of CA5 is reported, of which the absolute configuration was unambiguously determined for the first time to be identical with that of CA3 based on nuclear magnetic resonance (NMR) data analysis as well as NMR and electronic circular dichroism calculations. Compounds 1-3 showed potent cytotoxicity against the non-small-cell lung cancer (NSCLC) cells (A549, H460, H157-c-FLIP, and H157-LacZ) and down-regulated the protein expression of c-FLIP in A549 cells. The IC50 values of chromomycins in H157-c-FLIP were higher than that in H157-LacZ. Furthermore, si-c-FLIP promoted anti-proliferation effect of chromomycins in NSCLC cells. In nude mice xenograft model, 1 and 2 both showed more potent inhibition on the growth of H157-lacZ xenografts than that of H157-c-FLIP xenografts. These results verify that c-FLIP mediates the anticancer effects of chromomycins in NSCLC.

Carrimycin inhibits coronavirus replication by decreasing the efficiency of programmed -1 ribosomal frameshifting through directly binding to the RNA pseudoknot of viral frameshift-stimulatory element.

The pandemic of SARS-CoV-2 worldwide with successive emerging variants urgently calls for small-molecule oral drugs with broad-spectrum antiviral activity. Here, we show that carrimycin, a new macrolide antibiotic in the clinic and an antiviral candidate for SARS-CoV-2 in phase III trials, decreases the efficiency of programmed -1 ribosomal frameshifting of coronaviruses and thus impedes viral replication in a broad-spectrum fashion. Carrimycin binds directly to the coronaviral frameshift-stimulatory element (FSE) RNA pseudoknot, interrupting the viral protein translation switch from ORF1a to ORF1b and thereby reducing the level of the core components of the viral replication and transcription complexes. Combined carrimycin with known viral replicase inhibitors yielded a synergistic inhibitory effect on coronaviruses. Because the FSE mechanism is essential in all coronaviruses, carrimycin could be a new broad-spectrum antiviral drug for human coronaviruses by directly targeting the conserved coronaviral FSE RNA. This finding may open a new direction in antiviral drug discovery for coronavirus variants.

A novel small-molecule PCSK9 inhibitor E28362 ameliorates hyperlipidemia and atherosclerosis.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the epidermal growth factor precursor homologous domain A (EGF-A) of low-density lipoprotein receptor (LDLR) in the liver and triggers the degradation of LDLR via the lysosomal pathway, consequently leading to an elevation in plasma LDL-C levels. Inhibiting PCSK9 prolongs the lifespan of LDLR and maintains cholesterol homeostasis in the body. Thus, PCSK9 is an innovative pharmacological target for treating hypercholesterolemia and atherosclerosis. In this study, we discovered that E28362 was a novel small-molecule PCSK9 inhibitor by conducting a virtual screening of a library containing 40,000 compounds. E28362 (5, 10, 20 µM) dose-dependently increased the protein levels of LDLR in both total protein and the membrane fraction in both HepG2 and AML12 cells, and enhanced the uptake of DiI-LDL in AML12 cells. MTT assay showed that E28362 up to 80 µM had no obvious toxicity in HepG2, AML12, and HEK293a cells. The effects of E28362 on hyperlipidemia and atherosclerosis were evaluated in three different animal models. In high-fat diet-fed golden hamsters, administration of E28362 (6.7, 20, 60 mg·kg-1·d-1, i.g.) for 4 weeks significantly reduced plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C) and PCSK9 levels, and reduced liver TC and TG contents. In Western diet-fed ApoE-/- mice (20, 60 mg·kg-1·d-1, i.g.) and human PCSK9 D374Y overexpression mice (60 mg·kg-1·d-1, i.g.), administration of E28362 for 12 weeks significantly decreased plasma LDL-C levels and the area of atherosclerotic lesions in en face aortas and aortic roots. Moreover, E28362 significantly increased the protein expression level of LDLR in the liver. We revealed that E28362 selectively bound to PCSK9 in HepG2 and AML12 cells, blocked the interaction between LDLR and PCSK9, and induced the degradation of PCSK9 through the ubiquitin-proteasome pathway, which finally resulted in increased LDLR protein levels. In conclusion, E28362 can block the interaction between PCSK9 and LDLR, induce the degradation of PCSK9, increase LDLR protein levels, and alleviate hyperlipidemia and atherosclerosis in three distinct animal models, suggesting that E28362 is a promising lead compound for the treatment of hyperlipidemia and atherosclerosis.

Hepatic Sirt6 activation abrogates acute liver failure.

Acute liver failure (ALF) is a deadly illness due to insufficient detoxification in liver induced by drugs, toxins, and other etiologies, and the effective treatment for ALF is very limited. Among the drug-induced ALF, acetaminophen (APAP) overdose is the most common cause. However, the molecular mechanisms underlying APAP hepatoxicity remain incompletely understood. Sirtuin 6 (Sirt6) is a stress responsive protein deacetylase and plays an important role in regulation of DNA repair, genomic stability, oxidative stress, and inflammation. Here, we report that genetic and pharmacological activation of Sirt6 protects against ALF in mice. We first observed that Sirt6 expression was significantly reduced in the liver tissues of human patients with ALF and mice treated with an overdose of APAP. Then we developed an inducible Sirt6 transgenic mice for Cre-mediated overexpression of the human Sirt6 gene in systemic (Sirt6-Tg) and hepatic-specific (Sirt6-HepTg) manners. Both Sirt6-Tg mice and Sirt6-HepTg mice exhibited the significant protection against APAP hepatoxicity. In contrast, hepatic-specific Sirt6 knockout mice exaggerated APAP-induced liver damages. Mechanistically, Sirt6 attenuated APAP-induced hepatocyte necrosis and apoptosis through downregulation of oxidative stress, inflammation, the stress-activated kinase JNK activation, and apoptotic caspase activation. Moreover, Sirt6 negatively modulated the level and activity of poly (ADP-ribose) polymerase 1 (PARP1) in APAP-treated mouse liver tissues. Importantly, the specific Sirt6 activator MDL-800 exhibited better therapeutic potential for APAP hepatoxicity than the current drug acetylcysteine. Furthermore, in the model of bile duct ligation induced ALF, hepatic Sirt6-KO exacerbated, but Sirt6-HepTg mitigated liver damage. Collectively, our results demonstrate that Sirt6 protects against ALF and suggest that targeting Sirt6 activation could be a new therapeutic strategy to alleviate ALF.

The novel small molecule E0924G dually regulates bone formation and bone resorption through activating the PPARδ signaling pathway to prevent bone loss in ovariectomized rats and senile mice.

Osteoporosis is particularly prevalent among postmenopausal women and the elderly. In the present study, we investigated the effect of the novel small molecule E0924G (N-(4-methoxy-pyridine-2-yl)-5-methylfuran-2-formamide) on osteoporosis. E0924G significantly increased the protein expression levels of osteoprotegerin (OPG) and runt-related transcription factor 2 (RUNX2), and thus significantly promoted osteogenesis in MC3T3-E1 cells. E0924G also significantly decreased osteoclast differentiation and inhibited bone resorption and F-actin ring formation in receptor activator of NF-κB ligand (RANKL)-induced osteoclasts from RAW264.7 macrophages. Importantly, oral administration of E0924G in both ovariectomized (OVX) rats and SAMP6 senile mice significantly increased bone mineral density and decreased bone loss compared to OVX controls or SAMR1 mice. Further mechanistic studies showed that E0924G could bind to and then activate peroxisome proliferator-activated receptor delta (PPARδ), and the pro-osteoblast effect and the inhibition of osteoclast differentiation induced by E0924G were significantly abolished when PPARδ was knocked down or inhibited. In conclusion, these data strongly suggest that E0924G has the potential to prevent OVX-induced and age-related osteoporosis by dual regulation of bone formation and bone resorption through activation of the PPARδ signaling pathway.

Trichostatin C Synergistically Interacts with DNMT Inhibitor to Induce Antineoplastic Effect via Inhibition of Axl in Bladder and Lung Cancer Cells.

Aberrant epigenetic modifications are fundamental contributors to the pathogenesis of various cancers. Consequently, targeting these aberrations with small molecules, such as histone deacetylase (HDAC) inhibitors and DNA methyltransferase (DNMT) inhibitors, presents a viable strategy for cancer therapy. The objective of this study is to assess the anti-cancer efficacy of trichostatin C (TSC), an analogue of trichostatin A sourced from the fermentation of Streptomyces sp. CPCC 203909. Our investigations reveal that TSC demonstrates potent activity against both human lung cancer and urothelial bladder cancer cell lines, with IC50 values in the low micromolar range. Moreover, TSC induces apoptosis mediated by caspase 3/7 and arrests the cell cycle at the G2/M phase. When combined with the DNMT inhibitor decitabine, TSC exhibits a synergistic anti-cancer effect. Additionally, protein analysis elucidates a significant reduction in the expression of the tyrosine kinase receptor Axl. Notably, elevated concentrations of TSC correlate with the up-regulation of the transcription factor forkhead box class O1 (FoxO1) and increased levels of the proapoptotic proteins Bim and p21. In conclusion, our findings suggest TSC as a promising anti-cancer agent with HDAC inhibitory activity. Furthermore, our results highlight the potential utility of TSC in combination with DNMT inhibitors for cancer treatment.

Establishment, optimization and validation of a fluorescence polarization-based high-throughput screening assay targeting cathepsin L inhibitors.

Cathepsin L (CTSL), a lysosomal cysteine proteinase, is primarily dedicated to the metabolic turnover of intracellular proteins. It is involved in various physiological processes and contributes to pathological conditions such as viral infection, tumor invasion and metastasis, inflammatory status, atherosclerosis, renal disease, diabetes, bone diseases, and other ailments. The coronavirus disease 2019 (COVID-19), with its rapid global spread and significant mortality, has been a worldwide epidemic since the late 2019s. Notably, CTSL plays a role in the processing of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, providing a potential avenue to block coronavirus host cell entry and thereby inhibit SARS-CoV-2 infection in humans. In this study, we have developed a novel method using fluorescence polarization (FP) for screening CTSL inhibitors in a high-throughput format. The optimized assay demonstrated its appropriateness for high-throughput screening (HTS) with a Z-factor of 0.9 in a 96-well format. Additionally, the IC50 of the known inhibitor, Z-Phe-Tyr-CHO, was determined to be 188.50 ± 46.88 nM. Upon screening over 2000 small molecules, we identified, for the first time, the anti-CTSL properties of a benzothiazoles derivative named IMB 8015. This work presents a novel high-throughput approach and its application in discovering and evaluating CTSL inhibitors.

A pan-PPAR agonist E17241 ameliorates hyperglycemia and diabetic dyslipidemia in KKAy mice via up-regulating ABCA1 in islet, liver, and white adipose tissue.

OBJECTIVE: Type 2 diabetes mellitus (T2DM) is a common chronic metabolic disease. Peroxisome proliferator-activated receptors (PPARs) play crucial roles in regulating glucolipid metabolism. Previous studies showed that E17241 could ameliorate atherosclerosis and lower fasting blood glucose levels in ApoE-/- mice. In this work, we investigated the role of E17241 in glycolipid metabolism in diabetic KKAy mice. APPROACH AND RESULTS: We confirmed that E17241 is a powerful pan-PPAR agonist with a potent agonistic activity on PPARγ, a high activity on PPARα, and a moderate activity on PPARδ. E17241 also significantly increased the protein expression of ATP-binding cassette transporter 1 (ABCA1), a crucial downstream target gene for PPARs. E17241 clearly lowered plasma glucose levels, improved OGTT and ITT, decreased islet cholesterol content, improved ß-cell function, and promoted insulin secretion in KKAy mice. Moreover, E17241 could significantly lower plasma total cholesterol and triglyceride levels, reduce liver lipid deposition, and improve the adipocyte hypertrophy and the inflammatory response in epididymal white adipose tissue. Further mechanistic studies indicated that E17241 boosts cholesterol efflux and insulin secretion in an ABCA1 dependent manner. RNA-seq and qRT-PCR analysis demonstrated that E17241 induced different expression of PPAR target genes in liver and adipose tissue differently from the PPARγ agonist rosiglitazone. In addition, E17241 treatment was also demonstrated to have an exhilarating cardiorenal benefits. CONCLUSIONS: Our results demonstrate that E17241 regulates glucolipid metabolism in KKAy diabetic mice while having cardiorenal benefits without inducing weight gain. It is a promising drug candidate for the treatment of T2DM.

Synthesis and structure-activity relationships of novel 14-membered 2-fluoro ketolides with structural modification at the C11 position.

A series of novel C11 substituted 14-membered 2-fluoro ketolides were synthesized and evaluated for their antibacterial activity against erythromycin-resistant and erythromycin-susceptible clinical isolates and strains from ATCC. The overall antibacterial spectra of the semi-synthetic antibiotics are similar to that of telithromycin (TEL) and most of them exhibited excellent activity against Gram-positive bacteria (S. epidermidis, S. pneumoniae, S. aureus) and several Gram-negative bacteria (M. catarrhalis, H. influenza). Compounds 11c, 11g, 11h, 11q, 12a, 12b, 12d and 12e displayed 4-16 fold more potency than TEL against all the tested erythromycin-resistant S. epidermidis strains and S. pneumonia SPN19-8 and SPN19-8. Compounds 11b, 11c, 11e, 11g, 11h, 11q, 12a, 12b and 12c showed at least 8 fold potency than TEL against erythromycin-resistant M. catarrhalis BCA19-5 and BCA19-6. Molecular docking suggested compound 12d oriented the macrolide ring and side chain similarly to solithromycin (SOL). Noticeably an additional hydrogen bond was observed between the Lys90 residue of ribosome protein L22 and the carbamate group at the C11 position, which might provide a rational explanation for the enhanced antibacterial activity of target compounds. Therefore this research would offer a new perspective for further structural optimization of the C11 side chain. Based on the results of antibacterial activity, cytotoxicity and structural diversity, 5 compounds (11a, 11b, 11h, 12d and 12i) were selected for the stability testing of human liver microsomes and compound 11a exhibited preferable metabolic stability.

Expression, purification, and biological activity evaluation of cathepsin L in mammalian cells.

Cathepsin L (CTSL) could cleave and activate SARS-CoV-2 Spike protein to promote viral entry, making it a hopeful therapeutic target for COVID-19 prevention and treatment. So CTSL inhibitors are considered to be a promising strategy to SARS-CoV-2 infection. CTSL has previously been expressed in inclusion body in Escherichia coli. In order to prepare CTSL with high purity and activity in soluble active form, we transformed HEK-293T cells with a recombinant mammalian expression plasmid. CTSL was purified to a purity about 95%, found to migrate at approximately 43 kDa and exhibited substrate specificity against Z-Phe-Arg-AMC with specific activity of no less than 85 081 U/mg, characteristic of active CTSL. Although eukaryotic purified CTSL is commercially available, our study for the first time reported the details of the expression, purification, and characterization of active, recombinant CTSL in eukaryocyte system, which laid an experimental foundation for the establishment of high-throughput screening model for anti-coronavirus drugs targeting CTSL.

Antimicrobial and Anti-inflammatory Cyclic Tetrapeptides from the Co-cultures of Two Marine-Derived Fungi.

Violaceotides B-E (1-4), four new cyclic tetrapeptides, along with seven known compounds, were identified from the sponge-associated Aspergillus insulicola IMB18-072 co-cultivated with the marine-derived Alternaria angustiovoidea IMB20-805. Their structures were elucidated by extensive analysis of spectroscopic data, including HRESIMS, 1D and 2D NMR, and MS/MS data. The absolute configurations were determined by the advanced Marfey's method. Compounds 2, 3, and violaceotide A (5) displayed selective antimicrobial activities against the aquatic pathogenic bacteria Edwardsiella tarda and E. ictaluri. In addition, compounds 1-5 showed inhibitory activities against the LPS-induced expression of the inflammatory mediator IL-6 in RAW264.7 cells at a concentration of 10 µM.

Unexpected Noremestrin with a Sulfur-Bearing 15-Membered Macrocyclic Lactone from Emericella sp. 1454.

Two previous unreported epipolythiodioxopiperazines of the emestrin family, namely, noremestrin A (1) and secoemestrin E (2), were successfully isolated from the fungal source Emericella sp. 1454. Employing comprehensive spectroscopic techniques, such as high-resolution electrospray ionization mass spectrometry, infrared, and nuclear magnetic resonance (NMR), along with NMR and electronic circular dichroism calculations, the chemical structures of compounds 1 and 2 were elucidated. Particularly noteworthy is the distinctive nature of noremestrin A, representing the inaugural instance of a noremestrin variant incorporating a sulfur-bearing 15-membered macrocyclic lactone moiety. Compounds 1 and 2 exhibited weak cytotoxic activities against the human chronic myelocytic leukemia cell lines MEG-01 and K562.

Anti-Biofilm Activity of Cocultimycin A against Candida albicans.

Candida albicans (C. albicans), the most common fungal pathogen, has the ability to form a biofilm, leading to enhanced virulence and antibiotic resistance. Cocultimycin A, a novel antifungal antibiotic isolated from the co-culture of two marine fungi, exhibited a potent inhibitory effect on planktonic C. albicans cells. This study aimed to evaluate the anti-biofilm activity of cocultimycin A against C. albicans and explore its underlying mechanism. Crystal violet staining showed that cocultimycin A remarkably inhibited biofilm formation in a dose-dependent manner and disrupted mature biofilms at higher concentrations. However, the metabolic activity of mature biofilms treated with lower concentrations of cocultimycin A significantly decreased when using the XTT reduction method. Cocultimycin A could inhibit yeast-to-hypha transition and mycelium formation of C. albicans colonies, which was observed through the use of a light microscope. Scanning electron microscopy revealed that biofilms treated with cocultimycin A were disrupted, yeast cells increased, and hypha cells decreased and significantly shortened. The adhesive ability of C. albicans cells treated with cocultimycin A to the medium and HOEC cells significantly decreased. Through the use of a qRT-PCR assay, the expression of multiple genes related to adhesion, hyphal formation and cell membrane changes in relation to biofilm cells treated with cocultimycin A. All these results suggested that cocultimycin A may be considered a potential novel molecule for treating and preventing biofilm-related C. albicans infections.

Erratum to "Identification of anti-Mycobacterium tuberculosis agents targeting the interaction of bacterial division proteins FtsZ and SepFe" [Acta Pharmaceutica Sinica B 13 (2023) 2056-2070].

[This corrects the article DOI: 10.1016/j.apsb.2023.01.022.].

SIRT1 Activator E1231 Alleviates Nonalcoholic Fatty Liver Disease by Regulating Lipid Metabolism.

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases. Silencing information regulator 1 (SIRT1) was demonstrated to modulate cholesterol and lipid metabolism in NAFLD. Here, a novel SIRT1 activator, E1231, was studied for its potential improvement effects on NAFLD. C57BL/6J mice were fed a high-fat and high-cholesterol diet (HFHC) for 40 weeks to create a NAFLD mouse model, and E1231 was administered by oral gavage (50 mg/kg body weight, once/day) for 4 weeks. Liver-related plasma biochemistry parameter tests, Oil Red O staining, and hematoxylin-eosin staining results showed that E1231 treatment ameliorated plasma dyslipidemia, plasma marker levels of liver damage (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), liver total cholesterol (TC) and triglycerides (TG) contents, and obviously decreased hepatic steatosis score and NAFLD Activity Score (NAS) in the NAFLD mouse model. Western blot results showed that E1231 treatment significantly regulated lipid-metabolism-related protein expression. In particular, E1231 treatment increased SIRT1, PGC-1α, and p-AMPKα protein expression but decreased ACC and SCD-1 protein expression. Additionally, in vitro studies demonstrated that E1231 inhibited lipid accumulation and improved mitochondrial function in free-fatty-acid-challenged hepatocytes, and required SIRT1 activation. In conclusion, this study illustrated that the SIRT1 activator E1231 alleviated HFHC-induced NAFLD development and improved liver injury by regulating the SIRT1-AMPKα pathway, and might be a promising candidate compound for NAFLD treatment.

Identification of anti-Mycobacterium tuberculosis agents targeting the interaction of bacterial division proteins FtsZ and SepFe.

Tuberculosis (TB) is one of the deadly diseases caused by Mycobacterium tuberculosis (Mtb), which presents a significant public health challenge. Treatment of TB relies on the combination of several anti-TB drugs to create shorter and safer regimens. Therefore, new anti-TB agents working by different mechanisms are urgently needed. FtsZ, a tubulin-like protein with GTPase activity, forms a dynamic Z-ring in cell division. Most of FtsZ inhibitors are designed to inhibit GTPase activity. In Mtb, the function of Z-ring is modulated by SepF, a FtsZ binding protein. The FtsZ/SepF interaction is essential for FtsZ bundling and localization at the site of division. Here, we established a yeast two-hybrid based screening system to identify inhibitors of FtsZ/SepF interaction in M. tuberculosis. Using this system, we found compound T0349 showing strong anti-Mtb activity but with low toxicity to other bacteria strains and mice. Moreover, we have demonstrated that T0349 binds specifically to SepF to block FtsZ/SepF interaction by GST pull-down, fluorescence polarization (FP), surface plasmon resonance (SPR) and CRISPRi knockdown assays. Furthermore, T0349 can inhibit bacterial cell division by inducing filamentation and abnormal septum. Our data demonstrated that FtsZ/SepF interaction is a promising anti-TB drug target for identifying agents with novel mechanisms.

Three new isocoumarin analogues from an endolichenic fungus Aspergillus flavus CPCC 400810.

Five isocoumarin derivatives including three new compounds, aspermarolides A-C (1-3), and two known analogues, 8-methoxyldiaporthin (4) and diaporthin (5) were obtained from the culture extract of Aspergillus flavus CPCC 400810. The structures of these compounds were elucidated by spectroscopic methods. The double bond geometry of 1 and 2 were assigned by the coupling constants. The absolute configuration of 3 was determined by electronic circular dichroism experiment. All compounds showed no cytotoxic activities against the two human cancer cells HepG2 and Hela.

Omicsynin B4 potently blocks coronavirus infection by inhibiting host proteases cathepsin L and TMPRSS2.

The emergence of SARS-CoV-2 variants represents a major threat to public health and requires identification of novel therapeutic agents to address the unmet medical needs. Small molecules impeding viral entry through inhibition of spike protein priming proteases could have potent antiviral effects against SARS-CoV-2 infection. Omicsynin B4, a pseudo-tetrapeptides identified from Streptomyces sp. 1647, has potent antiviral activity against influenza A viruses in our previous study. Here, we found omicsynin B4 exhibited broad-spectrum anti-coronavirus activity against HCoV-229E, HCoV-OC43 and SARS-CoV-2 prototype and its variants in multiple cell lines. Further investigations revealed omicsynin B4 blocked the viral entry and might be related to the inhibition of host proteases. SARS-CoV-2 spike protein mediated pseudovirus assay supported the inhibitory activity on viral entry of omicsynin B4 with a more potent inhibition of Omicron variant, especially when overexpression of human TMPRSS2. Moreover, omicsynin B4 exhibited superior inhibitory activity in the sub-nanomolar range against CTSL, and a sub-micromolar inhibition against TMPRSS2 in biochemical assays. The molecular docking analysis confirmed that omicsynin B4 fits well in the substrate binding sites and forms a covalent bond to Cys25 and Ser441 in CTSL and TMPRSS2, respectively. In conclusion, we found that omicsynin B4 may serve as a natural protease inhibitor for CTSL and TMPRSS2, blocking various coronavirus S protein-driven entry into cells. These results further highlight the potential of omicsynin B4 as an attractive candidate for broad-spectrum antiviral therapy that could rapidly respond to emerging variants of SARS-CoV-2.

Small molecules targeting Pin1 as potent anticancer drugs.

Background: Pin1 is a member of the evolutionarily conserved peptidyl-prolyl isomerase (PPIase) family of proteins. Following phosphorylation, Pin1-catalyzed prolyl-isomerization induces conformational changes, which serve to regulate the function of many phosphorylated proteins that play important roles during oncogenesis. Thus, the inhibition of Pin1 provides a unique means of disrupting oncogenic pathways and therefore represents an appealing target for novel anticancer therapies. Methods: As Pin1 is conserved between yeast and humans, we employed budding yeast to establish a high-throughput screening method for the primary screening of Pin1 inhibitors. This effort culminated in the identification of the compounds HWH8-33 and HWH8-36. Multifaceted approaches were taken to determine the inhibition profiles of these compounds against Pin1 activity in vitro and in vivo, including an isomerization assay, surface plasmon resonance (SPR) technology, virtual docking, MTT proliferation assay, western blotting, cell cycle analysis, apoptosis analysis, immunofluorescence analysis, wound healing, migration assay, and nude mouse assay. Results: In vitro, HWH8-33 and HWH8-36 could bind to purified Pin1 and inhibited its enzyme activity; showed inhibitory effects on cancer cell proliferation; led to G2/M phase arrest, dysregulated downstream protein expression, and apoptosis; and suppressed cancer cell migration. In vivo, HWH8-33 suppressed tumor growth in the xenograft mice after oral administration for 4 weeks, with no noticeable toxicity. Together, these results show the anticancer activity of HWH8-33 and HWH8-36 against Pin1 for the first time. Conclusion: In summary, we identified two hit compounds HWH8-33 and HWH8-36, which after further structure optimization have the potential to be developed as antitumor drugs.