Piezo1 channel exaggerates ferroptosis of nucleus pulposus cells by mediating mechanical stress-induced iron influx.

To date, several molecules have been found to facilitate iron influx, while the types of iron influx channels remain to be elucidated. Here, Piezo1 channel was identified as a key iron transporter in response to mechanical stress. Piezo1-mediated iron overload disturbed iron metabolism and exaggerated ferroptosis in nucleus pulposus cells (NPCs). Importantly, Piezo1-induced iron influx was independent of the transferrin receptor (TFRC), a well-recognized iron gatekeeper. Furthermore, pharmacological inactivation of Piezo1 profoundly reduced iron accumulation, alleviated mitochondrial ROS, and suppressed ferroptotic alterations in stimulation of mechanical stress. Moreover, conditional knockout of Piezo1 (Col2a1-CreERT Piezo1flox/flox) attenuated the mechanical injury-induced intervertebral disc degeneration (IVDD). Notably, the protective effect of Piezo1 deficiency in IVDD was dampened in Piezo1/Gpx4 conditional double knockout (cDKO) mice (Col2a1-CreERT Piezo1flox/flox/Gpx4flox/flox). These findings suggest that Piezo1 is a potential determinant of iron influx, indicating that the Piezo1-iron-ferroptosis axis might shed light on the treatment of mechanical stress-induced diseases.

Stabilization of MOF (KAT8) by USP10 promotes esophageal squamous cell carcinoma proliferation and metastasis through epigenetic activation of ANXA2/Wnt signaling.

Dysregulation of MOF (also known as MYST1, KAT8), a highly conserved H4K16 acetyltransferase, plays important roles in human cancers. However, its expression and function in esophageal squamous cell carcinoma (ESCC) remain unknown. Here, we report that MOF is highly expressed in ESCC tumors and predicts a worse prognosis. Depletion of MOF in ESCC significantly impedes tumor growth and metastasis both in vitro and in vivo, whereas ectopic expression of MOF but not catalytically inactive mutant (MOF-E350Q) promotes ESCC progression, suggesting that MOF acetyltransferase activity is crucial for its oncogenic activity. Further analysis reveals that USP10, a deubiquitinase highly expressed in ESCC, binds to and deubiquitinates MOF at lysine 410, which protects it from proteosome-dependent protein degradation. MOF stabilization by USP10 promotes H4K16ac enrichment in the ANXA2 promoter to stimulate ANXA2 transcription in a JUN-dependent manner, which subsequently activates Wnt/ß-Catenin signaling to facilitate ESCC progression. Our findings highlight a novel USP10/MOF/ANXA2 axis as a promising therapeutic target for ESCC.

Discovery of Biaryl Amide Derivatives as Potent, Selective, and Orally Bioavailable RORγt Agonists for Cancer Immunotherapy.

The master transcription factor receptor retinoic acid receptor-related orphan receptor γt (RORγt) regulates the differentiation of T-helper 17 (Th17) cells and the production of interleukin-17 (IL-17). Activation of RORγt+ T cells in the tumor microenvironment promotes immune infiltration to more effectively inhibit tumor growth. Therefore, RORγt agonists provide a reachable approach to cancer immunotherapy. Herein, a series of biaryl amide derivatives as novel RORγt agonists were designed, synthesized, and evaluated. Starting from the reported RORγt inverse agonist GSK805 (1), "functionality switching" and structure-based drug optimization led to the discovery of a promising RORγt agonist lead compound 14, which displayed potent and selective RORγt agonist activity and significantly improved metabolic stability. With excellent in vivo pharmacokinetic profiles, compound 14 demonstrated robust efficacy in preclinical tumor models of mouse B16F10 melanoma and LLC lung adenocarcinoma. Taken together, current studies indicate that 14 deserves further investigation as a potential lead RORγt agonist for cancer immunotherapy.

A Propensity Score-Matching Analysis: Robotic Thymectomy Through the Subxiphoid Has Advantages Over Video-Assisted Thymectomy Surgery.

Objective: The purpose of this article is to evaluate the security and effectiveness of subxiphoid and subcostal robot-assisted thoracoscopic thymectomy (S-RATT) and compare it with subxiphoid and subcostal video-assisted thoracoscopic thymectomy (S-VATT) in terms of short-term perioperative results and costs. Methods: A retrospective study was carried out on 62 individuals who had undergone successful complete thymectomy for anterior mediastinal disease using subxiphoid and subcostal arch approaches. Propensity score-matching analysis was utilized between the two groups, and the perioperative outcomes were compared. Results: The S-RATT group exhibited less intraoperative blood loss (20 ± 15.35 versus 69.55 ± 69.54, P < .001), lower levels of C-reactive protein (112.38 ± 68.08 versus 72.58 ± 42.62, P = .027), and lower postoperative pain scores (2.09 ± 1.54 versus 4.27 ± 1.28, P < .001). However, the hospitalization costs of patients in the S-VATT group were found to be lower than those in the S-RATT group (33,802.41 ± 8785.05 versus 49,977.53 ± 20,221.79, P < .001). Conclusions: S-RATT appears to be a viable and secure method for managing anterior mediastinal tumors.

Polyp-Canal Reconstruction Reveals Evolution Toward Complexity in Corals.

Modern scleractinian corals are classified into robust, complex, and basal clades through comparative molecular studies. However, only few morphological or biological criteria can systematically determine the evolutionary trajectories of these major scleractinian coral clades. Here, we obtained the structural information of 21 scleractinian coral species representing robust and complex clades: High-resolution micro-computed tomography was used to reconstruct the polyp-canal systems in their colonies and to visualize the dynamic polyp growth processes. We found that the emergence of mesh-like canals may distinguish representatives of complex and robust clades. The differences in polyp-canal connections suggest distinct evolutionary trajectories among coral species: The formation of the canal network promoted the development of more complex coral structures, and coral polyps within this network formed calices of very similar volume, following precise axial growth directions. The influence of individual polyps on the coral colony becomes less significant as coral structures become more complex, and coral species with more complicated polyp-canal systems occupied niches more efficiently. This work supplements current evolutionary studies on reef-building corals, providing insight for further studies on coral growth patterns.

Relaxin-Loaded Inhaled Porous Microspheres Inhibit Idiopathic Pulmonary Fibrosis and Improve Pulmonary Function Post-Bleomycin Challenges.

Idiopathic pulmonary fibrosis (IPF) causes worsening pulmonary function, and no effective treatment for the disease etiology is available now. Recombinant Human Relaxin-2 (RLX), a peptide agent with anti-remodeling and anti-fibrotic effects, is a promising biotherapeutic candidate for musculoskeletal fibrosis. However, due to its short circulating half-life, optimal efficacy requires continuous infusion or repeated injections. Here, we developed the porous microspheres loading RLX (RLX@PMs) and evaluated their therapeutic potential on IPF by aerosol inhalation. RLX@PMs have a large geometric diameter as RLX reservoirs for a long-term drug release, but smaller aerodynamic diameter due to their porous structures, which were beneficial for higher deposition in the deeper lungs. The results showed a prolonged release over 24 days, and the released drug maintained its peptide structure and activity. RLX@PMs protected mice from excessive collagen deposition, architectural distortion, and decreased compliance after a single inhalation administration in the bleomycin-induced pulmonary fibrosis model. Moreover, RLX@PMs showed better safety than frequent gavage administration of pirfenidone. We also found RLX-ameliorated human myofibroblast-induced collagen gel contraction and suppressed macrophage polarization to the M2 type, which may be the reason for reversing fibrosis. Hence, RLX@PMs represent a novel strategy for the treatment of IPF and suggest clinical translational potential.

Discovery of novel BTK PROTACs with improved metabolic stability via linker rigidification strategy.

Bruton's Tyrosine Kinase (BTK) functions as a key regulator of B-cell receptor (BCR) signaling pathway, which is frequently hyperactivated in a variety of lymphoma cancers. Using Proteolysis Targeting Chimera (PROTAC) technology, we have recently discovered a highly potent ARQ-531-derived BTK PROTAC 6e, inducing effective degradation of both wild type (WT) and C481S mutant BTK proteins. However, the poor metabolic stability of PROTAC 6e have limited its further in vivo studies. Herein, we present our structure-activity relationship (SAR) studies on modifying PROTAC 6e using linker rigidification strategy to identify a novel cereblon (CRBN)-recruiting compound 3e that induced BTK degradation in a concentration-dependent manner but had no effect on reducing the level of CRBN neo-substrates. Moreover, compound 3e suppressed the cell growth more potently than the small molecule inhibitors ibrutinib and ARQ-531 in several cells. Furthermore, compound 3e with the rigid linker displayed a significantly improved metabolic stability profile with the T1/2 increased to more than 145 min. Overall, we discovered a highly potent and selective BTK PROTAC lead compound 3e, which could be further optimized as potential BTK degradation therapy for BTK-associated human cancers and diseases.

Design, synthesis and bioactivity evaluations of 8-substituted-quinoline-2-carboxamide derivatives as novel histone deacetylase (HDAC) inhibitors.

The inhibition of histone deacetylases (HDACs) has been considered a promising therapeutic strategy for treatment of many diseases, especially cancer. In the current study, a series of 8-substituted quinoline-2-carboxamide derivatives were designed and synthesized as potent HDAC inhibitors. The most potent compound 21 g (IC50 = 0.050 µM) exhibited 3-fold greater HDAC inhibitory activity compared to the known HDAC inhibitor Vorinostat (IC50 = 0.137 µM). Additionally, compound 21g exhibited low toxicity against normal cells(IC50 in HUVEC cell > 50 µM) and showed good liver microsomal stability, therefore, may serve as a new lead compound for further development.

Phylogenetic diversity of eastern Asia-eastern North America disjunct plants is mainly associated with divergence time.

The underlying causes of biodiversity disparities among geographic regions have long been a fundamental theme in ecology and evolution. However, the patterns of phylogenetic diversity (PD) and phylogenetic beta diversity (PBD) of congeners that are disjunctly distributed between eastern Asia-eastern North America (EA-ENA disjuncts) and their associated factors remain unknown. Here we investigated the standardized effect size of PD (SES-PD), PBD, and potentially associated factors in 11 natural mixed forest sites (five in EA and six in ENA) where abundant EA-ENA disjuncts occur. We found that the disjuncts in ENA possessed higher SES-PD than those in EA at the continental scale (1.96 vs -1.12), even though the number of disjunct species in ENA is much lower than in EA (128 vs 263). SES-PD of the EA-ENA disjuncts tended to decrease with increasing latitude in 11 sites. The latitudinal diversity gradient of SES-PD was stronger in EA sites than in ENA sites. Based on the unweighted unique fraction metric (UniFrac) distance and the phylogenetic community dissimilarity, PBD showed that the two northern sites in EA were more similar to the six-site ENA group than to the remaining southern EA sites. Based on the standardized effect size of mean pairwise distances (SES-MPD), nine of eleven studied sites showed a neutral community structure (-1.96 ≤ SES-MPD ≤ 1.96). Both Pearson's r and structural equation modeling suggested that SES-PD of the EA-ENA disjuncts was mostly associated with mean divergence time. Moreover, SES-PD of the EA-ENA disjuncts was positively correlated with temperature-related climatic factors, although negatively correlated with mean diversification rate and community structure. By applying approaches from phylogenetics and community ecology, our work sheds light on historical patterns of the EA-ENA disjunction and paves the way for further research.

Contrast-enhanced ultrasound demonstrates greater adjuvant potential: past, current status, and future applications in Hepatocellular carcinoma early diagnosis.

Hepatocellular carcinoma (HCC) has an atypical onset of clinical symptoms and a rapid tumor progression. The majority of patients with HCC are already in the late stages of the disease when they are diagnosed, limiting them to the best available treatments. Contrast-enhanced ultrasound (CEUS) has achieved significant advances in the diagnosis of HCC, including the detection of small lesions, the investigation of more beneficial contrast agents, and the use of CEUS-based radiomics. The purpose of this review is to discuss the relevant research and future challenges of CEUS in the early detection of HCC, to advise more accurate therapy.

Optimization of carbazole carboxamide RORγt agonists: Challenges in improving the metabolic stability and maintaining the agonistic activity.

Based on two previously discovered carbazole carboxamide retinoic acid receptor-related orphan receptor-γt (RORγt) agonists 6 and 7 (t1/2 = 8.7 min and 16.4 min in mouse liver microsome, respectively), new carbazole carboxamides were designed and synthesized according to the molecular mechanism of action (MOA) and metabolic site analysis with the aim of identifying novel RORγt agonists with optimal pharmacological and metabolic profiles. By modifying the "agonist lock" touching substitutions on carbazole ring, introducing heteroatoms into different parts of the molecule and attaching a side chain to the sulfonyl benzyl moiety, several potent RORγt agonists were identified with greatly improved metabolic stability. Best overall properties were achieved in compound (R)-10f with high agonistic activities in RORγt dual FRET (EC50 = 15.6 nM) and Gal4 reporter gene (EC50 = 141 nM) assays and greatly improved metabolic stability (t1/2 > 145 min) in mouse liver microsome. Besides, the binding modes of (R)-10f and (S)-10f in RORγt ligand binding domain (LBD) were also studied. Altogether, the optimization of carbazole carboxamides led to the discovery of (R)-10f as a potential small molecule therapeutics for cancer immunotherapy.

Delivery of coenzyme Q10 loaded micelle targets mitochondrial ROS and enhances efficiency of mesenchymal stem cell therapy in intervertebral disc degeneration.

Stem cell transplantation has been proved a promising therapeutic instrument in intervertebral disc degeneration (IVDD). However, the elevation of oxidative stress in the degenerated region impairs the efficiency of mesenchymal stem cells (BMSCs) transplantation treatment via exaggeration of mitochondrial ROS and promotion of BMSCs apoptosis. Herein, we applied an emulsion-confined assembly method to encapsulate Coenzyme Q10 (Co-Q10), a promising hydrophobic antioxidant which targets mitochondria ROS, into the lecithin micelles, which renders the insoluble Co-Q10 dispersible in water as stable colloids. These micelles are injectable, which displayed efficient ability to facilitate Co-Q10 to get into BMSCs in vitro, and exhibited prolonged release of Co-Q10 in intervertebral disc tissue of animal models. Compared to mere use of Co-Q10, the Co-Q10 loaded micelle possessed better bioactivities, which elevated the viability, restored mitochondrial structure as well as function, and enhanced production of ECM components in rat BMSCs. Moreover, it is demonstrated that the injection of this micelle with BMSCs retained disc height and alleviated IVDD in a rat needle puncture model. Therefore, these Co-Q10 loaded micelles play a protective role in cell survival and differentiation through antagonizing mitochondrial ROS, and might be a potential therapeutic agent for IVDD.

A resample-replace lasso procedure for combining high-dimensional markers with limit of detection.

In disease screening, a biomarker combination developed by combining multiple markers tends to have a higher sensitivity than an individual marker. Parametric methods for marker combination rely on the inverse of covariance matrices, which is often a non-trivial problem for high-dimensional data generated by modern high-throughput technologies. Additionally, another common problem in disease diagnosis is the existence of limit of detection (LOD) for an instrument - that is, when a biomarker's value falls below the limit, it cannot be observed and is assigned an NA value. To handle these two challenges in combining high-dimensional biomarkers with the presence of LOD, we propose a resample-replace lasso procedure. We first impute the values below LOD and then use the graphical lasso method to estimate the means and precision matrices for the high-dimensional biomarkers. The simulation results show that our method outperforms alternative methods such as either substitute NA values with LOD values or remove observations that have NA values. A real case analysis on a protein profiling study of glioblastoma patients on their survival status indicates that the biomarker combination obtained through the proposed method is more accurate in distinguishing between two groups.

The Classification of Axial Deformity in Patients with Basilar Invagination.

OBJECTIVE: To summarize the variation types of the axis in patients with basilar invagination (BI), then propose a classification scheme of the axis deformity. METHODS: From December 2013 to September 2020, 92 patients (male 42, female 50) who were diagnosed with BI were studied retrospectively. Based on the imaging data of CT, the width and height of the axis pedicle and the sagittal diameter of the lateral mass were measured in each patient. According to the development of axis pedicle and lateral mass, the types of axis variation were summarized, and then the classification scheme of axis deformity was put forward. RESULTS: All cases were analyzed and axis deformities were divided into four types. Type I: the axis is basically normal (53 cases, 57.6%). Type II: axis lateral mass is dysplasia (eight cases, 8.7%), which includes two subtypes: type IIA, the axis unilateral lateral mass is dysplasia (three cases); type IIB, the axis bilateral lateral masses are all dysplasia (five cases). Type III: axis pedicle is dysplasia (11 cases, 12%), which is subdivided into two subtypes: type IIIA, the axis unilateral pedicle is dysplasia (six cases); type IIIB, the axis bilateral pedicles are all dysplasia (five cases). Type IV: axis pedicle and lateral mass are all dysplasia (20 cases, 21.7%), this type contains the following four subtypes: type IVA, the unilateral axis pedicle and unilateral lateral mass (contralateral or ipsilateral) are all hypoplasia (four cases); type IVB, the unilateral axis pedicle and bilateral lateral masses are all hypoplasia (five cases); type IVC, the bilateral axis pedicles and unilateral lateral mass are all dysplasia (seven cases); type IVD, the bilateral axis pedicles and bilateral lateral masses are all dysplasia (four cases). The left and right abnormal lateral mass sagittal diameter (Type II) was (7.23 ± 1.39) mm and (5.96 ± 1.37) mm, respectively, the left and right abnormal pedicle width (Type III) was (2.61 ± 1.01) mm and (3.23 ± 0.66) mm, respectively, left and right abnormal pedicle height (Type III) was (5.43 ± 2.19) mm and (4.92 ± 1.76) mm, respectively. Moreover, the classification scheme has good repeatability and credibility. CONCLUSIONS: The classification about axis deformity could provide personalized guidance for axis screw placement in the BI and other upper cervical surgery, and axis screw placement errors would be effectively avoided.

Application of Computer-Based Simulation Teaching Combined with PBL in Colorectal Tumor Hemorrhage.

Objective: This paper aims to explore the use of computer-based simulation teaching combined with PBL in colorectal tumor bleeding. Methods: The outpatient department organized 21 nursing staffs to conduct computer simulation combined with PBL teaching, compared emergency theory and skill scores, and investigated the recognition of computer simulation teaching combined with PBL. Results: The scores of theoretical knowledge examination before training were (84.31 ± 6.39) and (92.59 ± 2.93) after training; the scores of treatment skills examination were (85.69 ± 6.15) and (95.43 ± 2.88) after training; the scores of comprehensive treatment skills before training were (76.6 ± 6.31) and (91.43 ± 2.3) after training. The results of the questionnaires showed that the nurses were more agreeable to the new teaching methods and were able to complete the tasks in strict accordance with the requirements, ultimately achieving a level of satisfaction with their progress. Conclusion: Computer simulation teaching combined with PBL can deepen general practitioners' understanding of knowledge, improve practical ability, and provide a clinical basis for improving patient resuscitation in specialized oncology hospitals.

Cortistatin attenuates titanium particle-induced osteolysis through regulation of TNFR1-ROS-caspase-3 signaling in osteoblasts.

Aseptic loosening is a major complication of prosthetic joint surgery and is associated with impaired osteoblast homeostasis. Cortistatin (CST) is a neuropeptide that protects against inflammatory conditions. In this study, we found that expression of CST was diminished in patients with prosthetic joint loosening and in titanium (Ti) particle-induced animal models. A Ti particle-induced calvarial osteolysis model was established in wild-type and CST gene knockout mice; CST deficiency enhanced, while exogenously added CST attenuated, the severity of Ti particle-mediated osteolysis. CST protected against inflammation as well as apoptosis and maintained the osteogenic function of MC3T3-E1 osteoblasts upon stimulation with Ti particles. Furthermore, CST antagonized reactive oxygen species production and suppressed caspase-3-associated apoptosis mediated by Ti particles in osteoblasts. Additionally, CST protects against Ti particle-induced osteolysis through tumor necrosis factor receptor 1. Taken together, CST might provide a therapeutic strategy for wear debris-induced inflammatory osteolysis.

Salubrinal protects against inflammatory response in macrophage and attenuates psoriasiform skin inflammation by antagonizing NF-κB signaling pathway.

Psoriasiform skin inflammation is the common chronic skin inflammatory disease with no effective clinical therapy. Salubrinal is a multifunctional molecule playing a protective role in several conditions. Recently, studies have reported that Salubrinal is a potential therapeutic agent for inflammatory diseases. However, the protective role of Salubrinal in psoriasis-like skin inflammation remains unknown. In this article, imiquimod (IMQ)-induced psoriasis models were established in wild-type mice to explore the role of Salubrinal in the development of psoriasis. As a result, the IMQ-induced mouse models exhibited typical skin inflammation, which was alleviated by the administration of Salubrinal. Furthermore, RAW264.7 macrophage was stimulated with Lipopolysaccharide(LPS) in the presence or absence of Salubrinal. LPS stimulation elevated the expression of various inflammatory biomarkers, while the administration of Salubrinal abolished the function of LPS in RAW264.7 macrophages. In addition, the activation of the nuclear factor-kappa B (NF-κB) signaling pathway in both the LPS-stimulated RAW264.7 macrophage and psoriasis mouse models was antagonized by the administration of Salubrinal. Collectively, Salubrinal might be considered as a promising therapeutic agent for psoriasis-like skin inflammation.

Smokers' Likelihood to Engage With Information and Misinformation on Twitter About the Relative Harms of e-Cigarette Use: Results From a Randomized Controlled Trial.

BACKGROUND: Information and misinformation on the internet about e-cigarette harms may increase smokers' misperceptions of e-cigarettes. There is limited research on smokers' engagement with information and misinformation about e-cigarettes on social media. OBJECTIVE: This study assessed smokers' likelihood to engage with-defined as replying, retweeting, liking, and sharing-tweets that contain information and misinformation and uncertainty about the harms of e-cigarettes. METHODS: We conducted a web-based randomized controlled trial among 2400 UK and US adult smokers who did not vape in the past 30 days. Participants were randomly assigned to view four tweets in one of four conditions: (1) e-cigarettes are as harmful or more harmful than smoking, (2) e-cigarettes are completely harmless, (3) uncertainty about e-cigarette harms, or (4) control (physical activity). The outcome measure was participants' likelihood of engaging with tweets, which comprised the sum of whether they would reply, retweet, like, and share each tweet. We fitted Poisson regression models to predict the likelihood of engagement with tweets among 974 Twitter users and 1287 non-Twitter social media users, adjusting for covariates and stratified by UK and US participants. RESULTS: Among Twitter users, participants were more likely to engage with tweets in condition 1 (e-cigarettes are as harmful or more harmful than smoking) than in condition 2 (e-cigarettes are completely harmless). Among other social media users, participants were more likely to likely to engage with tweets in condition 1 than in conditions 2 and 3 (e-cigarettes are completely harmless and uncertainty about e-cigarette harms). CONCLUSIONS: Tweets stating information and misinformation that e-cigarettes were as harmful or more harmful than smoking regular cigarettes may receive higher engagement than tweets indicating e-cigarettes were completely harmless. TRIAL REGISTRATION: International Standard Randomized Controlled Trial Number (ISRCTN) 16082420; https://doi.org/10.1186/ISRCTN16082420.

Learning curve for minimally invasive oesophagectomy of oesophageal cancer and survival analysis.

PURPOSE: Minimally invasive oesophagectomy is a technically demanding procedure, and the learning curve for this procedure should be explored. A survival analysis should also be performed. METHODS: A total of 214 consecutive patients who underwent minimally invasive oesophagectomy were retrospectively reviewed. To evaluate the development of thoracoscopic-laparoscopic oesophagectomy and compare mature minimally invasive oesophagectomy and open oesophagectomy, we comprehensively studied the clinical and surgical parameters. The cumulative sum (CUSUM) plot was used to evaluate the learning curve for systemic lymphadenectomy. Cox proportional hazards regression analysis was performed to explore the clinical factors affecting survival. RESULTS: The bleeding volume, operation time, and postoperative mortality within 3 months significantly decreased after 20 patients. The rise point for node dissection was visually determined to occur at patient 57 in the CUSUM plots. Patients who underwent mature thoracoscopic-laparoscopic oesophagectomy had better surgical data and short-term benefits than patients who underwent an open procedure. Cox proportional hazards regression analysis showed that the maximum diameter of the tumour cross-sectional area and the number of positive nodes significantly influenced survival. CONCLUSIONS: The results suggest that thoracoscopic-laparoscopic oesophagectomy has short-term benefits. There was no evidence that it was associated with a significantly better prognosis for patients with oesophageal cancer. ClinicalTrials Gov ID: NCT04217239; January 2, 2020 retrospectively registered.

Effects of brief exposure to misinformation about e-cigarette harms on twitter: a randomised controlled experiment.

OBJECTIVES: To assess the effect of exposure to misinformation about e-cigarette harms found on Twitter on adult current smokers' intention to quit smoking cigarettes, intention to purchase e-cigarettes and perceived relative harm of e-cigarettes compared with regular cigarettes. SETTING: An online randomised controlled experiment conducted in November 2019 among USA and UK current smokers. PARTICIPANTS: 2400 adult current smokers aged ≥18 years who were not current e-cigarette users recruited from an online panel. Participants' were randomised in a 1:1:1:1 ratio using a least-fill randomiser function. INTERVENTIONS: Viewing 4 tweets in random order within one of four conditions: (1) e-cigarettes are just as or more harmful than smoking, (2) e-cigarettes are completely harmless, (3) e-cigarette harms are uncertain, and (4) a control condition of tweets about physical activity. PRIMARY OUTCOMES MEASURES: Self-reported post-test intention to quit smoking cigarettes, intention to purchase e-cigarettes, and perceived relative harm of e-cigarettes compared with smoking. RESULTS: Among US and UK participants, after controlling for baseline measures of the outcome, exposure to tweets that e-cigarettes are as or more harmful than smoking versus control was associated with lower post-test intention to purchase e-cigarettes (ß=-0.339, 95% CI -0.487 to -0.191, p<0.001) and increased post-test perceived relative harm of e-cigarettes (ß=0.341, 95% CI 0.273 to 0.410, p<0.001). Among US smokers, exposure to tweets that e-cigarettes are completely harmless was associated with higher post-test intention to purchase e-cigarettes (ß=0.229, 95% CI 0.002 to 0.456, p=0.048) and lower post-test perceived relative harm of e-cigarettes (ß=-0.154, 95% CI -0.258 to -0.050, p=0.004). CONCLUSIONS: US and UK adult current smokers may be deterred from considering using e-cigarettes after brief exposure to tweets that e-cigarettes were just as or more harmful than smoking. Conversely, US adult current smokers may be encouraged to use e-cigarettes after exposure to tweets that e-cigarettes are completely harmless. These findings suggest that misinformation about e-cigarette harms may influence some adult smokers' decisions to consider using e-cigarettes. TRIAL REGISTRATION NUMBER: ISRCTN16082420.