Discovery of 5-Azaquinoxaline Derivatives as Potent and Orally Bioavailable Allosteric SHP2 Inhibitors.

SHP2 has emerged as an important target for oncology small-molecule drug discovery. As a nonreceptor tyrosine phosphatase within the MAPK pathway, it has been shown to control cell growth, differentiation, and oncogenic transformation. We used structure-based design to find a novel class of potent and orally bioavailable SHP2 inhibitors. Our efforts led to the discovery of the 5-azaquinoxaline as a new core for developing this class of compounds. Optimization of the potency and properties of this scaffold generated compound 30, that exhibited potent in vitro SHP2 inhibition and showed excellent in vivo efficacy and pharmacokinetic profile.

SHP2 Inhibition Sensitizes Diverse Oncogene-Addicted Solid Tumors to Re-treatment with Targeted Therapy.

Rationally targeted therapies have transformed cancer treatment, but many patients develop resistance through bypass signaling pathway activation. PF-07284892 (ARRY-558) is an allosteric SHP2 inhibitor designed to overcome bypass-signaling-mediated resistance when combined with inhibitors of various oncogenic drivers. Activity in this setting was confirmed in diverse tumor models. Patients with ALK fusion-positive lung cancer, BRAFV600E-mutant colorectal cancer, KRASG12D-mutant ovarian cancer, and ROS1 fusion-positive pancreatic cancer who previously developed targeted therapy resistance were treated with PF-07284892 on the first dose level of a first-in-human clinical trial. After progression on PF-07284892 monotherapy, a novel study design allowed the addition of oncogene-directed targeted therapy that had previously failed. Combination therapy led to rapid tumor and circulating tumor DNA (ctDNA) responses and extended the duration of overall clinical benefit. SIGNIFICANCE: PF-07284892-targeted therapy combinations overcame bypass-signaling-mediated resistance in a clinical setting in which neither component was active on its own. This provides proof of concept of the utility of SHP2 inhibitors in overcoming resistance to diverse targeted therapies and provides a paradigm for accelerated testing of novel drug combinations early in clinical development. See related commentary by Hernando-Calvo and Garralda, p. 1762. This article is highlighted in the In This Issue feature, p. 1749.

Estimated Prevalence and Clinical Manifestations of UBA1 Variants Associated With VEXAS Syndrome in a Clinical Population.

Importance: VEXAS (vacuoles, E1-ubiquitin-activating enzyme, X-linked, autoinflammatory, somatic) syndrome is a disease with rheumatologic and hematologic features caused by somatic variants in UBA1. Pathogenic variants are associated with a broad spectrum of clinical manifestations. Knowledge of prevalence, penetrance, and clinical characteristics of this disease have been limited by ascertainment biases based on known phenotypes. Objective: To determine the prevalence of pathogenic variants in UBA1 and associated clinical manifestations in an unselected population using a genomic ascertainment approach. Design, Setting, and Participants: This retrospective observational study evaluated UBA1 variants in exome data from 163 096 participants within the Geisinger MyCode Community Health Initiative. Clinical phenotypes were determined from Geisinger electronic health record data from January 1, 1996, to January 1, 2022. Exposures: Exome sequencing was performed. Main Outcomes and Measures: Outcome measures included prevalence of somatic UBA1 variation; presence of rheumatologic, hematologic, pulmonary, dermatologic, and other findings in individuals with somatic UBA1 variation on review of the electronic health record; review of laboratory data; bone marrow biopsy pathology analysis; and in vitro enzymatic assays. Results: In 163 096 participants (mean age, 52.8 years; 94% White; 61% women), 11 individuals harbored likely somatic variants at known pathogenic UBA1 positions, with 11 of 11 (100%) having clinical manifestations consistent with VEXAS syndrome (9 male, 2 female). A total of 5 of 11 individuals (45%) did not meet criteria for rheumatologic and/or hematologic diagnoses previously associated with VEXAS syndrome; however, all individuals had anemia (hemoglobin: mean, 7.8 g/dL; median, 7.5 g/dL), which was mostly macrocytic (10/11 [91%]) with concomitant thrombocytopenia (10/11 [91%]). Among the 11 patients identified, there was a pathogenic variant in 1 male participant prior to onset of VEXAS-related signs or symptoms and 2 female participants had disease with heterozygous variants. A previously unreported UBA1 variant (c.1861A>T; p.Ser621Cys) was found in a symptomatic patient, with in vitro data supporting a catalytic defect and pathogenicity. Together, disease-causing UBA1 variants were found in 1 in 13 591 unrelated individuals (95% CI, 1:7775-1:23 758), 1 in 4269 men older than 50 years (95% CI, 1:2319-1:7859), and 1 in 26 238 women older than 50 years (95% CI, 1:7196-1:147 669). Conclusions and Relevance: This study provides an estimate of the prevalence and a description of the clinical manifestations of UBA1 variants associated with VEXAS syndrome within a single regional health system in the US. Additional studies are needed in unselected and genetically diverse populations to better define general population prevalence and phenotypic spectrum.

Family-Based Telehealth Initiative to Improve Nutrition and Physical Activity for Children With Obesity and Its Utility During COVID-19: A Mixed Methods Evaluation.

Guidelines recommend primary care providers refer children with obesity to behavioral interventions, but given limited program availability, access, and parental engagement, referrals remain rare. We developed telehealth coaching interventions for families whose children received care at a health system in Pennsylvania, United States in 2019-2020. Intervention referrals were facilitated by the pediatrician and/or project team for 6-12-year-old children with obesity following well-child visits. Participants chose one of three 26-week interventions focused on healthy eating, physical activity, or a hybrid clinical/nutrition intervention. Interventions engaged parents as change agents, enhancing self-efficacy to model and reinforce behavior and providing resources to help create a healthy home environment. We enrolled 77 of 183 eligible parent/child dyads. We used mixed methods to evaluate the interventions. Repeated measures models among participants showed significant reductions in obesogenic nutrition behaviors post-intervention and at 1-year follow-up, including a reduction in sugar-sweetened beverage intake of 2.14 servings/week (95% confidence interval: -3.45, -0.82). There were also improvements in obesoprotective nutrition behaviors (e.g., frequency of family meals, parental self-efficacy related to meal management). One year post-baseline, we observed no significant differences in changes in body mass index (BMI) z-scores comparing child participants with matched controls. Given potential impacts of COVID-19 community restrictions on study outcomes, we conducted qualitative interviews with 13 participants during restrictions, which exemplified how disrupted routines constrained children's healthy behaviors but that intervention participation prepared parents by providing cooking and physical activities at home. Findings support the potential of a telehealth-delivered nutrition intervention to support adoption of healthy weight behaviors.

Cancer in deceased adults with intellectual disabilities: English population-based study using linked data from three sources.

OBJECTIVE: To improve our understanding of cancer in adults with intellectual disabilities. DESIGN: Population-based study using linked data about deceased adults from the Learning (Intellectual) Disabilities Mortality Review (LeDeR) programme, the national cancer registry and NHS Digital. SETTING: England. PARTICIPANTS: 1096 adults with intellectual disabilities identified by the LeDeR programme who died between 1 January 2017 and 31 December 2019. OUTCOME MEASURE: Any form of cancer listed as a long-term health condition by a LeDeR reviewer or 10th edition of the International Classification of Diseases codes C00-D49 included on Parts I or II of the Medical Certificate of Cause of Death. RESULTS: In decedents with intellectual disabilities and cancer, more than a third (35%; n=162) had cancer diagnosed via emergency presentations. Almost half (45%; n=228) of cancers were at stage IV when diagnosed. More than a third (36%; n=309) of underlying causes of deaths were of cancers of the digestive system; almost half of these (48%; n=147) were cancer of the colon, rectum or anus. Of those who died with colorectal cancer, 43% were below the age threshold for colorectal screening. CONCLUSIONS: In decedents with intellectual disabilities, symptoms suggestive of cancer had tended to be identified most frequently as an emergency and at a late stage. There is a need for greater awareness of symptoms of cancer in this population, a lower threshold for referral by General Practitioners (GPs), accelerated access to diagnosis and treatment and consideration paid to lowering the age for colorectal screening.

Association of varicose veins with rare protein-truncating variants in PIEZO1 identified by exome sequencing of a large clinical population.

OBJECTIVE: The present study sought to determine whether protein-truncating variants (PTVs) in PIEZO1 and CASZ1 genes, previously shown to be associated with varicose veins, were associated with an altered risk of varicose veins. METHODS: An exome sequence database of 131,918 participants from the Geisinger MyCode Community Health Initiative was used to identify individuals with genetic variants in the PIEZO1 or CASZ1 gene. Clinical phenotypes, including varicose vein diagnoses, were determined by analysis of the electronic health record data. RESULTS: We identified 12,531 individuals (9.5%) with a diagnosis of varicose veins. Exome sequence data identified 92 PIEZO1 PTVs in 305 heterozygous carriers. PIEZO1 PTVs were significantly enriched in those with varicose vein (0.37% of cases vs 0.22% of controls; odds ratio [OR], 1.7; P = .0010). Nearly all varicose vein cases were associated with frameshift or stop-gain PTVs (OR, 3.0 for stop-gain [P = .0001]; OR, 2.9 for frameshift variants [P < .0001]). In the varicose vein cases, the PTV carriers were more likely to have an encounter with a vascular surgeon (62.5% for PTV carriers; 36.9% for noncarriers; P = .0003) and more likely to have received vein ablation therapy (OR, 6.9; P < .0001). No association was found between PIEZO1 PTVs and lymphedema, and no association was found for rare missense variants in PIEZO1 with varicose veins. PTVs in CASZ1 were extremely rare (16 total carriers), with none identified in those with varicose vein. CONCLUSIONS: Rare PTVs in PIEZO1 but not CASZ1 were associated with varicose veins and the need for vein ablation therapy. These results have demonstrated that PTVs in the PIEZO1 gene are rare but represent strong genetic risk factors for varicose veins and the need for vein ablation therapy. These results have also identified a potential biologic mechanism and target for the development of novel therapies.

Effects of sustained weight loss on outcomes associated with obesity comorbidities and healthcare resource utilization.

OBJECTIVE: Determine the impact of long-term non-surgical weight loss maintenance on clinical relevance for osteoarthritis, cancer, opioid use, and depression/anxiety and healthcare resource utilization. METHODS: A cohort of adults receiving primary care within Geisinger Health System between 2001-2017 was retrospectively studied. Patients with ≥3 weight measurements in the two-year index period and obesity at baseline (BMI ≥30 kg/m2) were categorized: Obesity Maintainers (reference group) maintained weight within +/-3%; Weight Loss Rebounders lost ≥5% body weight in year one, regaining ≥20% of weight loss in year two; Weight Loss Maintainers lost ≥5% body weight in year one, maintaining ≥80% of weight loss. Association with development of osteoarthritis, cancer, opioid use, and depression/anxiety, was assessed; healthcare resource utilization was quantified. Magnitude of weight loss among maintainers was evaluated for impact on health outcomes. RESULTS: In total, 63,567 patients were analyzed including 67% Obesity Maintainers, 19% Weight Loss Rebounders, and 14% Weight Loss Maintainers; median follow-up was 9.7 years. Time until osteoarthritis onset was delayed for Weight Loss Maintainers compared to Obesity Maintainers (Logrank test p <0.0001). Female Weight Loss Maintainers had a 19% and 24% lower risk of developing any cancer (p = 0.0022) or obesity-related cancer (p = 0.0021), respectively. No significant trends were observed for opioid use. Weight loss Rebounders and Maintainers had increased risk (14% and 25%) of future treatment for anxiety/depression (both <0.0001). Weight loss maintenance of >15% weight loss was associated with the greatest decrease in incident osteoarthritis. Healthcare resource utilization was significantly higher for Weight Loss Rebounders and Maintainers compared to Obesity Maintainers. Increased weight loss among Weight Loss Maintainers trended with lower overall healthcare resource utilization, except for hospitalizations. CONCLUSIONS: In people with obesity, sustained weight loss was associated with greater clinical benefits than regained short-term weight loss and obesity maintenance. Higher weight loss magnitudes were associated with delayed onset of osteoarthritis and led to decreased healthcare utilization.

Exhaustive Reduction of Esters Enabled by Nickel Catalysis.

We report a one-step procedure to directly reduce unactivated aryl esters into their corresponding tolyl derivatives. This is achieved by an organosilane-mediated ester hydrosilylation reaction and subsequent Ni/NHC-catalyzed hydrogenolysis. The resulting conditions provide a direct and efficient alternative to multi-step procedures for this transformation that often require the use of hazardous metal hydrides. Applications in the synthesis of -CD3-containing products, derivatization of bioactive molecules, and chemoselective reduction in the presence of other C-O bonds are demonstrated.

Identification of the Clinical Development Candidate MRTX849, a Covalent KRASG12C Inhibitor for the Treatment of Cancer.

Capping off an era marred by drug development failures and punctuated by waning interest and presumed intractability toward direct targeting of KRAS, new technologies and strategies are aiding in the target's resurgence. As previously reported, the tetrahydropyridopyrimidines were identified as irreversible covalent inhibitors of KRASG12C that bind in the switch-II pocket of KRAS and make a covalent bond to cysteine 12. Using structure-based drug design in conjunction with a focused in vitro absorption, distribution, metabolism and excretion screening approach, analogues were synthesized to increase the potency and reduce metabolic liabilities of this series. The discovery of the clinical development candidate MRTX849 as a potent, selective covalent inhibitor of KRASG12C is described.

Partial loss of actin nucleator actin-related protein 2/3 activity triggers blebbing in primary T lymphocytes.

T lymphocytes utilize amoeboid migration to navigate effectively within complex microenvironments. The precise rearrangement of the actin cytoskeleton required for cellular forward propulsion is mediated by actin regulators, including the actin-related protein 2/3 (Arp2/3) complex, a macromolecular machine that nucleates branched actin filaments at the leading edge. The consequences of modulating Arp2/3 activity on the biophysical properties of the actomyosin cortex and downstream T cell function are incompletely understood. We report that even a moderate decrease of Arp3 levels in T cells profoundly affects actin cortex integrity. Reduction in total F-actin content leads to reduced cortical tension and disrupted lamellipodia formation. Instead, in Arp3-knockdown cells, the motility mode is dominated by blebbing migration characterized by transient, balloon-like protrusions at the leading edge. Although this migration mode seems to be compatible with interstitial migration in three-dimensional environments, diminished locomotion kinetics and impaired cytotoxicity interfere with optimal T cell function. These findings define the importance of finely tuned, Arp2/3-dependent mechanophysical membrane integrity in cytotoxic effector T lymphocyte activities.

Systematic characterization of germline variants from the DiscovEHR study endometrial carcinoma population.

BACKGROUND: Endometrial cancer (EMCA) is the fifth most common cancer among women in the world. Identification of potentially pathogenic germline variants from individuals with EMCA will help characterize genetic features that underlie the disease and potentially predispose individuals to its pathogenesis. METHODS: The Geisinger Health System's (GHS) DiscovEHR cohort includes exome sequencing on over 50,000 consenting patients, 297 of whom have evidence of an EMCA diagnosis in their electronic health record. Here, rare variants were annotated as potentially pathogenic. RESULTS: Eight genes were identified as having increased burden in the EMCA cohort relative to the non-cancer control cohort. None of the eight genes had an increased burden in the other hormone related cancer cohort from GHS, suggesting they can help characterize the underlying genetic variation that gives rise to EMCA. Comparing GHS to the cancer genome atlas (TCGA) EMCA germline data illustrated 34 genes with potentially pathogenic variation and eight unique potentially pathogenic variants that were present in both studies. Thus, similar germline variation among genes can be observed in unique EMCA cohorts and could help prioritize genes to investigate for future work. CONCLUSION: In summary, this systematic characterization of potentially pathogenic germline variants describes the genetic underpinnings of EMCA through the use of data from a single hospital system.

Immune regeneration in irradiated mice is not impaired by the absence of DPP9 enzymatic activity.

The ubiquitous intracellular protease dipeptidyl peptidase 9 (DPP9) has roles in antigen presentation and B cell signaling. To investigate the importance of DPP9 in immune regeneration, primary and secondary chimeric mice were created in irradiated recipients using fetal liver cells and adult bone marrow cells, respectively, using wild-type (WT) and DPP9 gene-knockin (DPP9S729A) enzyme-inactive mice. Immune cell reconstitution was assessed at 6 and 16 weeks post-transplant. Primary chimeric mice successfully regenerated neutrophils, natural killer, T and B cells, irrespective of donor cell genotype. There were no significant differences in total myeloid cell or neutrophil numbers between DPP9-WT and DPP9S729A-reconstituted mice. In secondary chimeric mice, cells of DPP9S729A-origin cells displayed enhanced engraftment compared to WT. However, we observed no differences in myeloid or lymphoid lineage reconstitution between WT and DPP9S729A donors, indicating that hematopoietic stem cell (HSC) engraftment and self-renewal is not diminished by the absence of DPP9 enzymatic activity. This is the first report on transplantation of bone marrow cells that lack DPP9 enzymatic activity.

Correction to: Systematic characterization of germline variants from the DiscovEHR study endometrial carcinoma population.

Following publication of the original article [1], the authors reported that Fig. 1 was not correctly processed during the production process. The correct Fig. 1 is given below.

DiaRem2: Incorporating duration of diabetes to improve prediction of diabetes remission after metabolic surgery.

BACKGROUND: DiaRem is a validated tool for predicting the likelihood of type 2 diabetes (T2D) remission after Roux-en-Y gastric bypass (RYGB) surgery. OBJECTIVES: The objective of this study was to determine if the addition of duration of T2D to DiaRem improves its ability to discriminate between patients with or without T2D remission and/or to reclassify presurgery patients into accurate risk groups. SETTING: Academic Medical Center. METHODS: This study included patients consented into a prospective registry of Roux-en-Y gastric bypass between July 2009 and November 2015 with known duration of T2D (n = 307). Electronic health record-derived duration of T2D was compared with patient reported duration of T2D in a subset of patients (n = 48). DiaRem2 was created using clinical variables from DiaRem and duration of T2D. Area under the curve and the net reclassification index were used to assess increased performance of DiaRem2. RESULTS: Self-reported duration of T2D was highly concordant with electronic health record-derived T2D duration (96% agreement). Early T2D remission occurred in 44% of patients. DiaRem2 included age, hemoglobin A1C, insulin medication use, and duration of T2D. DiaRem2 had a higher area under the curve than DiaRem (.876 versus .850, P = .026), reduced the number of remission risk groups from 5 down to 3, and reclassified patients from intermediate to either high or low remission groups (net reclassification index, P < .0001). CONCLUSIONS: DiaRem2 simplifies and improves the accuracy of assessing probability of T2M remission after Roux-en-Y gastric bypass. Self-reported duration of T2D is an acceptable surrogate for T2D duration derived from clinical data.

Clinical Characteristics of Roux-en-Y Gastric Bypass Patients with Death from Accidental Overdose or Intentional Self-Harm: a Descriptive Study.

PURPOSE: The objective of this descriptive study was to identify clinical characteristics of Roux-en-Y gastric bypass (RYGB) patients who died from intentional self-harm or accidental overdose postoperatively. MATERIALS AND METHODS: This retrospective, descriptive study included RYGB patients from a large rural medical center that completed surgery between January 2004 and December 2014 and died from intentional self-harm or accidental overdose through December 2015. Specific causes of death were obtained from the National Death Index and clinical data from electronic health records. Clinical characteristics explored were age, sex, time to surgery, weight loss expectations, postoperative weight loss, medication, diagnoses, psychiatric histories (diagnoses, self-harm, suicidal ideation and behaviors, medications, substance use, preoperative Beck Depression Inventory-II scores), pain, social support, and reported life stressors. RESULTS: Overall, 22 patients of 146 total deceased patients died from intention self-harm (n = 6) or accidental overdose (n = 16) over the study period (77.3% female, mean age at time of surgery = 38.4 ± 9.1 years). Younger age (< 40 years), history of self-harm or depression, preoperative pain, and use of opioids at the time of surgery emerged as common characteristics in weight loss surgery patients who died from intentional self-harm or accidental overdose. No trends regarding social support, life stressors, or actual or expected weight loss were identified. CONCLUSION: Certain weight loss surgery patients may be at risk for death from self-harm or overdose and may benefit from greater surveillance postoperatively.

All-Cause and Specific-Cause Mortality Risk After Roux-en-Y Gastric Bypass in Patients With and Without Diabetes.

OBJECTIVE: This study assessed all-cause and specific-cause mortality after Roux-en-Y gastric bypass (RYGB) and in matched control subjects, stratified by diabetes status. RESEARCH DESIGN AND METHODS: RYGB patients were matched by age, BMI, sex, and diabetes status at time of surgery to nonsurgical control subjects using data from the electronic health record. Kaplan-Meier curves and Cox regression were used to assess differences in all-cause and specific-cause mortality between RYGB patients and control subjects with and without diabetes. RESULTS: Of the 3,242 eligible RYGB patients enrolled from January 2004 to December 2015, control subjects were identified for 2,428 (n = 625 with diabetes and n = 1,803 without diabetes). Median postoperative follow-up was 5.8 years for patients with diabetes and 6.7 years for patients without diabetes. All-cause mortality was reduced in RYGB patients compared with control subjects only for those with diabetes at the time of surgery (adjusted hazard ratio 0.44; P < 0.0001). Mortality was not significantly improved in RYGB patients without diabetes compared with control subjects without diabetes (adjusted hazard ratio 0.84; P = 0.37). Deaths from cardiovascular diseases (P = 0.011), respiratory conditions (P = 0.017), and diabetes P = 0.011) were more frequent in control subjects with diabetes than in RYGB patients with diabetes. RYGB patients without diabetes were less likely to die of cancer (P = 0.0038) and respiratory diseases (P = 0.046) than control subjects without diabetes but were at higher risk of death from external causes (P = 0.012), including intentional self-harm (P = 0.025), than control subjects without diabetes. CONCLUSIONS: All-cause mortality benefits of RYGB are driven predominantly by patients with diabetes at the time of surgery. RYGB patients with diabetes were less likely to die of cardiovascular diseases, diabetes, and respiratory conditions than their counterparts without RYGB.

Beryllium nitrate inhibits fibroblast migration to disrupt epimorphic regeneration.

Epimorphic regeneration proceeds with or without formation of a blastema, as observed for the limb and skin, respectively. Inhibition of epimorphic regeneration provides a means to interrogate the cellular and molecular mechanisms that regulate it. In this study, we show that exposing amputated limbs to beryllium nitrate disrupts blastema formation and causes severe patterning defects in limb regeneration. In contrast, exposing full-thickness skin wounds to beryllium only causes a delay in skin regeneration. By transplanting full-thickness skin from ubiquitous GFP-expressing axolotls to wild-type hosts, we demonstrate that beryllium inhibits fibroblast migration during limb and skin regeneration in vivo Moreover, we show that beryllium also inhibits cell migration in vitro using axolotl and human fibroblasts. Interestingly, beryllium did not act as an immunostimulatory agent as it does in Anurans and mammals, nor did it affect keratinocyte migration, proliferation or re-epithelialization, suggesting that the effect of beryllium is cell type-specific. While we did not detect an increase in cell death during regeneration in response to beryllium, it did disrupt cell proliferation in mesenchymal cells. Taken together, our data show that normal blastema organogenesis cannot occur without timely infiltration of local fibroblasts and highlights the importance of positional information to instruct pattern formation during regeneration. In contrast, non-blastemal-based skin regeneration can occur despite early inhibition of fibroblast migration and cell proliferation.

Bariatric Surgery Patients and Their Families: Health, Physical Activity, and Social Support.

BACKGROUND: This study evaluated the social environment of bariatric surgery patients in the preoperative period. METHODS: Forty bariatric surgery patients (mean = 46.2 ± 11.2 years), 35 adult cohabitating family members (mean = 45.2 ± 12.7 years), and 15 cohabitating children (mean = 11.5 ± 3.6 years) were recruited from a large rural medical center. Adult participants (patients and family members) completed height, weight, body composition, blood draws, and physical activity assessments (accelerometry), as well as eating behavior and social support inventories before the patient underwent bariatric surgery. Child participants completed demographic, height, and weight assessment only. RESULTS: Over 90 % of adult family members were overweight or obese (body mass index (BMI) ≥ 25 kg/m2, as were 50 % of children (BMI percentile ≥ 85 %). More than one third (37.1 %) of family members met the criteria for moderate to severe insulin resistance. Physical activity measured by accelerometry was moderately correlated between the patient and adult family members (r = 0.46, p = 0.023). Bariatric surgery patients reported high levels of social support from their family members on multiple social support measures. CONCLUSIONS: Many family members of bariatric surgery patients also lived with obesity and related comorbidities, and demonstrate high sedentary behavior. However, patients reported high levels of support from family members, including support in following a healthy diet and engaging in physical activity. Engaging families in behavior change may help bariatric surgery patients and their families to become healthier.

Apolipoprotein A-I Limits the Negative Effect of Tumor Necrosis Factor on Lymphangiogenesis.

OBJECTIVE: Lymphatic endothelial dysfunction underlies the pathogenesis of many chronic inflammatory disorders. The proinflammatory cytokine tumor necrosis factor (TNF) is known for its role in disrupting the function of the lymphatic vasculature. This study investigates the ability of apolipoprotein (apo) A-I, the principal apolipoprotein of high-density lipoproteins, to preserve the normal function of lymphatic endothelial cells treated with TNF. APPROACH AND RESULTS: TNF decreased the ability of lymphatic endothelial cells to form tube-like structures. Preincubation of lymphatic endothelial cells with apoA-I attenuated the TNF-mediated inhibition of tube formation in a concentration-dependent manner. In addition, apoA-I reversed the TNF-mediated suppression of lymphatic endothelial cell migration and lymphatic outgrowth in thoracic duct rings. ApoA-I also abrogated the negative effect of TNF on lymphatic neovascularization in an ATP-binding cassette transporter A1-dependent manner. At the molecular level, this involved downregulation of TNF receptor-1 and the conservation of prospero-related homeobox gene-1 expression, a master regulator of lymphangiogenesis. ApoA-I also re-established the normal phenotype of the lymphatic network in the diaphragms of human TNF transgenic mice. CONCLUSIONS: ApoA-I restores the neovascularization capacity of the lymphatic system during TNF-mediated inflammation. This study provides a proof-of-concept that high-density lipoprotein-based therapeutic strategies may attenuate chronic inflammation via its action on lymphatic vasculature.