Evidence For Mechanism Research Articles

IMPACT OF REAL-LIFE ENVIRONMENTAL EXPOSURES ON REPRODUCTION: Evidence for reproductive health effects following exposure to hydraulic fracturing chemical mixtures.

Unconventional oil and natural gas (UOG) operations, particularly hydraulic fracturing, have revolutionized oil and gas production, using and containing complex mixtures of chemicals that may impact reproductive health. While there is growing evidence for effects on births in hydraulic fracturing/UOG regions and good mechanistic evidence for potential reproductive toxicity, there is much research still needed to make firm conclusions about these practices and reproductive health. Unconventional oil and natural gas (UOG) operations have emerged over the last four decades to transform oil and gas production in the United States and globally by unlocking previously inaccessible hydrocarbon deposits. UOG development utilizes many compounds associated with conventional oil and gas, as well as some specific to UOG extraction, particularly during hydraulic fracturing (HF). While research is increasing on UOG chemicals and their mixtures, this review discusses the current evidence for reproductive toxicity following exposures to UOG/HF mixtures. These complex chemical mixtures have been demonstrated to interact with numerous mechanisms known to influence reproductive health. A growing number of environmental and controlled laboratory testing studies have reported adverse reproductive health effects in animals exposed to various UOG chemical mixtures. An expanding body of epidemiological literature has assessed adverse birth outcomes, although none has directly examined reproductive measures such as time to pregnancy, semen quality, and other direct measures of fertility. The existing literature provides moderate evidence for decreased birth weights, increased risk of small for gestational age and/or preterm birth, increased congenital abnormalities, and increased infant mortality, though importantly, studies are widely variable in methods used. Most studies utilized distance from UOG operations as an exposure proxy and did not measure actual chemical exposures experienced by those living near these operations. As such, while there is growing evidence for effects on births in these regions and good mechanistic evidence for potential reproductive toxicity, there is much research still needed to make firm conclusions about UOG development and reproductive health.

Nuclear localization of Arabidopsis HD-Zip IV transcription factor GLABRA2 is driven by importin α.

GLABRA2 (GL2), a class IV homeodomain leucine-zipper (HD-Zip IV) transcription factor from Arabidopsis, is a developmental regulator of specialized cell types in the epidermis. GL2 contains a monopartite nuclear localization sequence (NLS) that is conserved in most HD-Zip IV members across the plants. We demonstrate that NLS mutations affect nuclear transport and result in a loss-of-function phenotypes. NLS fusions to enhanced yellow fluorescent protein (EYFP) show that it is sufficient for nuclear localization in roots and trichomes. Despite partial overlap of the NLS with the homeodomain, genetic dissection indicates that nuclear localization and DNA binding are separable functions. Affinity purification of GL2 from plants followed by MS-based proteomics identified importin α (IMPα) isoforms as potential GL2 interactors. NLS structural prediction and molecular docking studies with IMPα-3 revealed major interacting residues. Cytosolic yeast two-hybrid assays and co-immunoprecipitation experiments with recombinant proteins verified NLS-dependent interactions between GL2 and several IMPα isoforms. IMPα triple mutants (impα-1,2,3) exhibit abnormal trichome formation and defects in GL2 nuclear localization in trichomes, consistent with tissue-specific and redundant functions of IMPα isoforms. Taken together, our findings provide mechanistic evidence for IMPα-dependent nuclear localization of GL2 in Arabidopsis, a process that is critical for cell type differentiation of the epidermis.

The Association between Cadmium Exposure and Thyroid Function in Animals: A Systematic Review.

Several studies have indicated an association between cadmium (Cd) exposure and the induction of thyroid dysfunction in animal models. Objective and Aims: There are inconsistent findings on the effect of Cd on the thyroid gland. Therefore, this systematic study was designed to determine the association between changes in thyroid function markers and Cd exposure in animals. The search was performed on Scopus, PubMed, Web of Science and databases, and Google Scholar until May 2023. Studies on the relationship between Cd exposure and fish's thyroid function were conducted on rodents and fish. In total, 171 articles were obtained from the main databases using the search strategy mentioned in this study. Finally, 24 articles were selected according to our inclusion criteria for systematic studies. The findings indicated an increase/decrease or no change in triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) levels in rodents, fish, and animals exposed to Cd. Our findings indicated an association between Cd exposure and thyroid dysfunction in rodents, fish, and other animals. However, the association between urinary and blood Cd levels and thyroid function remains unclear in humans because of controversial findings and a lack of strong mechanistic evidence. We perform large cohort human studies to the answer to this question.

Ischemic preconditioning: what else can it do…?

Ischemic preconditioning (IPC) can enhance maximal strength likely due to neural priming. Cruz et al. (Cruz R, Tramontin AF, Oliveira AS, Caputo F, Denadai BS, Greco CC. Scand J Med Sci Sports 34: e14591, 2024) examined the neurophysiological mechanisms responsible for the ergogenic effect. Although key neurophysiological measures remained largely unchanged, voluntary activation and maximal strength were greater following IPC than sham-IPC. Although the mechanistic evidence remains inconclusive, the greater maximal strength provides further evidence of the ergogenic benefit of IPC. Researchers should continue examining the broader functional implications of IPC.

Photochemical Initiation and Reactions of Thiyl Radicals Studied with SH2' Radical Traps.

A radical trapping method based on an SH2' homolytic substitution reaction was applied to study the mechanism of a photochemical spirocyclisation of indole-ynones in the presence of thiols. Starting material, products and a range of trapped radical intermediates were simultaneously detected in reaction mixtures by mass spectrometry (MS). The trapped intermediates included both initiating and main chain propagating radicals. These data made it possible to propose a self-initiation mechanism consistent with the originally postulated photoexcitation of an intramolecular electron donor-acceptor complex of the substrate. The effect of thiol structure on the MS peak intensity of the reaction components was rationalised in terms of the relative stability of the radical intermediates. The results were compared to a simpler related reaction, a photochemical thiol-ene addition where reagents, products and trapped intermediate radicals were also detected by MS. Relative MS peak intensities were again explained by a combination of electronic and steric effects on the stability of intermediate radicals. Overall, SH2' radical trapping was demonstrated to be a powerful experimental technique for providing mechanistic evidence on photochemical and other organic radical reactions.

Methynissolin confers protection against gastric carcinoma via targeting RIPK2

Gastric carcinoma (GC) is one of the most common malignant tumors worldwide, and ranks fifth in incidence and top 5 in tumor-associated mortality. Unfortunately, the molecular mechanisms contributing to GC development are still unclear, urgently requiring more studies. It has been proposed that the multifunctional regulator receptor-interacting protein 2 (RIPK2) is both a regulator that induces stomach cancer and its complications such as cachexia. However, the potential molecular function of RIPK2 on regulation of GC is largely unknown. Moreover, 3,9-di-O-methylnissolin, a flavonoid derived from the roots of Astragalus membranaceus, exhibits protective effects against cancer, inflammation, and bacterial infections. Unfortunately the antineoplastic mechanism of oral exposure of such flavonoid are poorly understood. It remains unknown whether 3,9-di-O-methylnissolin is capable of mitigating GC progression, and potential molecular mechanism. This study aims to provide mechanistic evidence that the 3,9-di-O-methylnissolin-triggered mitigation of GC by repressing RIPK2 activity and its downstream ASK1 signaling. The TCGA database, GEO database, subjects with GC phenotype and GC cell lines were used in this work. 3,9-di-O-methylnissolin intervention reduces stomach cancer cell migration, proliferation and invasion in vitro. Also, 3,9-di-O-methylnissolin confers protection against tumor growth in xenograft model in vivo. Mechanistically, on the other hand, in the para-carcinoma tissue, overexpression of RIPK2 reduces lipogenesis and disturbs lipid homeostasis. Overexpression of RIPK2 activates downstream signaling of ASK1, which in turn downregulates PPARα, a master regulator of lipid metabolism. This process results in lower lipogenesis and downregulation of a set of PPARα target genes. Astragalus membranaceus naturally produces 3,9-di-O-methylnissolin, a bioactive substance that when suppression of ASK1 by methylnissolin reduces RIPK2-induced GC and its related cachexia and restores lipid homeostasis. These findings offer important new understandings of stomach cancer and could aid in the development of treatment plans for gastric carcinoma and cachexia related to cancer.

Defining Retinal Vasculitis

PurposeTo assess the validity of retinal vasculitis as the preferred diagnostic term for multiple conditions. DesignPerspective MethodsExpert opinion and review of literature focused on the current nosology and pathology of retinal vasculitis. Interpretation of the subset of intraocular inflammation named retinal vasculitis based on fundamental knowledge of the blood-retinal barrier, the neurovascular unit and pathological and functional responses to a variety of stimuli. Correlation with multimodal imaging and known mechanisms of immunologically mediated disease. ResultsA search of Medline in early 2024 for the phrase “retinal vasculitis” resulted in 2041 citations encompassing immunologic, genetic, neoplastic, infectious, drug- and ischemia-related disorders. Classification schemes and angiographic grading systems are descriptive and do not address pathologic mechanisms adequately, in part due to lack of histologic confirmation. Although OCT angiography holds promise for better imaging of retinal vascular changes, it does not reveal the key feature of leakage and only partially improves understanding of pathophysiology. Diagnosing catastrophic retinal vascular occlusion after intravitreal injections as a retinal vasculitis is the most recent example of speculative application of the term to complex and rare disorders. ConclusionsRetinal vasculitis is a diagnostic term that is over-used and imprecise. Revised nosology should limit the term to primary inflammation of the retinal vasculature itself that results in opening of the blood-retinal barrier with or without retinal vascular occlusions. Pending new histologic or mechanistic evidence, the provisional term of retinal vascular inflammation or retinal vasculopathy should be used for leakage or occlusion occurring in the context of intraocular inflammation.

Mutual effects of gestational diabetes and schizophrenia: how can one promote the other?: A review.

Although the physical complications of gestational diabetes mellitus (GDM) are well known, emerging evidence suggests a significant link with psychiatric conditions such as schizophrenia (SCZ). This review aimed to explore the extent, nature, and implications of the association between GDM and SCZ, exploring how the 2 conditions may reciprocally influence each other. We conducted a comprehensive literature review and, analyzed clinical and mechanistic evidence supporting the mutual effects of GDM and SCZ. This review examined factors such as neurodevelopment and the impact of antipsychotics. The study found that Maternal GDM increases the risk of SCZ in offspring. Conversely, women with SCZ were more prone to hyperglycemic pregnancies. The research highlights significant regional variations in GDM prevalence, with the highest rate in the Middle East, North Africa, and South-East Asia regions. These regional variations may have an impact on the epidemiology of SCZ. Furthermore, this review identifies the potential biological and environmental mechanisms underlying these associations. There is a bidirectional relationship between GDM and SCZ, with each disorder potentially exacerbating the others. This relationship has significant implications for maternal and offspring health, particularly in regions with high GDM prevalence. These findings underline the need for integrated care approaches for women with SCZ during pregnancy and the importance of monitoring and managing GDM to mitigate the risk of SCZ in the offspring. Notably, this study recognizes the need for further research to fully understand these complex interactions and their implications for healthcare.

The Drug-Drug Interaction between Erlotinib and OSI-930 Is Mediated through Aldehyde Oxidase Inhibition.

The propensity for aldehyde oxidase (AO) substrates to be implicated in drug-drug interactions (DDIs) is not well understood due to the dearth of potent inhibitors that elicit in vivo inhibition of AO. Although there is only one reported instance of DDI that has been ascribed to the inhibition of AO to date, the supporting evidence for this clinical interaction is rather tenuous, and its veracity has been called into question. Our group recently reported that the epidermal growth factor receptor inhibitor erlotinib engendered potent time-dependent inhibition of AO with inactivation kinetic constants in the same order of magnitude as its free circulating plasma concentrations. At the same time, it was previously reported that the concomitant administration of erlotinib with the investigational drug OSI-930 culminated in a an approximately twofold increase in its systemic exposure. Although the basis underpinning this interaction remains unclear, the structure of OSI-930 contains a quinoline motif that is amenable to oxidation at the electrophilic carbon adjacent to the nitrogen atom by molybdenum-containing hydroxylases like AO. In this study, we conducted metabolite identification that revealed that OSI-930 undergoes AO metabolism to a mono-oxygenated 2-oxo metabolite and assessed its formation kinetics in human liver cytosol. Additionally, reaction phenotyping in human hepatocytes revealed that AO contributes nearly 50% to the overall metabolism of OSI-930. Finally, modeling the interaction between erlotinib and OSI-930 using a mechanistic static model projected an ∼1.85-fold increase in the systemic exposure of OSI-930, which accurately recapitulated clinical observations. SIGNIFICANCE STATEMENT: This study delineates an aldehyde oxidase (AO) metabolic pathway in the investigational drug OSI-930 for the first time and confirmed that it represented a major route of metabolism through reaction phenotyping in human hepatocytes. Our study provided compelling mechanistic and modeling evidence for the first instance of an AO-mediated clinical drug-drug interaction stemming from the in vivo inhibition of the AO-mediated quinoline 2-oxidation pathway in OSI-930 by erlotinib.

HSD22 Extending External Validity of Rcts and Meta-Analysis through Transportability Analysis and Integration of Mechanistic Research Evidence

HSD22 Extending External Validity of Rcts and Meta-Analysis through Transportability Analysis and Integration of Mechanistic Research Evidence

Human milk affects TLR4 activation and LPS-induced inflammatory cytokine expression in Caco-2 intestinal epithelial cells

Human milk (HM) components affect immune cell toll-like receptor 4 (TLR4) signaling. However, studies examining the immunomodulatory impacts of HM on TLR4 signaling in intestinal epithelial cells (IECs) are limited. This study utilized both a TLR4 reporter cell line and a Caco-2 IEC model to examine the effects of HM on lipopolysaccharide (LPS)-induced TLR4 activation and cytokine responses, respectively. Additionally, we performed fast protein liquid chromatography and mass spectrometry to identify a HM component that contributes to the effect of HM on LPS/TLR4 signaling. HM enhances LPS-induced TLR4 signaling as well as LPS-induced IEC gene expression of pro-inflammatory cytokines and negative regulators of NF-κB. Human serum albumin (HSA) present in HM contributes to these effects. HSA within HM synergizes with LPS to induce IEC gene expression of pro-inflammatory cytokines and negative regulators of NF-κB. Altogether, this study provides mechanistic evidence behind the immunomodulatory function of HM on IECs, which may contribute to an enhanced immune response in breast-fed neonates.

Abstract B013: Deep learning-based prediction of synthetic essentialities in CTNNB1-mutated hepatocellular carcinoma

Abstract Background: Synthetic essentiality represents a promising therapeutic approach by identifying genes that are necessary for the proliferation and survival of tumors harboring hard-to-target gene alterations. Understanding and accurately predicting synthetic essential genes, through genetic dependencies, may reveal therapeutically effective drug targets in a specific molecular context. Deep learning, as exemplified by our published DeepDEP model, has the potential to capture intricate multi-omic profiles for such prediction tasks. However, the validity of such tools in specific biological contexts remains to be fully examined and presents a major obstacle to adoption by researchers. Materials and Methods: To address this gap, we conducted a case study in which we screened for synthetic essential genes for one of the most frequently mutated and yet undruggable genes, CTNNB1, in hepatocellular carcinoma (HCC). Specifically, we predicted the genetic dependencies of each HCC patient in The Cancer Genome Atlas (TCGA; n=346) by DeepDEP and identified potential dependencies that were intensified with the presence of CTNNB1 mutations. The top 10 genes, ranked by p-value of differential gene-effect scores for CTNNB1-mutated (n=92) versus CTNNB1-WT HCC (n=254), were reviewed in the literature to validate their essentiality in CTNNB1-mutated HCC as well as their potential for pharmacologic inhibition. Survival analysis was performed using published data from the IMBrave150 trial to validate one of the findings. Results: Experimental evidence in the literature supported the essentiality of many of the top 10 predicted genes for CTNNB1-mutated HCC, including one gene with mechanistic evidence of being a transcriptional co-activator of β-catenin target genes. Furthermore, several of these genes have known pharmacologic inhibitors which are either natural compounds or FDA-approved drugs. One example was PDGFB, which encodes a ligand activating the PDGF signaling pathway. PDGF signaling is targeted by sorafenib, an FDA-approved first line drug for HCC. Survival analysis of the sorafenib-treated arm of the IMBrave150 trial showed that patients with mutated CTNNB1 had improved progression-free survival compared to those with wild-type CTNNB1 (p = 0.044). Conclusions: Our study illustrates a potential application of deep learning to identify synthetic essential genes, including genes with readily available pharmacologic inhibitors, for targeting challenging gene alterations. Remarkably, our tool demonstrates the ability to predict cancer dependencies with molecular subtype specificity, suggesting a potential for in silico screening of gene dependencies to facilitate drug discovery and personalized medicine approaches. Our current efforts are focused on optimizing this computational pipeline and making it publicly available for cancer researchers. Citation Format: Tyler M. Yasaka, Michael Kasper, Li-Ju Wang, Michael Ning, Yufei Huang, Satdarshan P Monga, Yu-Chiao Chiu. Deep learning-based prediction of synthetic essentialities in CTNNB1-mutated hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr B013.

Uric acid in atherosclerosis and cardiovascular diseases: innocent bystander or ruthless killer?

Medical attention to uric acid (UA) has been increasing in recent years, mainly because this molecule has been shown to be associated with increased cardiovascular risk, both in the general population and in the hypertensive patients. A growing body of clinical and experimental data supports this view and prompts reconsideration of the role of UA in the development of atherosclerosis and the genesis of cardiovascular disease. It is known that this substance, in certain plasma concentrations, induces increased oxidative stress, a chronic inflammatory state, and a whole series of other modifications that are potentially deleterious at the cardiovascular level leading to hypertension, atherosclerosis, atrial fibrillation (AF), and other metabolic changes such as diabetes, metabolic syndrome, non-alcoholic fatty liver disease and kidney failure. Despite this epidemiologic and mechanistic evidence, the current guidelines from international cardiology scientific societies do not give precise indications in this regard, and some of them only suggest UA evaluation as part of an initial screening of the hypertensive patient. The purpose of this review is to briefly describe the main clinical and epidemiological evidence supporting the role of hyperuricemia as a possible emerging cardiovascular risk factor and to analyze the potential pathophysiological mechanisms through which elevated UA levels may exert a detrimental effect on the cardiovascular system.

Early opioid exposure (EOE) and impaired efficacy in patients with advanced NSCLC treated with PD-L1 inhibition: A pooled post hoc analysis of the POPLAR and OAK trials.

2607 Background: Mechanistic evidence suggests opioid signaling to modulate anti-tumor immunity. Whether opioids exposure may affect outcome of patients (pts) treated with immune checkpoint inhibitors is unproven, with clinical evidence being flawed by the negative associative bias between pain and higher burden of disease. Methods: We conducted a post-hoc analysis of the phase 3 OAK (NCT02008227) and phase 2 POPLAR (NCT01903993) trials, which randomized (1:1) pts with advanced NSCLC to receive either atezolizumab or docetaxel. We assessed the differential impact of early opioids exposure (EOE), defined as a minimum of 7 days exposure to any systemic opioids in the time window ranging between -30 to +30 from treatment initiation on efficacy from immunotherapy vs chemotherapy. Pts with ≤30 days survival follow-up were excluded to avoid immortal time bias. Results: After the exclusion of 60 pts, 718 and 686 pts treated with atezolizumab and docetaxel were included, with 341 (47.5%) and 308 (44.9%) pts with EOE respectively (p=0.32) and a median follow-up of 25.5 months (95% CI: 22.8-25.9). Baseline characteristics was balanced across cohorts. In the pooled population, EOE was significantly associated with poorer ECOG-PS (p<0.01) and burden of disease (p<0.01). Univariable analysis showed EOE to be significantly associated with decreased objective response rate (ORR, 11.7% vs 19.8%, p<0.01) and progression free survival (PFS, 1.9 vs 4.2 months, p<0.01) in the atezolizumab cohort, whereas no effect on ORR (17.7% vs 14.4%, p=0.25) and a less pronounced effect on PFS (3.5 vs 4.1 months, p=0.02) was reported for the docetaxel cohort. The pooled multivariable backward stepwise Cox regression used to select variables for validating the results individuated ECOG-PS, histology, tumor burden and race. In multivariable models EOE was associated with decreased ORR (OR 0.58, 95%CI: 0.37-0.92), increased risk of progression (HR 1.47, 95%CI: 1.26-1.72) and death (HR 1.70, 95%CI: 1.42-2.03) in the atezolizumab cohort while no negative impact on ORR/PFS was confirmed among the docetaxel cohort, with a less strong effect on OS (HR 1.44, 95%CI: 1.21-1.72). Multivariable interaction tests confirmed the differential impact of EOE on ORR (p<0.01) and PFS (p<0.01) between treatment modalities (immunotherapy vs chemotherapy). The results were additionally confirmed using IPTW models including all the baseline variables with an optimal distribution (SMD <0.05). Conclusions: EOE is associated with worse response/PFS from immunotherapy but not from chemotherapy exposure, suggesting a possible immune-modulating effect of opioids signaling on anti-tumor immunity. Considering that systemic opioids are the cornerstone of pain management in oncology further research for mitigation strategies, such as the potential use of PAMORAs, is needed. Clinical trial information: NCT02008227 and NCT01903993 .

Mechanistic Insights into the Function of 14-3-3 Proteins as Negative Regulators of Brassinosteroid Signaling in Arabidopsis.

Brassinosteroids (BRs) are vital plant steroid hormones sensed at the cell surface by a membrane signaling complex comprising the receptor kinase BRI1 and a SERK family co-receptor kinase. Activation of this complex lead to dissociation of the inhibitor protein BKI1 from the receptor and to differential phosphorylation of BZR1/BES1 transcription factors by the glycogen synthase kinase 3 protein BIN2. Many phosphoproteins of the BR signaling pathway, including BRI1, SERKs, BKI1 and BZR1/BES1 can associate with 14-3-3 proteins. In this study, we use quantitative ligand binding assays to define the minimal 14-3-3 binding sites in the N-terminal lobe of the BRI1 kinase domain, in BKI1, and in BZR1 from Arabidopsis thaliana. All three motifs require to be phosphorylated to specifically bind 14-3-3s with mid- to low-micromolar affinity. BR signaling components display minimal isoform preference within the 14-3-3 non-ε subgroup. 14-3-3λ and 14-3-3 ω isoform complex crystal structures reveal that BKI1 and BZR1 bind as canonical type II 14-3-3 linear motifs. Disruption of key amino acids in the phosphopeptide binding site through mutation impairs the interaction of 14-3-3λ with all three linear motifs. Notably, quadruple loss-of-function mutants from the non-ε group exhibit gain-of-function BR signaling phenotypes, suggesting a role for 14-3-3 proteins as overall negative regulators of the BR pathway. Collectively, our work provides further mechanistic and genetic evidence for the regulatory role of 14-3-3 proteins at various stages of the BR signaling cascade.

Polyphenol Compound 18a Modulates UCP1-Dependent Thermogenesis to Counteract Obesity.

Recent studies increasingly suggest that targeting brown/beige adipose tissues to enhance energy expenditure offers a novel therapeutic approach for treating metabolic diseases. Brown/beige adipocytes exhibit elevated expression of uncoupling protein 1 (UCP1), which is a thermogenic protein that efficiently converts energy into heat, particularly in response to cold stimulation. Polyphenols possess potential anti-obesity properties, but their pharmacological effects are limited by their bioavailability and distribution within tissue. This study discovered 18a, a polyphenol compound with a favorable distribution within adipose tissues, which transcriptionally activates UCP1, thereby promoting thermogenesis and enhancing mitochondrial respiration in brown adipocytes. Furthermore, in vivo studies demonstrated that 18a prevents high-fat-diet-induced weight gain and improves insulin sensitivity. Our research provides strong mechanistic evidence that UCP1 is a complex mediator of 18a-induced thermogenesis, which is a critical process in obesity mitigation. Brown adipose thermogenesis is triggered by 18a via the AMPK-PGC-1α pathway. As a result, our research highlights a thermogenic controlled polyphenol compound 18a and clarifies its underlying mechanisms, thus offering a potential strategy for the thermogenic targeting of adipose tissue to reduce the incidence of obesity and its related metabolic problems.

Angiogenesis-associated pathways play critical roles in neonatal sepsis outcomes

Neonatal sepsis is a major cause of childhood mortality. Limited diagnostic tools and mechanistic insights have hampered our abilities to develop prophylactic or therapeutic interventions. Biomarkers in human neonatal sepsis have been repeatedly identified as associated with dysregulation of angiopoietin signaling and altered arachidonic acid metabolism. We here provide the mechanistic evidence in support of the relevance for these observations. Angiopoetin-1 (Ang-1), which promotes vascular integrity, was decreased in blood plasma of human and murine septic newborns. In preclinical models, administration of Ang-1 provided prophylactic protection from septic death. Arachidonic acid metabolism appears to be functionally connected to Ang-1 via reactive oxygen species (ROS) with a direct role of nitric oxide (NO). Strengthening this intersection via oral administration of arachidonic acid and/or the NO donor L-arginine provided prophylactic as well as therapeutic protection from septic death while also increasing plasma Ang-1 levels among septic newborns. Our data highlight that targeting angiogenesis-associated pathways with interventions that increase Ang-1 activity directly or indirectly through ROS/eNOS provide promising avenues to prevent and/or treat severe neonatal sepsis.

Personalized whole-brain neural mass models reveal combined Aβ and tau hyperexcitable influences in Alzheimer’s disease

Neuronal dysfunction and cognitive deterioration in Alzheimer’s disease (AD) are likely caused by multiple pathophysiological factors. However, mechanistic evidence in humans remains scarce, requiring improved non-invasive techniques and integrative models. We introduce personalized AD computational models built on whole-brain Wilson-Cowan oscillators and incorporating resting-state functional MRI, amyloid-β (Aβ) and tau-PET from 132 individuals in the AD spectrum to evaluate the direct impact of toxic protein deposition on neuronal activity. This subject-specific approach uncovers key patho-mechanistic interactions, including synergistic Aβ and tau effects on cognitive impairment and neuronal excitability increases with disease progression. The data-derived neuronal excitability values strongly predict clinically relevant AD plasma biomarker concentrations (p-tau217, p-tau231, p-tau181, GFAP) and grey matter atrophy obtained through voxel-based morphometry. Furthermore, reconstructed EEG proxy quantities show the hallmark AD electrophysiological alterations (theta band activity enhancement and alpha reductions) which occur with Aβ-positivity and after limbic tau involvement. Microglial activation influences on neuronal activity are less definitive, potentially due to neuroimaging limitations in mapping neuroprotective vs detrimental activation phenotypes. Mechanistic brain activity models can further clarify intricate neurodegenerative processes and accelerate preventive/treatment interventions.

Nocturnal Heart Rate Response to Spontaneous Arousals Following Sleep Restriction

Short sleep duration is associated with future cardiovascular disease including hypertension, especially in females, but mechanistic evidence is largely lacking. Experimental sleep restriction has been shown to cause short sleep-mediated tachycardia and reduced heart rate variability, indicative of autonomic cardiac instability, in some but not all studies. Heart rate (HR) response to spontaneous cortical arousals can be regarded as an index of autonomic cardiac control given its characteristic temporal pattern. Whether the HR response to cortical arousals is altered during experimental sleep restriction remains unknown. We hypothesized that sleep restriction would result in augmented HR reactivity to spontaneous arousals, and that this response would be more marked in females. We studied 19 young, healthy subjects (eight females, age: 23.5 ± 5 years, body mass index [BMI]: 24.5 ± 3.6 kg/m2). In a randomized, crossover design, participants were tested during a normal sleep (NS, 9 hr sleep opportunity) or sleep restriction (SR, 4 hr sleep opportunity) study arm. Each 16-day study visit consisted of a 4-day study acclimation phase, 9-day experimental sleep perturbation segment, followed by a 3-day recovery period. An overnight polysomnography (PSG) study was conducted on study days 2, 5 and 11 (at baseline and after 1 and 7 days of restricted versus control sleep). A registered PSG technician provided sleep staging and spontaneous arousal scoring, which was confirmed by an investigator with sleep expertise (IMG). For each identified spontaneous arousal, the HR change was quantified for 30 cardiac cycles post-arousal onset and compared to a pre-arousal baseline (average HR 5 – 10 cardiac cycles prior to arousal). An arousal was considered valid for analysis if at least one minute of stage N2 or rapid eye movement (REM) sleep occurred following sleep stage transition and was at least 30 seconds apart from other sleep disturbance-related events (e.g., limb movement, apneic event, etc.). Given low prevalence of slow wave sleep (SWS) arousals, arousals occurring in that sleep stage were excluded from present analysis. Statistical analysis, including repeated measures ANOVA (RMANOVA, p < 0.05) with condition and time (cardiac cycles) as within-subjects factors and sex as the between-subjects factor, was conducted to compare the beat-to-beat HR response to arousal between study conditions. Additionally, average and peak HR responses to spontaneous arousals were compared via RMANOVA with condition and time (study days) as within-subjects and sex as between-subjects factors. HR response to spontaneous arousal in stage two and REM sleep was similar between NS and SR on study day 5 or day 11 (condition × time: p = 0.943, 0.865). Secondary analysis of average and peak HR responsiveness to spontaneous arousals in stage two and REM sleep between conditions and study days was also not statistically different (condition × time: p = 0.193, 0.185). Last, no significant sex differences were detected across comparisons (condition × time × sex: p > 0.05 for all). These findings suggest that a 9-day sleep restriction paradigm may not alter cardiac autonomic function in otherwise healthy adults. Future work is warranted to determine whether these results extend to individuals with established cardiovascular risk factors or cardiovascular disease. Support: NIH T32-DK007013, R01-114676, and CTSA grant UL1-TR002377. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Genetically proxied IL-6 receptor inhibition is associated with increased risk of atopic dermatitis

BackgroundDermatitis has been reported after initiation of IL-6 receptor inhibitors (IL-6Ri), while genetic association studies of atopic dermatitis (AD) have implicated IL-6R pathway signalling. However, causality remains unclear. As indications for IL-6Ri expand, so do the clinical importance of determining whether there is mechanistic evidence linking it to AD. ObjectiveTo examine the association between IL-6Ri and risk of AD. MethodsTo genetically mimic IL-6Ri, we selected single nucleotide polymorphisms within or near the IL6R gene associated with C-reactive protein (CRP) at genome-wide significance among 343,524 individuals. Genetic data for AD were obtained from 10,788 cases and 30,047 controls of European ancestry. We used the inverse-variance weighted and pleiotropy-robust methods and examined genetic confounding using colocalization. Analyses were replicated using 13,473 AD Finnish cases and 2,385 East Asian cases. Results from three independent analyses were pooled by meta-analysis. ResultsGenetically proxied IL-6Ri was associated with increased risk of AD (OR 1.78 per 4.4 mg/l reduction in CRP; 95%CI 1.28, 2.48; p=6.5x10-4). Results were replicated using Finnish outcome data (OR 2.07; 95%CI 1.58, 2.72; p=1.57x10-7), and Eastern Asian datasets (OR 1.68; 95%CI 1.12, 2.54; p=0.013). Meta-analysis of three independent populations (OR 1.89; 95%CI 1.57, 2.28; p=2.68x10-11) showed no statistical evidence of heterogeneity (p=0.65). We found no statistical evidence for pleiotropy or genetic confounding. ConclusionThis genetic investigation provides consistent evidence, across independent multi-ancestry populations, that IL-6R signalling is causally implicated in AD susceptibility. Clinicians should remain vigilant for adverse effects resembling AD when using IL-6R inhibitors for immune-mediated inflammatory diseases.