Treatment of hydrocephalus following posterior fossa tumor resection: a multicenter collaboration from the Hydrocephalus Clinical Research Network.

OBJECTIVE: Persistent hydrocephalus following posterior fossa brain tumor (PFBT) resection is a common cause of morbidity in pediatric brain tumor patients, for which the optimal treatment is debated. The purpose of this study was to compare treatment outcomes between VPS and ETV in patients with persistent hydrocephalus following surgical resection of a PFBT. METHODS: A post-hoc analysis was performed of the Hydrocephalus Clinical Research Network (HCRN) prospective observational study evaluating VPS and ETV for pediatric patients. Children who experienced hydrocephalus secondary to PFBT from 2008 to 2021 were included. Primary outcomes were VPS/ETV treatment failure and time-to-failure (TTF). RESULTS: Among 241 patients, the VPS (183) and ETV (58) groups were similar in age, extent of tumor resection, and preoperative ETV Success Score. There was no difference in overall treatment failure between VPS and ETV (33.9% vs 31.0%, p = 0.751). However, mean TTF was shorter for ETV than VPS (0.45 years vs 1.30 years, p = 0.001). While major complication profiles were similar, compared to VPS, ETV patients had relatively higher incidence of minor CSF leak (10.3% vs. 1.1%, p = 0.003) and pseudomeningocele (12.1% vs 3.3%, p = 0.02). No ETV failures were identified beyond 3 years, while shunt failures occurred beyond 5 years. Shunt infections occurred in 5.5% of the VPS cohort. CONCLUSIONS: ETV and VPS offer similar overall success rates for PFBT-related postoperative hydrocephalus. ETV failure occurs earlier, while susceptibility to VPS failure persists beyond 5 years. Tumor histology and grade may be considered when selecting the optimal means of CSF diversion.

Obstructive sleep apnoea and glaucoma: a systematic review and meta-analysis.

INTRODUCTION: Obstructive sleep apnoea (OSA) has been thought to be associated with glaucoma, however there are many conflicting studies on this topic. With many new studies having been published since the previous meta-analysis, we believe it is important to clarify this association. Hence, in this study we meta-analyse the recent literature regarding the association between OSA and glaucoma. METHODS: Pubmed, Embase, Scopus and Cochrane Library were searched from inception till the 28th February 2022 for observational as well as cross-sectional studies examining the association between OSA and glaucoma. Two reviewers selected studies, extracted data, graded the quality of included non-randomized studies using the Newcastle-Ottawa scale. The overall quality of evidence was assessed using GRADE. Random-effects models were used to meta-analyse the maximally covariate- adjusted associations. RESULTS: 48 studies were included in our systematic review, with 46 suitable for meta-analysis. Total study population was 4,566,984 patients. OSA was associated with a higher risk of glaucoma (OR 3.66, 95% CI 1.70 to 7.90, I2 = 98%, p < 0.01). After adjustment for various important confounders including age, gender and patient comorbidities such as hyperlipidaemia, hypertension, cardiovascular diseases and diabetes, patients with OSA had up to 40% higher odds of glaucoma. Substantial heterogeneity was eliminated through subgroup and sensitivity analyses after consideration of glaucoma subtype, OSA severity and adjustment for confounders. CONCLUSIONS: In this meta-analysis, OSA was associated with higher risk of glaucoma, as well as more severe ocular findings characteristic of the glaucomatous disease process. We suggest more clinical studies looking into the effects of OSA treatment on the progression of glaucoma to help clinical decision making for patients.

A biphasic model of lifespan in nematode Caenorhabditis elegans worm.

Ageing research focuses on identifying lifespan modifiers and understanding and appropriately interpreting their effects. One of the most relevant quantities being studied is the shape of the survival curve that can reveal crucial information on the mechanism of action. Here, we introduce a bilogistic model to describe the shape of the lifespan curves of Caenorhabditis elegans populations. Using the corrected Akaike information criterion and the RMSE as goodness-of-fit tests, we show that the bilogistic model provides a better fit to the experimental data from nematode worms than other mathematical models and can identify and confirm biphasic lifespan data. Our parametric model offers a method to interpret replicate experiments data in terms of the shape parameters of the lifespan curve and enables robust statistical analysis of intra- and inter-group variance. We apply the model to novel lifespan data from C. elegans and Drosophila melanogaster and provide a rational statistical analysis of lifespan modifiers such as temperature and daf-16/FOXO mutation.

Association between obstructive sleep apnea and floppy eyelid syndrome: A systematic review and metaanalysis.

RATIONALE: Obstructive sleep apnoea (OSA) has been linked to various ocular disorders, including floppy eyelid syndrome (FES). Previous studies have hypothesised the underlying association between the 2 , but results are currently still inconclusive. OBJECTIVE: To investigate the association between OSA and FES. METHODS: Four databases (Pubmed, Embase, Scopus, and Cochrane Library) were searched from inception until 28 February 2022 for observational studies and randomized controlled trials assessing the association between OSA and FES. Two reviewers selected studies, extracted data, graded the risk of bias using the Newcastle-Ottawa scale and the quality of assessment using the Grading of Recommendations Assessment, Development, and Evaluation system. Random-effects models were used to metaanalyze the associations. RESULTS: Twelve studies were included in the systematic review, of which nine were suitable for metaanalysis, with a combined cohort of 1,109 patients. Risk of bias was low to moderate. The overall analysis showed a significant positive association between OSA and FES (OR = 1.89, 95% CI = 1.27-2.83, I 2 = 44%). Further analysis revealed that the more severe the OSA was, the higher the risk of developing FES. Patients with severe OSA had the nominally highest risk of developing FES (OR = 3.06, 95% CI = 1.62-5.78, I 2 = 0%), followed by moderate OSA (OR = 2.53, 95% CI = 1.29-4.97, I 2 = 0%), and patients with mild OSA had the lowest risk (OR = 1.76, 95% CI = 0.85-3.62, I 2 = 0%). CONCLUSION: Our metaanalysis reports a positive association between OSA and FES, with increasing severity of OSA correlating with a significantly higher risk of FES. More longitudinal studies with sufficient duration of follow-up are needed to better characterise the relationship between OSA and FES.

Mendelian Randomization Implicates Bidirectional Association between Myopia and Primary Open-Angle Glaucoma or Intraocular Pressure.

PURPOSE: Observational studies suggest that myopic eyes carry a greater risk of primary open-angle glaucoma (POAG); however, the evidence for this association is inconsistent. This may be the result of confounding factors that arise from myopia that complicate clinical tests for glaucoma. This study used Mendelian randomization (MR) analysis to determine genetic causal associations among myopia, glaucoma, and glaucoma-related traits that overcome the effects of external confounders. DESIGN: Bidirectional genetic associations between myopia and refractive spherical equivalent (RSE), POAG, and POAG endophenotypes were investigated. PARTICIPANTS: Data from the largest publicly available genetic banks (n = 216,257-542,934) were analyzed. METHODS: Multiple MR models and multivariate genomic structural modeling to identify significant mediators for the relationship between myopia and POAG. MAIN OUTCOME MEASURES: Genetic causal associations between myopia and POAG and POAG endophenotypes. RESULTS: We found consistent bidirectional genetic associations between myopia and POAG and between myopia and intraocular pressure (IOP) using multiple MR models at Bonferroni-corrected levels of significance. Intraocular pressure showed the most significant mediation effect on RSE and POAG (Sobel test, 0.13; 95% confidence interval, 0.09-0.17; P = 1.37 × 10-8). CONCLUSIONS: A strong bidirectional genetic causal link exists between myopia and POAG that is mediated mainly by IOP. Our findings suggest that IOP-lowering treatment for glaucoma may be beneficial in myopic eyes, despite the challenges of establishing a clear clinical diagnosis. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Effects of Sodium/Glucose Cotransporter 2 (SGLT2) Inhibitors and Combined SGLT1/2 Inhibitors on Cardiovascular, Metabolic, Renal, and Safety Outcomes in Patients with Diabetes: A Network Meta-Analysis of 111 Randomized Controlled Trials.

INTRODUCTION: Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a class of anti-hyperglycemic drugs that has been steadily increasing in popularity due to its cardiovascular and renal benefits. Dual SGLT1/SGLT2 (SGLT1/2) inhibitors have potentially augmented anti-hyperglycemic action due to additional SGLT1 inhibition. This network meta-analysis aimed to compare the treatment effect across various outcomes between pure SGLT2 inhibitors and combined SGLT1/2 inhibitors in patients with diabetes. METHODOLOGY: Four electronic databases (PubMed, Embase, Cochrane, and Scopus) were searched for randomized controlled trials published from inception to 15th January 2022. Frequentist network meta-analysis was conducted to summarize the treatment effects reported in individual trials, stratified by type 1 (T1DM) and type 2 diabetes mellitus (T2DM). This meta-analysis was registered on PROSPERO (CRD42020222031). RESULTS: Our meta-analysis included 111 articles, comprising a combined cohort of 103,922 patients. SGLT2 inhibitors (dapagliflozin, empagliflozin, canagliflozin, ipragliflozin, ertugliflozin, and luseogliflozin) and SGLT1/2 inhibitors (licogliflozin and sotagliflozin) were compared. Frequentist network meta-analysis demonstrated that in T2DM patients, SGLT1/2 inhibitors led to a decreased hazard rate of myocardial infarction (hazard ratio [HR] 0.74, 95% confidence interval [CI] 0.56-0.98) and stroke (HR 0.65, 95% CI 0.47-0.92) compared with SGLT2 inhibitors. SGLT2 inhibitors achieved a greater hemoglobin A1c (HbA1c) reduction than SGLT1/2 inhibitors (0.16%, 95% CI 0.06-0.26). In patients with T2DM, the risk of diarrhea (risk ratio [RR] 1.42, 95% CI 1.07-1.88) and severe hypoglycemia (RR 5.89, 95% CI 1.41-24.57) were found to be higher with SGLT1/2 inhibitor use compared with SGLT2 inhibitor use. No differences were observed for cardiovascular, metabolic, and safety outcomes between SGLT1/2 inhibitors and SGLT2 inhibitors in patients with T1DM. CONCLUSIONS: In patients with T2DM, compared with pure SGLT2 inhibitors, combined SGLT1/2 inhibitors demonstrated a lower risk of myocardial infarction and of stroke, but were associated with a higher risk of diarrhea and severe hypoglycemia.

Effects of Sodium/Glucose Cotransporter Inhibitors on Atrial Fibrillation and Stroke: A Meta-Analysis.

OBJECTIVES: Recent clinical trials have shown the potential of sodium glucose cotransporter (SGLT) 2 inhibitors to reduce the risk of atrial fibrillation but not stroke. We conducted a systematic review and meta-analysis to clarify if SGLT2 or combined SGLT1/2 inhibitors affect the risk of atrial fibrillation and stroke in patients regardless of diabetic status. MATERIALS AND METHODS: Four electronic databases were searched on 21st November 2020 for studies evaluating outcomes of stroke and atrial fibrillation with SGLT2 or combined SGLT1/2 inhibitors in both diabetic and non-diabetic patients. Both random and fixed effect, pair-wise meta-analysis models were used to summarize the results of the studies. RESULTS: A total of 13 placebo-controlled, randomized-controlled trials were included. Eight trials comprising 35,702 patients were included in the analysis of atrial fibrillation outcomes and eight trials comprising 47,910 patients were included in the analysis of stroke outcomes. Patients on SGLT inhibitors, particularly SGLT2 inhibitors, had lower odds of atrial fibrillation (Peto odds ratio [95% confidence interval] = 0.76 [0.63-0.92]) compared to placebo. This effect remained significant with a follow-up duration longer than 1 year, in studies utilizing dapagliflozin, patients with type 2 diabetes mellitus, and patients with cardiovascular disease. No difference was observed in the odds of atrial fibrillation in patients with baseline heart failure. No effect was seen on the risk of stroke in patients taking SGLT inhibitors. CONCLUSIONS: SGLT2 inhibitors significantly reduced the odds of atrial fibrillation in diabetic patients. However, SGLT inhibitors did not significantly affect the risk of stroke.

Effects of Sodium-Glucose Cotransporter 2 on Amputation Events: A Systematic Review and Meta-Analysis of Randomized-Controlled Trials.

INTRODUCTION: Sodium-glucose cotransporter 2 (SGLT2) inhibitors are increasingly utilized in the treatment of diabetes mellitus as well as therapeutic extra-glycemic effects. However, there are still concerns over complications such as amputation events, given the results from the Canagliflozin Cardiovascular Assessment Study (CANVAS) trial. Hence, we conducted a systematic review and meta-analysis of randomized-controlled trials to investigate the effect of SGLT2 inhibitors on amputation events. METHODS: Four electronic databases (PubMed, Embase, Cochrane, and SCOPUS) were searched on November 21, 2020, for articles published from January 1, 2000, up to November 21, 2020, for studies that examined the effect of SGLT2 inhibitors on amputation events. Random-effect pair-wise meta-analysis for hazard ratios and fixed-effect Peto odds ratio meta-analysis were utilized to summarize the studies. RESULTS: A total of 15 randomized-controlled trials were included with a combined cohort of 63,716 patients. We demonstrated that there was no significant difference in amputation events across different types of SGLT2 inhibitors, different baseline populations, and different duration of SGLT2 inhibitor use. DISCUSSION/CONCLUSIONS: In this meta-analysis, SGLT2 inhibitors were not associated with a significant difference in amputation events.

SGLT inhibitors on weight and body mass: A meta-analysis of 116 randomized-controlled trials.

OBJECTIVE: Multiple trials have demonstrated the metabolic effects of sodium/glucose cotransporter 2 (SGLT2) inhibitors in patients regardless of diabetes status, and recent trials have been conducted on the combined sodium/glucose cotransporter 1 and sodium/glucose cotransporter 2 (SGLT1/SGLT2) inhibitors. Therefore, a meta-analysis was conducted to investigate the weight reduction effects and dose-response relationship of SGLT inhibitors and to assess the relative efficacy of SGLT1/SGLT2 inhibitors. METHODS: Four electronic databases (PubMed, Embase, Cochrane, and Scopus) were searched on November 21, 2020, for articles published from January 1, 2000, up to November 21, 2020. RESULTS: In total, 116 randomized-controlled trials were included, with a combined cohort of 98,497 patients. Overall, patients had a mean weight reduction of -1.79 kg (95% CI: -1.93 to -1.66, p < 0.001) compared with placebo. This effect was observed across diabetes status, duration of follow-up, various comorbidities, and all SGLT drug types. Mean BMI changes were -0.71 kg/m2 (95% CI: -0.94 to -0.47, p < 0.001) compared with placebo. Canagliflozin, empagliflozin, sotagliflozin, and licogliflozin showed a dose-response relationship for mean weight change. Compared with SGLT2 inhibitors, SGLT1/SGLT2 inhibitors had a significantly larger reduction in weight. CONCLUSIONS: SGLT inhibitors demonstrated weight reduction benefits in this meta-analysis. Further studies are needed to clarify their role in weight management.

Obstructive Sleep Apnea and Lung Cancer: A Systematic Review and Meta-Analysis.

Rationale: In 2020, lung cancer was the leading cause of cancer deaths and the most common cancer in men. Although obstructive sleep apnea (OSA) has been postulated to be carcinogenic, epidemiological studies are inconclusive. Objectives: To investigate the associations between OSA and the incidence and mortality of lung cancer. Methods: Four electronic databases (PubMed, Embase, Cochrane Library, and Scopus) were searched from inception until 6 June 2021 for randomized controlled trials and observational studies examining the association between sleep apnea and incident lung cancer. Two reviewers selected studies, extracted data, graded the risk of bias using the Newcastle-Ottawa scale and the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation system. Random-effects models were used to meta-analyze the maximally covariate-adjusted associations. Results: Seven studies were included in our systematic review, among which four were suitable for meta-analysis, comprising a combined cohort of 4,885,518 patients. Risk of bias was low to moderate. OSA was associated with a higher incidence of lung cancer (hazard ratio, 1.25; 95% confidence interval, 1.02-1.53), with substantial heterogeneity (I2 = 97%). Heterogeneity was eliminated, with a stable pooled effect size, when including the three studies with at least 5 years of median follow-up (hazard ratio, 1.32; 95% confidence interval, 1.27-1.37; I2 = 0%). Conclusions: In this meta-analysis of 4,885,518 patients from four observational studies, patients with OSA had an approximately 30% higher risk of lung cancer compared with those without OSA. We suggest more clinical studies with longer follow-up as well as biological models of lung cancer be performed to further elucidate this relationship.

Comparing Sacubitril/Valsartan Against Sodium-Glucose Cotransporter 2 Inhibitors in Heart Failure: A Systematic Review and Network Meta-analysis.

BACKGROUND AND OBJECTIVE: In recent trials, sodium-glucose cotransporter 2 (SGLT2) inhibitors proved effective as treatment for heart failure. However, the relative efficacy of sacubitril/valsartan against SGLT2 inhibitor in patients with heart failure remains unknown. Hence, we performed a network meta-analysis to compare the effects of sacubitril/valsartan against SGLT2 inhibitors on cardiovascular outcomes in patients with heart failure. METHODS: Four electronic databases (PubMed, Embase, Cochrane, SCOPUS) were searched for randomised-controlled trials (RCTs) published from 1st January 2000 to 25th September 2021. Two additional systematic reviews were conducted for RCTs of enalapril and valsartan to establish a common comparator arm. Frequentist network meta-analysis models were utilised to summarise the studies. RESULTS: Twenty-five RCTs were included, comprising a combined cohort of 47,275 patients. Network meta-analysis demonstrated that compared to SGLT2 inhibitors, sacubitril/valsartan achieved a larger hazard rate reduction in the composite of heart failure hospitalisation and cardiovascular death (hazard ratio [HR]: 0.86; 95% CI 0.75-0.98), cardiovascular death (HR: 0.78; 95% CI 0.65-0.94), and a larger mean change in systolic blood pressure at 8 or more months (weighted mean difference [WMD]: - 7.08 mmHg; 95% CI - 8.28 to - 5.89). There were no significant differences in treatment effects across heart failure hospitalisation, all-cause mortality, diastolic blood pressure at 12 weeks, and systolic blood pressure at 2-4 months. In patients with heart failure with reduced ejection fraction, sacubitril/valsartan achieved a 20% hazard rate reduction for cardiovascular death compared to SGLT2 inhibitors. CONCLUSIONS: In patients with heart failure, sacubitril/valsartan was demonstrated to be superior to SGLT2 inhibitors in the treatment effect for the composite of heart failure hospitalisation and cardiovascular death, cardiovascular death, and long-term blood pressure.

Acquisition of Temporal HIF Transcriptional Activity Using a Secreted Luciferase Assay.

Here we describe a simple method based on secreted luciferase driven by a hypoxia-inducible factor (HIF) response element (HRE) that allows the acquisition of dynamic and high-throughput data on HIF transcriptional activity during hypoxia and pharmacological activation of HIF. The sensitivity of the assay allows for the secreted luciferase to be consecutively sampled (as little as 1% of the total supernatant) over an extended time period, thus allowing the acquisition of time-resolved HIF transcriptional activity.

The regulation of transcriptional repression in hypoxia.

A sufficient supply molecular oxygen is essential for the maintenance of physiologic metabolism and bioenergetic homeostasis for most metazoans. For this reason, mechanisms have evolved for eukaryotic cells to adapt to conditions where oxygen demand exceeds supply (hypoxia). These mechanisms rely on the modification of pre-existing proteins, translational arrest and transcriptional changes. The hypoxia inducible factor (HIF; a master regulator of gene induction in response to hypoxia) is responsible for the majority of induced gene expression in hypoxia. However, much less is known about the mechanism(s) responsible for gene repression, an essential part of the adaptive transcriptional response. Hypoxia-induced gene repression leads to a reduction in energy demanding processes and the redirection of limited energetic resources to essential housekeeping functions. Recent developments have underscored the importance of transcriptional repressors in cellular adaptation to hypoxia. To date, at least ten distinct transcriptional repressors have been reported to demonstrate sensitivity to hypoxia. Central among these is the Repressor Element-1 Silencing Transcription factor (REST), which regulates over 200 genes. In this review, written to honor the memory and outstanding scientific legacy of Lorenz Poellinger, we provide an overview of our existing knowledge with respect to transcriptional repressors and their target genes in hypoxia.

Three-factor models versus time series models: quantifying time-dependencies of interactions between stimuli in cell biology and psychobiology for short longitudinal data.

Signal integration determines cell fate on the cellular level, affects cognitive processes and affective responses on the behavioural level, and is likely to be involved in psychoneurobiological processes underlying mood disorders. Interactions between stimuli may subjected to time effects. Time-dependencies of interactions between stimuli typically lead to complex cell responses and complex responses on the behavioural level. We show that both three-factor models and time series models can be used to uncover such time-dependencies. However, we argue that for short longitudinal data the three factor modelling approach is more suitable. In order to illustrate both approaches, we re-analysed previously published short longitudinal data sets. We found that in human embryonic kidney 293 cells cells the interaction effect in the regulation of extracellular signal-regulated kinase (ERK) 1 signalling activation by insulin and epidermal growth factor is subjected to a time effect and dramatically decays at peak values of ERK activation. In contrast, we found that the interaction effect induced by hypoxia and tumour necrosis factor-alpha for the transcriptional activity of the human cyclo-oxygenase-2 promoter in HEK293 cells is time invariant at least in the first 12-h time window after stimulation. Furthermore, we applied the three-factor model to previously reported animal studies. In these studies, memory storage was found to be subjected to an interaction effect of the beta-adrenoceptor agonist clenbuterol and certain antagonists acting on the alpha-1-adrenoceptor / glucocorticoid-receptor system. Our model-based analysis suggests that only if the antagonist drug is administer in a critical time window, then the interaction effect is relevant.

Hydroxylase inhibition regulates inflammation-induced intestinal fibrosis through the suppression of ERK-mediated TGF-ß1 signaling. [corrected].

Fibrosis is a complication of chronic inflammatory disorders such as inflammatory bowel disease, a condition which has limited therapeutic options and often requires surgical intervention. Pharmacologic inhibition of oxygen-sensing prolyl hydroxylases, which confer oxygen sensitivity upon the hypoxia-inducible factor pathway, has recently been shown to have therapeutic potential in colitis, although the mechanisms involved remain unclear. Here, we investigated the impact of hydroxylase inhibition on inflammation-driven fibrosis in a murine colitis model. Mice exposed to dextran sodium sulfate, followed by a period of recovery, developed intestinal fibrosis characterized by alterations in the pattern of collagen deposition and infiltration of activated fibroblasts. Treatment with the hydroxylase inhibitor dimethyloxalylglycine ameliorated fibrosis. TGF-ß1 is a key regulator of fibrosis that acts through the activation of fibroblasts. Hydroxylase inhibition reduced TGF-ß1-induced expression of fibrotic markers in cultured fibroblasts, suggesting a direct role for hydroxylases in TGF-ß1 signaling. This was at least in part due to inhibition of noncanonical activation of extracellular signal-regulated kinase (ERK) signaling. In summary, pharmacologic hydroxylase inhibition ameliorates intestinal fibrosis through suppression of TGF-ß1-dependent ERK activation in fibroblasts. We hypothesize that in addition to previously reported immunosupressive effects, hydroxylase inhibitors independently suppress profibrotic pathways.

REST is a hypoxia-responsive transcriptional repressor.

Cellular exposure to hypoxia results in altered gene expression in a range of physiologic and pathophysiologic states. Discrete cohorts of genes can be either up- or down-regulated in response to hypoxia. While the Hypoxia-Inducible Factor (HIF) is the primary driver of hypoxia-induced adaptive gene expression, less is known about the signalling mechanisms regulating hypoxia-dependent gene repression. Using RNA-seq, we demonstrate that equivalent numbers of genes are induced and repressed in human embryonic kidney (HEK293) cells. We demonstrate that nuclear localization of the Repressor Element 1-Silencing Transcription factor (REST) is induced in hypoxia and that REST is responsible for regulating approximately 20% of the hypoxia-repressed genes. Using chromatin immunoprecipitation assays we demonstrate that REST-dependent gene repression is at least in part mediated by direct binding to the promoters of target genes. Based on these data, we propose that REST is a key mediator of gene repression in hypoxia.

REST mediates resolution of HIF-dependent gene expression in prolonged hypoxia.

The hypoxia-inducible factor (HIF) is a key regulator of the cellular response to hypoxia which promotes oxygen delivery and metabolic adaptation to oxygen deprivation. However, the degree and duration of HIF-1α expression in hypoxia must be carefully balanced within cells in order to avoid unwanted side effects associated with excessive activity. The expression of HIF-1α mRNA is suppressed in prolonged hypoxia, suggesting that the control of HIF1A gene transcription is tightly regulated by negative feedback mechanisms. Little is known about the resolution of the HIF-1α protein response and the suppression of HIF-1α mRNA in prolonged hypoxia. Here, we demonstrate that the Repressor Element 1-Silencing Transcription factor (REST) binds to the HIF-1α promoter in a hypoxia-dependent manner. Knockdown of REST using RNAi increases the expression of HIF-1α mRNA, protein and transcriptional activity. Furthermore REST knockdown increases glucose consumption and lactate production in a HIF-1α- (but not HIF-2α-) dependent manner. Finally, REST promotes the resolution of HIF-1α protein expression in prolonged hypoxia. In conclusion, we hypothesize that REST represses transcription of HIF-1α in prolonged hypoxia, thus contributing to the resolution of the HIF-1α response.

Species differential regulation of COX2 can be described by an NFκB-dependent logic AND gate.

Cyclooxygenase 2 (COX2), a key regulatory enzyme of the prostaglandin/eicosanoid pathway, is an important target for anti-inflammatory therapy. It is highly induced by pro-inflammatory cytokines in a Nuclear factor kappa B (NFκB)-dependent manner. However, the mechanisms determining the amplitude and dynamics of this important pro-inflammatory event are poorly understood. Furthermore, there is significant difference between human and mouse COX2 expression in response to the inflammatory stimulus tumor necrosis factor alpha (TNFα). Here, we report the presence of a molecular logic AND gate composed of two NFκB response elements (NREs) which controls the expression of human COX2 in a switch-like manner. Combining quantitative kinetic modeling and thermostatistical analysis followed by experimental validation in iterative cycles, we show that the human COX2 expression machinery regulated by NFκB displays features of a logic AND gate. We propose that this provides a digital, noise-filtering mechanism for a tighter control of expression in response to TNFα, such that a threshold level of NFκB activation is required before the promoter becomes active and initiates transcription. This NFκB-regulated AND gate is absent in the mouse COX2 promoter, most likely contributing to its differential graded response in promoter activity and protein expression to TNFα. Our data suggest that the NFκB-regulated AND gate acts as a novel mechanism for controlling the expression of human COX2 to TNFα, and its absence in the mouse COX2 provides the foundation for further studies on understanding species-specific differential gene regulation.