ß-cell-selective inhibition of DNA damage response signaling by nitric oxide is associated with an attenuation in glucose uptake.

Nitric oxide (NO) plays a dual role in regulating DNA damage response (DDR) signaling in pancreatic ß-cells. As a genotoxic agent, NO activates two types of DDR signaling; however, when produced at micromolar levels by the inducible isoform of NO synthase, NO inhibits DDR signaling and DDR-induced apoptosis in a ß-cell-selective manner. DDR signaling inhibition by NO correlates with mitochondrial oxidative metabolism inhibition and decreases in ATP and NAD+. Unlike most cell types, ß-cells do not compensate for impaired mitochondrial oxidation by increasing glycolytic flux, and this metabolic inflexibility leads to a decrease in ATP and NAD+. Here, we used multiple analytical approaches to determine changes in intermediary metabolites in ß-cells and non-ß-cells treated with NO or complex I inhibitor rotenone. In addition to ATP and NAD+, glycolytic and tricarboxylic acid cycle intermediates as well as NADPH are significantly decreased in ß-cells treated with NO or rotenone. Consistent with glucose-6-phosphate residing at the metabolic branchpoint for glycolysis and the pentose phosphate pathway (NADPH), we show that mitochondrial oxidation inhibitors limit glucose uptake in a ß-cell-selective manner. Our findings indicate that the ß-cell-selective inhibition of DDR signaling by NO is associated with a decrease in ATP to levels that fall significantly below the KM for ATP of glucokinase (glucose uptake) and suggest that this action places the ß-cell in a state of suspended animation where it is metabolically inert until NO is removed, and metabolic function can be restored.

ß-Cell-selective regulation of gene expression by nitric oxide.

Nitric oxide is produced at low micromolar levels following the induction of inducible nitric oxide synthase (iNOS) and is responsible for mediating the inhibitory actions of cytokines on glucose-stimulated insulin secretion by islets of Langerhans. It is through the inhibition of mitochondrial oxidative metabolism, specifically aconitase and complex 4 of the electron transport chain, that nitric oxide inhibits insulin secretion. Nitric oxide also attenuates protein synthesis, induces DNA damage, activates DNA repair pathways, and stimulates stress responses (unfolded protein and heat shock) in ß-cells. In this report, the time- and concentration-dependent effects of nitric oxide on the expression of six genes known to participate in the response of ß-cells to this free radical were examined. The genes included Gadd45α (DNA repair), Puma (apoptosis), Hmox1 (antioxidant defense), Hsp70 (heat shock), Chop (UPR), and Ppargc1α (mitochondrial biogenesis). We show that nitric oxide stimulates ß-cell gene expression in a narrow concentration range of ∼0.5-1 µM or levels corresponding to iNOS-derived nitric oxide. At concentrations greater than 1 µM, nitric oxide fails to stimulate gene expression in ß-cells, and this is associated with the inhibition of mitochondrial oxidative metabolism. This narrow concentration range of responses is ß-cell selective, as the actions of nitric oxide in non-ß-cells (α-cells, mouse embryonic fibroblasts, and macrophages) are concentration dependent. Our findings suggest that ß-cells respond to a narrow concentration range of nitric oxide that is consistent with the levels produced following iNOS induction, and that these concentration-dependent actions are selective for insulin-containing cells.

Zinc-chelating BET bromodomain inhibitors equally target islet endocrine cell types.

Inhibition of the bromodomain and extraterminal domain (BET) protein family is a potential strategy to prevent and treat diabetes; however, the clinical use of BET bromodomain inhibitors (BETis) is associated with adverse effects. Here, we explore a strategy for targeting BETis to ß cells by exploiting the high-zinc (Zn2+) concentration in ß cells relative to other cell types. We report the synthesis of a novel, Zn2+-chelating derivative of the pan-BETi (+)-JQ1, (+)-JQ1-DPA, in which (+)-JQ1 was conjugated to dipicolyl amine (DPA). As controls, we synthesized (+)-JQ1-DBA, a non-Zn2+-chelating derivative, and (-)-JQ1-DPA, an inactive enantiomer that chelates Zn2+. Molecular modeling and biophysical assays showed that (+)-JQ1-DPA and (+)-JQ1-DBA retain potent binding to BET bromodomains in vitro. Cellular assays demonstrated (+)-JQ1-DPA attenuated NF-ĸB target gene expression in ß cells stimulated with the proinflammatory cytokine interleukin 1ß. To assess ß-cell selectivity, we isolated islets from a mouse model that expresses green fluorescent protein in insulin-positive ß cells and mTomato in insulin-negative cells (non-ß cells). Surprisingly, Zn2+ chelation did not confer ß-cell selectivity as (+)-JQ1-DPA was equally effective in both ß and α cells; however, (+)-JQ1-DPA was less effective in macrophages, a nonendocrine islet cell type. Intriguingly, the non-Zn2+-chelating derivative (+)-JQ1-DBA displayed the opposite selectivity, with greater effect in macrophages compared with (+)-JQ1-DPA, suggesting potential as a macrophage-targeting molecule. These findings suggest that Zn2+-chelating small molecules confer endocrine cell selectivity rather than ß-cell selectivity in pancreatic islets and provide valuable insights and techniques to assess Zn2+ chelation as an approach to selectively target small molecules to pancreatic ß cells.NEW & NOTEWORTHY Inhibition of BET bromodomains is a novel potential strategy to prevent and treat diabetes mellitus. However, BET inhibitors have negative side effects. We synthesized a BET inhibitor expected to exploit the high zinc concentration in ß cells to accumulate in ß cells. We show our inhibitor targeted pancreatic endocrine cells; however, it was less effective in immune cells. A control inhibitor showed the opposite effect. These findings help us understand how to target specific cells in diabetes treatment.

Third time's a charm: band to sleeve to bypass.

BACKGROUND: Adjustable gastric bands (AGB) are frequently converted to sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) due to weight recurrence or band complications. Such conversions carry a higher-risk than primary procedures. Some patients undergo two conversions-from AGB to SG, and subsequently from SG to RYGB. This presents a unique situation with limited literature on indications and complication rates associated with these double conversions. METHODS: We examined the 2020-2021 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) Participant Use File to evaluate conversions from AGB to SG and then to RYGB. Patient and operative characteristics, along with outcomes, were evaluated. Descriptive statistics were applied. RESULTS: We identified 276 patients who underwent a conversion from AGB to SG and then to RYGB. The primary reason for the second conversion (SG to RYGB) was gastroesophageal reflux disease (GERD) at 55.1%, followed by inadequate weight loss or weight regain (IWL/WR) at 36.9%. The remaining reasons included dysphagia, nausea, vomiting, or others. Patients converted for IWL/WR demonstrated a higher baseline body mass index and prevalence of sleep apnea compared to other cohorts (both p < 0.001). Meanwhile, patients in the "other reasons" group had the highest rate of open surgical approaches (9.1%) and concurrent lysis of adhesions (p = 0.001 and p = 0.022), with correspondingly higher rates of anastomotic leak, reoperations, serious complications, and mortality. CONCLUSIONS: Patients undergoing double conversions (AGB to SG to RYGB) do so primarily for GERD or IWL/WR. Further research is required to better define the optimal primary operation for each patient, aiming to reduce the necessity for multiple conversions.

Tourniquet Use in Extremity-Based Microsurgery.

BACKGROUND: The use of tourniquets and their role in extremity-based microsurgery has not been thoroughly investigated. The purpose of this study was to investigate tourniquet use and its associated outcomes and complications. The authors hypothesize that tourniquets enhance visualization, bloodless approaches to vessel harvest, flap elevation, and anastomosis without added complications. METHODS: A retrospective chart review was completed for patients who had undergone extremity-based microsurgery with the use of a tourniquet between January 2018 and February 2022 at two large academic institutions. Demographic characteristics, initial reasons for surgery, complications, and outcomes were recorded. Patients were separated into groups based on tourniquet use during three operative segments: (1) flap elevation, (2) vessel harvest, and (3) microvascular anastomosis. An internal comparison of complication rate was performed between cases for which a tourniquet was used for one operative segment to all cases in which it was not used for the same operative segment. Univariate and multivariate statistical analyses were performed to identify statistically significant results. RESULTS: A total of 99 patients (106 surgeries) were included in this study across sites. The mean age was 41.2 years and 67.7% of the patients were male. The most common reason for microsurgical reconstruction was trauma (50.5%). The need for an additional unplanned surgery was the most common surgical complication (16%). A total of 70, 61, and 32% of procedures used a tourniquet for flap elevation, vessel harvest, and for anastomosis, respectively. Statistical analyses identified no difference in complication rates for procedures for which a tourniquet was or was not used for interventions. CONCLUSION: Based on these results, the authors state that tourniquets can be utilized for extremity-based microsurgery to enable bloodless dissection without the concern of increased complication rates.

Macroergonomic components of the patient work system shaping dyadic care management during adolescence: a case study of type 1 diabetes.

The role of the social, physical, and organisational environments in shaping how patients and their caregivers perform work remains largely unexplored in human factors/ergonomics literature. This study recruited 19 dyads consisting of a parent and their child with type 1 diabetes to be interviewed individually and analysed using a macroergonomic framework. Our findings aligned with the macroergonomic factors as presented in previous models, while highlighting the need to expand upon certain components to gain a more comprehensive representation of the patient work system as relevant to dyadic management. Examples of design efforts that should follow from these findings include expanding existing data sharing options to include information from the external environment and capitalising on the capabilities of artificial intelligence as a decision support system. Future research should focus on longitudinally assessing patient work systems throughout transition periods in addition to more explicitly exploring the roles of social network members.

Work performed by patients and their caregivers is shaped by the social, physical, and organisational contexts they are embedded within. This paper explored how adolescents with type 1 diabetes managed their health alongside their parents in the context of these macroergonomic factors. These findings have implications for research and design.

Content Validity Testing of a Novel Cognitive Screen, the Gaylord Occupational Therapy Cognitive (GOT-Cog), to Improve Inpatient Occupational Therapy Treatment Planning.

IMPORTANCE: No single cognitive screen adequately captures all cognitive domains that are important for inpatient occupational therapy treatment planning. OBJECTIVE: To quantify the content validity of a novel 22-item cognitive screen, the Gaylord Occupational Therapy Cognitive (GOT-Cog) screen, developed to better inform inpatient occupational therapy treatment planning. DESIGN: Delphi-style expert panel review. SETTING: Long-term acute care hospital. PARTICIPANTS: The first panel was attended by four occupational therapists, two speech-language pathologists, one physician assistant, and two neuropsychologists; the second, by four occupational therapists, one speech-language pathologist, and one physician assistant. INTERVENTION: Each Delphi panel discussed the relevance, essentiality, and clarity of each item. After each discussion, panelists completed a content validity survey to summarize their evaluation of each item. OUTCOMES AND MEASURES: On the basis of panelists' survey responses, item- and scale-level relevance, essentiality, and clarity were quantified by calculating the respective content validity index (CVI), content validity ratio (CVR), and content clarity index (CCI). Universal agreement (UA) and κ statistics were also calculated, as appropriate. RESULTS: Upon presenting the initial 23-item instrument covering 10 cognitive domains to the first Delphi panel, several questions were added, removed, or rewritten, resulting in a 22-item instrument representing nine domains. After the second panel, several questions were again rewritten, and the domains reorganized. All scale-level metrics improved, including CVI (from 0.87 to 1.0), UA (0.52 to 1.0), CVR (0.43 to 0.94), and CCI (2.26 to 2.92). CONCLUSIONS AND RELEVANCE: GOT-Cog displays overall excellent content validity and can proceed to construct validity testing. Plain-Language Summary: By reporting on the content validity of the Gaylord Occupational Therapy Cognitive screen, this brief report begins the necessary process of evaluating the measure's overall validity and reliability.

Effect of operative times in bariatric surgery on outcomes: a matched analysis of the MBSAQIP database.

BACKGROUND: The implications of operative time (OT) have been studied in different surgical specialties, showing a correlation with higher incidence rates of postoperative complications. However, the impact of OT on bariatric surgery complications is not well elucidated. METHODS: A retrospective review of the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program database between 2015 and 2019 was performed. A total of 358,382 SG patients and 123,357 RYGB patients were included. The median OT was 68 min (10-720) and 113 min (10-640) for the sleeve gastrectomy (SG) group and the Roux-en-Y gastric bypass group, respectively. The groups were subdivided into two subgroups based on OT in comparison to the median time of each group. The subgroups were compared for surgical complications and outcomes. To reduce selection bias and risk of confounders, we performed a propensity score matching (PSM) for 22 variables. RESULTS: In the PSM-matched cohort, 18,915 SG and 6,495 RYGB patients were included in each subgroup. The SG cohort showed higher rates of Clavien-Dindo Class 1, 2, 3a, 4, and 5 complications as well as higher rates of readmission, reoperation, and reintervention in the longer OT group before matching. After PSM, the subgroup with longer times continued to have higher rates of Clavien-Dindo Class 2 complications and higher rates of readmission and reoperation. Similarly, there were higher rates of all Clavien-Dindo class complications as well as readmission, reoperation, and reintervention in the RYGB group with higher OT. After PSM, there were still higher rates of Clavien-Dindo Class 3a complications as well as readmission and reintervention in the RYGB subgroup with prolonged OT. CONCLUSION: In both SG and RYGB, longer OT was associated with increased rates of complications as well as readmission, reoperation, and reintervention. Surgeons should be cognizant of the increased rates of complications when operative times are longer.

Duodenal switch without versus with laparoscopic cholecystectomy: a perioperative risk comparative analysis of the MBSAQIP database (2015-2019).

BACKGROUND: The results of concurrent cholecystectomy with Roux-en Y gastric bypass and sleeve gastrectomy have been well elucidated. Large-scale data on the outcomes of concomitant cholecystectomy during biliopancreatic diversion with duodenal switch (BPD-DS) are still lacking. Our study aimed to explore whether simultaneous cholecystectomy with BPD-DS alters the 30-day postoperative outcomes. METHODS: We conducted a retrospective analysis of the MBSAQIP database between 2015 and 2019. Propensity-score matching (PSM) in BPD-DS with cholecystectomy (Group 1) and BPD-DS without cholecystectomy (Group 2) cohorts was performed (PSM ratio 1:2). The two groups were matched for a total of 21 baseline variables including age, gender, BMI, ASA class, and other medical comorbidities and conditions. The 30-day postoperative morbidity, mortality, reoperation, reintervention, and readmissions were obtained. RESULTS: Initially, 568 patients in Group 1 and 5079 in Group 2 were identified. After performing PSM, 564 and 1128 patients respectively were compared. The BPD-DS with cholecystectomy group reported a higher rate of reoperation and reintervention compared to BPD-DS alone (3.9% versus 2.4% and 3.2% versus 2%, respectively), even though it did not reach statistical significance. The intervention time was significantly higher in Group 1 compared to Group 2 (192.4 ± 77.6 versus 126.4 ± 61.4 min). Clavien-Dindo complications (1-5) were similar between these two PSM cohorts. CONCLUSION: Concomitant cholecystectomy during BPD-DS increases operative times but does not affect the other outcomes. Based on our results, the decision of cholecystectomy at the time of BPD-DS should be left to the surgeon's judgment.

Regulation of ATR-dependent DNA damage response by nitric oxide.

We have shown that nitric oxide limits ataxia-telangiectasia mutated signaling by inhibiting mitochondrial oxidative metabolism in a ß-cell selective manner. In this study, we examined the actions of nitric oxide on a second DNA damage response transducer kinase, ataxia-telangiectasia and Rad3-related protein (ATR). In ß-cells and non-ß-cells, nitric oxide activates ATR signaling by inhibiting ribonucleotide reductase; however, when produced at inducible nitric oxide synthase-derived (low micromolar) levels, nitric oxide impairs ATR signaling in a ß-cell selective manner. The inhibitory actions of nitric oxide are associated with impaired mitochondrial oxidative metabolism and lack of glycolytic compensation that result in a decrease in ß-cell ATP. Like nitric oxide, inhibitors of mitochondrial respiration reduce ATP levels and limit ATR signaling in a ß-cell selective manner. When non-ß-cells are forced to utilize mitochondrial oxidative metabolism for ATP generation, their response is more like ß-cells, as nitric oxide and inhibitors of mitochondrial respiration attenuate ATR signaling. These studies support a dual role for nitric oxide in regulating ATR signaling. Nitric oxide activates ATR in all cell types examined by inhibiting ribonucleotide reductase, and in a ß-cell selective manner, inducible nitric oxide synthase-derived levels of nitric oxide limit ATR signaling by attenuating mitochondrial oxidative metabolism and depleting ATP.

The autoimmunity-associated gene PTPN22 potentiates toll-like receptor-driven, type 1 interferon-dependent immunity.

Immune cells sense microbial products through Toll-like receptors (TLR), which trigger host defense responses including type 1 interferons (IFNs) secretion. A coding polymorphism in the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is a susceptibility allele for human autoimmune and infectious disease. We report that Ptpn22 selectively regulated type 1 IFN production after TLR engagement in myeloid cells. Ptpn22 promoted host antiviral responses and was critical for TLR agonist-induced, type 1 IFN-dependent suppression of inflammation in colitis and arthritis. PTPN22 directly associated with TNF receptor-associated factor 3 (TRAF3) and promotes TRAF3 lysine 63-linked ubiquitination. The disease-associated PTPN22W variant failed to promote TRAF3 ubiquitination, type 1 IFN upregulation, and type 1 IFN-dependent suppression of arthritis. The findings establish a candidate innate immune mechanism of action for a human autoimmunity "risk" gene in the regulation of host defense and inflammation.

Inhibition of oxidative metabolism by nitric oxide restricts EMCV replication selectively in pancreatic beta-cells.

Environmental factors, such as viral infection, are proposed to play a role in the initiation of autoimmune diabetes. In response to encephalomyocarditis virus (EMCV) infection, resident islet macrophages release the pro-inflammatory cytokine IL-1ß, to levels that are sufficient to stimulate inducible nitric oxide synthase (iNOS) expression and production of micromolar levels of the free radical nitric oxide in neighboring ß-cells. We have recently shown that nitric oxide inhibits EMCV replication and EMCV-mediated ß-cell lysis and that this protection is associated with an inhibition of mitochondrial oxidative metabolism. Here we show that the protective actions of nitric oxide against EMCV infection are selective for ß-cells and associated with the metabolic coupling of glycolysis and mitochondrial oxidation that is necessary for insulin secretion. Inhibitors of mitochondrial respiration attenuate EMCV replication in ß-cells, and this inhibition is associated with a decrease in ATP levels. In mouse embryonic fibroblasts (MEFs), inhibition of mitochondrial metabolism does not modify EMCV replication or decrease ATP levels. Like most cell types, MEFs have the capacity to uncouple the glycolytic utilization of glucose from mitochondrial respiration, allowing for the maintenance of ATP levels under conditions of impaired mitochondrial respiration. It is only when MEFs are forced to use mitochondrial oxidative metabolism for ATP generation that mitochondrial inhibitors attenuate viral replication. In a ß-cell selective manner, these findings indicate that nitric oxide targets the same metabolic pathways necessary for glucose stimulated insulin secretion for protection from viral lysis.

Inhibition of mitochondrial oxidative metabolism attenuates EMCV replication and protects ß-cells from virally mediated lysis.

Viral infection is one environmental factor that may contribute to the initiation of pancreatic ß-cell destruction during the development of autoimmune diabetes. Picornaviruses, such as encephalomyocarditis virus (EMCV), induce a pro-inflammatory response in islets leading to local production of cytokines, such as IL-1, by resident islet leukocytes. Furthermore, IL-1 is known to stimulate ß-cell expression of iNOS and production of the free radical nitric oxide. The purpose of this study was to determine whether nitric oxide contributes to the ß-cell response to viral infection. We show that nitric oxide protects ß-cells against virally mediated lysis by limiting EMCV replication. This protection requires low micromolar, or iNOS-derived, levels of nitric oxide. At these concentrations nitric oxide inhibits the Krebs enzyme aconitase and complex IV of the electron transport chain. Like nitric oxide, pharmacological inhibition of mitochondrial oxidative metabolism attenuates EMCV-mediated ß-cell lysis by inhibiting viral replication. These findings provide novel evidence that cytokine signaling in ß-cells functions to limit viral replication and subsequent ß-cell lysis by attenuating mitochondrial oxidative metabolism in a nitric oxide-dependent manner.

The location of sensing determines the pancreatic ß-cell response to the viral mimetic dsRNA.

Viral infection is an environmental trigger that has been suggested to initiate pancreatic ß-cell damage, leading to the development of autoimmune diabetes. Viruses potently activate the immune system and can damage ß cells by either directly infecting them or stimulating the production of secondary effector molecules (such as proinflammatory cytokines) during bystander activation. However, how and where ß cells recognize viruses is unclear, and the antiviral responses that are initiated following virus recognition are incompletely understood. In this study, we show that the ß-cell response to dsRNA, a viral replication intermediate known to activate antiviral responses, is determined by the cellular location of sensing (intracellular versus extracellular) and differs from the cellular response to cytokine treatment. Using biochemical and immunological methods, we show that ß cells selectively respond to intracellular dsRNA by expressing type I interferons (IFNs) and inducing apoptosis, but that they do not respond to extracellular dsRNA. These responses differ from the activities of cytokines on ß cells, which are mediated by inducible nitric oxide synthase expression and ß-cell production of nitric oxide. These findings provide evidence that the antiviral activities of type I IFN production and apoptosis are elicited in ß cells via the recognition of intracellular viral replication intermediates and that ß cells lack the capacity to respond to extracellular viral intermediates known to activate innate immune responses.

SurfaceGenie: a web-based application for prioritizing cell-type-specific marker candidates.

MOTIVATION: Cell-type-specific surface proteins can be exploited as valuable markers for a range of applications including immunophenotyping live cells, targeted drug delivery and in vivo imaging. Despite their utility and relevance, the unique combination of molecules present at the cell surface are not yet described for most cell types. A significant challenge in analyzing 'omic' discovery datasets is the selection of candidate markers that are most applicable for downstream applications. RESULTS: Here, we developed GenieScore, a prioritization metric that integrates a consensus-based prediction of cell surface localization with user-input data to rank-order candidate cell-type-specific surface markers. In this report, we demonstrate the utility of GenieScore for analyzing human and rodent data from proteomic and transcriptomic experiments in the areas of cancer, stem cell and islet biology. We also demonstrate that permutations of GenieScore, termed IsoGenieScore and OmniGenieScore, can efficiently prioritize co-expressed and intracellular cell-type-specific markers, respectively. AVAILABILITY AND IMPLEMENTATION: Calculation of GenieScores and lookup of SPC scores is made freely accessible via the SurfaceGenie web application: www.cellsurfer.net/surfacegenie. CONTACT: Rebekah.gundry@unmc.edu. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Intraoperative Airway Management Considerations for Adult Patients Presenting With Tracheostomy: A Narrative Review.

Tracheotomy is a surgical procedure through which a tracheostomy, an opening into the trachea, is created. Indications for tracheostomy include facilitation of airway management during prolonged mechanical ventilation, treatment of acute upper airway obstruction when tracheal intubation is unfeasible, management of chronic upper airway obstructive conditions, and planned airway management for major head and neck surgery. Patients who have a recent or long-term tracheostomy may present for a variety of surgical or diagnostic procedures performed under general anesthesia or sedation/analgesia. Airway management of these patients can be challenging and should be planned ahead of time. Anesthesia personnel should be familiar with the different components of cuffed and uncuffed tracheostomy devices and their connectivity to the anesthesia circuits. An appropriate airway management plan should take into account the indication of the tracheostomy, the maturity status of the stoma, the type and size of tracheostomy tube, the expected patient positioning, and presence of patient's concurrent health conditions. Management of the patient with a T-tube is highlighted. Importantly, there is a need for multidisciplinary care involving anesthesiologists, surgical specialists, and perioperative nurses. The aim of this narrative review is to discuss the anesthesia care of patients with a tracheostomy. Key aspects on relevant tracheal anatomy, tracheostomy tubes/devices, alternatives of airway management, and possible complications related to tracheostomy are summarized with a recommendation for an algorithm to manage intraoperative tracheostomy tube dislodgement.

Pancreatic ß-cells detoxify H2O2 through the peroxiredoxin/thioredoxin antioxidant system.

Oxidative stress is thought to promote pancreatic ß-cell dysfunction and contribute to both type 1 and type 2 diabetes. Reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, are mediators of oxidative stress that arise largely from electron leakage during oxidative phosphorylation. Reports that ß-cells express low levels of antioxidant enzymes, including catalase and GSH peroxidases, have supported a model in which ß-cells are ill-equipped to detoxify ROS. This hypothesis seems at odds with the essential role of ß-cells in the control of metabolic homeostasis and organismal survival through exquisite coupling of oxidative phosphorylation, a prominent ROS-producing pathway, to insulin secretion. Using glucose oxidase to deliver H2O2 continuously over time and Amplex Red to measure extracellular H2O2 concentration, we found here that ß-cells can remove micromolar levels of this oxidant. This detoxification pathway utilizes the peroxiredoxin/thioredoxin antioxidant system, as selective chemical inhibition or siRNA-mediated depletion of thioredoxin reductase sensitized ß-cells to continuously generated H2O2 In contrast, when delivered as a bolus, H2O2 induced the DNA damage response, depleted cellular energy stores, and decreased ß-cell viability independently of thioredoxin reductase inhibition. These findings show that ß-cells have the capacity to detoxify micromolar levels of H2O2 through a thioredoxin reductase-dependent mechanism and are not as sensitive to oxidative damage as previously thought.

Peroxiredoxin 1 plays a primary role in protecting pancreatic ß-cells from hydrogen peroxide and peroxynitrite.

Both reactive nitrogen and oxygen species (RNS and ROS), such as nitric oxide, peroxynitrite, and hydrogen peroxide, have been implicated as mediators of pancreatic ß-cell damage during the pathogenesis of autoimmune diabetes. While ß-cells are thought to be vulnerable to oxidative damage due to reportedly low levels of antioxidant enzymes, such as catalase and glutathione peroxidase, we have shown that they use thioredoxin reductase to detoxify hydrogen peroxide. Thioredoxin reductase is an enzyme that participates in the peroxiredoxin antioxidant cycle. Peroxiredoxins are expressed in ß-cells and, when overexpressed, protect against oxidative stress, but the endogenous roles of peroxiredoxins in the protection of ß-cells from oxidative damage are unclear. Here, using either glucose oxidase or menadione to continuously deliver hydrogen peroxide, or the combination of dipropylenetriamine NONOate and menadione to continuously deliver peroxynitrite, we tested the hypothesis that ß-cells use peroxiredoxins to detoxify both of these reactive species. Either pharmacological peroxiredoxin inhibition with conoidin A or specific depletion of cytoplasmic peroxiredoxin 1 (Prdx1) using siRNAs sensitizes INS 832/13 cells and rat islets to DNA damage and death induced by hydrogen peroxide or peroxynitrite. Interestingly, depletion of peroxiredoxin 2 (Prdx2) had no effect. Together, these results suggest that ß-cells use cytoplasmic Prdx1 as a primary defense mechanism against both ROS and RNS.

CCR5 is a required signaling receptor for macrophage expression of inflammatory genes in response to viral double-stranded RNA.

Double-stranded (ds) RNA, both synthetic and produced during virus replication, rapidly stimulates MAPK and NF-κB signaling that results in expression of the inflammatory genes inducible nitric oxide synthase, cyclooxygenase 2, and IL-1ß by macrophages. Using biochemical and genetic approaches, we have identified the chemokine ligand-binding C-C chemokine receptor type 5 (CCR5) as a cell surface signaling receptor required for macrophage expression of inflammatory genes in response to dsRNA. Activation of macrophages by synthetic dsRNA does not require known dsRNA receptors, as poly(inosinic:cytidylic) acid [poly(I:C)] activates signaling pathways leading to expression of inflammatory genes to similar levels in wild-type and Toll-like receptor 3- or melanoma differentiation antigen 5-deficient macrophages. In contrast, macrophage activation in response to poly(I:C) is attenuated in macrophages isolated from mice lacking CCR5. These findings support a role for CCR5 as a cell surface signaling receptor that participates in activation of inflammatory genes in macrophages in response to the viral dsRNA mimetic poly(inosinic:cytidylic) acid by pathways that are distinct from classical dsRNA receptor-mediated responses.

The lung microbiome, vitamin D, and the tuberculous granuloma: A balance triangle.

Mycobacterium tuberculosis (Mtb) has the extraordinary ability to persist for decades within granulomas in the human host. These histopathological structures involved in both protection and pathogenesis, are subject to various influences from the host systemically and through micro-niche environments. Despite the fact that vitamin D (VD) has a key role in macrophage activation and mycobacterial clearance in the early stages of Mtb infection, the overall role of VD in granuloma maintenance or functionality has been scarcely studied. VD deficiency has long time been known to influence on gut microbiota composition, and recent studies have shown that it can also impact on respiratory microbiome. The human microbiota plays an important role in pathogen colonization resistance, and it has been proposed to play a potential role in TB pathogenesis. In this article, we have reviewed current knowledge on the interaction between VD, the lung microbiome and TB, and propose mechanisms by which the tuberculous granuloma's outcome could be modulated by these two factors. The determinants of the final fate of lung granulomas are still unclear, and deciphering the underlying drivers of Mtb infection outcome within those structures is of critical importance.