Recent advances in understanding the physiology of hypoxic sensing by the carotid body [version 1; referees: 2 approved]

Hypoxia resulting from reduced oxygen (O2) levels in the arterial blood is sensed by the carotid body (CB) and triggers reflex stimulation of breathing and blood pressure to maintain homeostasis. Studies in the past five years provided novel insights into the roles of heme oxygenase-2 (HO-2), a carbon monoxide (CO)-producing enzyme, and NADH dehydrogenase Fe-S protein 2, a subunit of the mitochondrial complex I, in hypoxic sensing by the CB. HO-2 is expressed in type I cells, the primary O2-sensing cells of the CB, and binds to O2 with low affinity. O2-dependent CO production from HO-2 mediates hypoxic response of the CB by regulating H2S generation. Mice lacking NDUFS2 show that complex I-generated reactive oxygen species acting on K+ channels confer type I cell response to hypoxia. Whether these signaling pathways operate synergistically or independently remains to be studied

Hypoxia sensing requires H₂S-dependent persulfidation of olfactory receptor 78

Oxygen (O2) sensing by the carotid body is critical for maintaining cardiorespiratory homeostasis during hypoxia. Hydrogen sulfide (H2S) signaling is implicated in carotid body activation by low O2. Here, we show that persulfidation of olfactory receptor 78 (Olfr78) by H2S is an integral component of carotid body activation by hypoxia. Hypoxia and H2S increased persulfidation in carotid body glomus cells and persulfidated cysteine240 in Olfr78 protein in heterologous system. Olfr78 mutants manifest impaired carotid body sensory nerve, glomus cell, and breathing responses to H2S and hypoxia. Glomus cells are positive for GOlf, adenylate cyclase 3 (Adcy3) and cyclic nucleotide–gated channel alpha 2 (Cnga2), key molecules of odorant receptor signaling. Adcy3 or Cnga2 mutants exhibited impaired carotid body and glomus cell responses to H2S and breathing responses to hypoxia. These results suggest that H2S through redox modification of Olfr78 participates in carotid body activation by hypoxia to regulate breathing

A ONE DIMENSIONAL MATHEMATICAL MODEL FOR URODYNAMICS

ABSTRACT Millions of people in the world suffer from urinary incontinence and overactive bladder with the major causes for the symptoms being stress, urge, overflow and functional incontinence. For a more effective treatment of these ailments, a detailed understanding of the urinary flow dynamics is required. This challenging task is not easy to achieve due to the complexity of the problem and the lack of tools to study the underlying mechanisms of the urination process. Theoretical models can help find a better solution for the various disorders of the lower urinary tract, including urinary incontinence, through simulating the interaction between various components involved in the continence mechanism. Using a lumped parameter analysis, a one-dimensional, transient mathematical model was built to simulate a complete cycle of filling and voiding of the bladder. Both the voluntary and involuntary contraction of the bladder walls is modeled along with the transient response of both the internal and external sphincters which dynamically control the urination process. The model also includes the effects signals from the bladder outlet (urethral sphincter, pelvic floor muscles and fascia), the muscles involved in evacuation of the urinary bladder (detrusor muscle) as well as the abdominal wall musculature. The necessary geometrical parameters of the urodynamics model were obtained from the 3D visualization data based on the visible human project. Preliminary results show good agreement with the experimental results found in the literature. The current model could be used as a diagnostic tool for detecting incontinence and simulating possible scenarios for the circumstances leading to incontinence. INTRODUCTION Urinary incontinence has been reported to affect 35% of American women over 50 years of age an almost 15% who have leakage on a daily basi

Chronic Intermittent Hypoxia Alters Local Respiratory Circuit Function at the Level of the preBötzinger Complex

Chronic intermittent hypoxia (CIH) is a common state experienced in several breathing disorders, including obstructive sleep apnea (OSA) and apneas of prematurity. Unraveling how CIH affects the CNS, and in turn how the CNS contributes to apneas is perhaps the most challenging task. The preBötzinger complex (preBötC) is a pre-motor respiratory network critical for inspiratory rhythm generation. Here, we test the hypothesis that CIH increases irregular output from the isolated preBötC, which can be mitigated by antioxidant treatment. Electrophysiological recordings from brainstem slices revealed that CIH enhanced burst-to-burst irregularity in period and/or amplitude. Irregularities represented a change in individual fidelity among preBötC neurons, and changed transmission from preBötC to the hypoglossal motor nucleus (XIIn), which resulted in increased transmission failure to XIIn. CIH increased the degree of lipid peroxidation in the preBötC and treatment with the antioxidant, 5,10,15,20-Tetrakis (1-methylpyridinium-4-yl)-21H,23H-porphyrin manganese(III) pentachloride (MnTMPyP), reduced CIH-mediated irregularities on the network rhythm and improved transmission of preBötC to the XIIn. These findings suggest that CIH promotes a pro-oxidant state that destabilizes rhythmogenesis originating from the preBötC and changes the local rhythm generating circuit which in turn, can lead to intermittent transmission failure to the XIIn. We propose that these CIH-mediated effects represent a part of the central mechanism that may perpetuate apneas and respiratory instability, which are hallmark traits in several dysautonomic conditions

Temporal trends in the incidence of haemophagocytic lymphohistiocytosis: a nationwide cohort study from England 2003-2018

Background Haemophagocytic lymphohistiocytosis (HLH) is rare, results in high mortality and is increasingly being diagnosed. Little is known about what is driving the apparent rise in the incidence of this disease.Methods Using national linked electronic health data from hospital admissions and death certification cases of HLH that were diagnosed in England between 1/1/2003 and 31/12/2018 were identified using a previously validated approach. We calculated incidence rates of diagnosed HLH per million population using mid-year population estimates by calendar year, age group, sex and associated comorbidity (haematological malignancy, inflammatory rheumatological or bowel diseases (IBD)) associated with the diagnosis of HLH. We modelled trends in incidence and the interactions between calendar year, age and associated comorbidity using Poisson regression.Findings There were 1674 people with HLH diagnosed in England between 2003 and 2018. The incidence rate quadrupled (Incidence Rate Ratio (IRR) 2018 compared to 2003: 3.88 95% Confidence Interval (CI) 2.91 to 5.28), increasing 11% annually (adjusted IRR 1.11 95% CI 1.09 to 1.12). There was a rising trend in all age groups except those aged less than 5 years. There was a transition across the age groups with greater increases in those aged 5 to 14 years of HLH associated with rheumatological disease/IBD compared to HLH associated with haematological malignancy, with similar increases in HLH associated with both co-morbidities for those 15-54, and greater increases in associated haematological malignancies for those 55 years and older.Interpretation The incidence of HLH in England has quadrupled between 2003 and 2018, increasing 11% annually. Substantial variation in the incidence occurred by age group and by HLH associated comorbidities with inflammatory rheumatological diseases or IBD associated HLH increasing more among the young and middle age groups, whereas in older age groups the largest increase was seen with haematological malignancy-associated HLH.Evidence before this study There is a paucity of population-based data on the epidemiology of HLH worldwide. The available evidence relies mostly upon a collection of cases series published in The Lancet in 2014 which described 2197 cases of HLH in adults reported in the literature to that point. Almost all of these were from tertiary referral specialist centres and/or described in small case series. The incidence of HLH has only been described in a few reports – and mainly this has focused on children with primary HLH. No previous studies have been large enough to examine trends in incidence by age, sex, underlying risk factors and calendar time.Added value of this study This study quantifies the incidence of diagnosed HLH for the first time in a nationwide manner for all age groups. It reports on 1674 patients with HLH from England and shows that there is substantial variation in the incidence by age group, associated disease and calendar time. The results imply reasons for the increase in HLH could be related to the increasing occurrence of haematological cancer, inflammatory rheumatological or bowel diseases and the treatments given for these conditions. This study has been carried out in partnership with the National Congenital Anomalies and Rare Diseases Registration Service and the methodology described can in future be applied to many rare diseases that as yet lack a way of quantifying crucial epidemiological metrics.Implications of all the available evidence The incidence of HLH is rising rapidly in people older than 5 years of age. This could be due to an increase in the biologic, immunomodulation or immunosuppressive therapy being used in people with haematological cancer and inflammatory rheumatological and bowel diseases. Further work should focus on how to minimise the risk of HLH occurring, or to improve treatment of this often fatal disease among those who need treatment for an associated comorbidity

Programmed Bending Reveals Dynamic Mechanochemical Coupling in Supported Lipid Bilayers

In living cells, mechanochemical coupling represents a dynamic means by which membrane components are spatially organized. An extra-ordinary example of such coupling involves curvature-dependent polar localization of chemically-distinct lipid domains at bacterial poles, which also undergo dramatic reequilibration upon subtle changes in their interfacial environment such as during sporulation. Here, we demonstrate that such interfacially-triggered mechanochemical coupling can be recapitulated in vitro by simultaneous, real-time introduction of mechanically-generated periodic curvatures and attendant strain-induced lateral forces in lipid bilayers supported on elastomeric substrates. In particular, we show that real-time wrinkling of the elastomeric substrate prompts a dynamic domain reorganization within the adhering bilayer, producing large, oriented liquid-ordered domains in regions of low curvature. Our results suggest a mechanism in which interfacial forces generated during surface wrinkling and the topographical deformation of the bilayer combine to facilitate dynamic reequilibration prompting the observed domain reorganization. We anticipate this curvature-generating model system will prove to be a simple and versatile tool for a broad range of studies of curvature-dependent dynamic reorganizations in membranes that are constrained by the interfacial elastic and dynamic frameworks such as the cell wall, glycocalyx, and cytoskeleton

Double-stranded RNA-activated protein kinase PKR of fishes and amphibians: Varying the number of double-stranded RNA binding domains and lineage-specific duplications

BackgroundDouble-stranded (ds) RNA, generated during viral infection, binds and activates the mammalian anti-viral protein kinase PKR, which phosphorylates the translation initiation factor eIF2alpha leading to the general inhibition of protein synthesis. Although PKR-like activity has been described in fish cells, the responsible enzymes eluded molecular characterization until the recent discovery of goldfish and zebrafish PKZ, which contain Z-DNA-binding domains instead of dsRNA-binding domains (dsRBDs). Fish and amphibian PKR genes have not been described so far.ResultsHere we report the cloning and identification of 13 PKR genes from 8 teleost fish and amphibian species, including zebrafish, demonstrating the coexistence of PKR and PKZ in this latter species. Analyses of their genomic organization revealed up to three tandemly arrayed PKR genes, which are arranged in head-to-tail orientation. At least five duplications occurred independently in fish and amphibian lineages. Phylogenetic analyses reveal that the kinase domains of fish PKR genes are more closely related to those of fish PKZ than to the PKR kinase domains of other vertebrate species. The duplication leading to fish PKR and PKZ genes occurred early during teleost fish evolution after the divergence of the tetrapod lineage. While two dsRBDs are found in mammalian and amphibian PKR, one, two or three dsRBDs are present in fish PKR. In zebrafish, both PKR and PKZ were strongly upregulated after immunostimulation with some tissue-specific expression differences. Using genetic and biochemical assays we demonstrate that both zebrafish PKR and PKZ can phosphorylate eIF2alpha in yeast.ConclusionConsidering the important role for PKR in host defense against viruses, the independent duplication and fixation of PKR genes in different lineages probably provided selective advantages by leading to the recognition of an extended spectrum of viral nucleic acid structures, including both dsRNA and Z-DNA/RNA, and perhaps by altering sensitivity to viral PKR inhibitors. Further implications of our findings for the evolution of the PKR family and for studying PKR/PKZ interactions with viral gene products and their roles in viral infections are discussed

25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 exert distinct effects on human skeletal muscle function and gene expression

Age-associated decline in muscle function represents a significant public health burden. Vitamin D-deficiency is also prevalent in aging subjects, and has been linked to loss of muscle mass and strength (sarcopenia), but the precise role of specific vitamin D metabolites in determining muscle phenotype and function is still unclear. To address this we quantified serum concentrations of multiple vitamin D metabolites, and assessed the impact of these metabolites on body composition/muscle function parameters, and muscle biopsy gene expression in a retrospective study of a cohort of healthy volunteers. Active serum 1,25-dihydroxyvitamin D3 (1α,25(OH)2D3), but not inactive 25-hydroxyvitamin D3 (25OHD3), correlated positively with measures of lower limb strength including power (rho = 0.42, p = 0.02), velocity (Vmax, rho = 0.40, p = 0.02) and jump height (rho = 0.36, p = 0.04). Lean mass correlated positively with 1α,25(OH)2D3 (rho = 0.47, p = 0.02), in women. Serum 25OHD3 and inactive 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) had an inverse relationship with body fat (rho = -0.30, p = 0.02 and rho = -0.33, p = 0.01, respectively). Serum 25OHD3 and 24,25(OH)2D3 were also correlated with urinary steroid metabolites, suggesting a link with glucocorticoid metabolism. PCR array analysis of 92 muscle genes identified vitamin D receptor (VDR) mRNA in all muscle biopsies, with this expression being negatively correlated with serum 25OHD3, and Vmax, and positively correlated with fat mass. Of the other 91 muscle genes analysed by PCR array, 24 were positively correlated with 25OHD3, but only 4 were correlated with active 1α,25(OH)2D3. These data show that although 25OHD3 has potent actions on muscle gene expression, the circulating concentrations of this metabolite are more closely linked to body fat mass, suggesting that 25OHD3 can influence muscle function via indirect effects on adipose tissue. By contrast, serum 1α,25(OH)2D3 has limited effects on muscle gene expression, but is associated with increased muscle strength and lean mass in women. These pleiotropic effects of the vitamin D ‘metabolome’ on muscle function indicate that future supplementation studies should not be restricted to conventional analysis of the major circulating form of vitamin D, 25OHD3

Deficiency of Pkc1 activity affects glycerol metabolism in Saccharomyces cerevisiae

In pressProtein kinase C is apparently involved in the control of many cellular systems: the cell wall integrity pathway, the synthesis of ribosomes, the appropriated reallocation of transcription factors under specific stress conditions and also the regulation of N-glycosylation activity. All these observations suggest the existence of additional targets not yet identified. In the context of the control of carbon metabolism, previous data demonstrated that Pkc1 p might play a central role in the control of cellular growth and metabolism in yeast. In particular, it has been suggested that it might be involved in the derepression of genes under glucose-repression by driving an appropriated subcellular localization of transcriptional factors, such as Mig1 p. In this work, we show that pkc1∆ mutant is unable to grow on glycerol because it cannot perform the derepression of GUT1 gene that encodes for glycerol kinase. Additionally, active transport is also partially affected. Using this phenotype, we were able to isolate a new pkc1∆ revertant. We also isolated two transformants identified as the nuclear exportin Msn5 and the histone deacetylase Hos2 extragenic suppressors of this mutation. Based on these results, we postulate that Pkc1 p may be involved in the control of the cellular localization and/or regulation of the activity of nuclear proteins implicated in gene expression.Fundação Universidade Federal de Ouro Preto (FUFOP). Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) - CBS-1875/95. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) - 300998/89-9 to R.L.B., 301255/01-6 to L.G.F