PEPITEM modulates leukocyte trafficking to reduce obesity-induced inflammation

Dysregulation of leukocyte trafficking, lipid metabolism, and other metabolic processes are the hallmarks that underpin and drive pathology in obesity. Current clinical management targets alternations in lifestyle choices (e.g. exercise, weight loss) to limit the impact of the disease. Crucially, re-gaining control over the pathogenic cellular and molecular processes may offer an alternative, complementary strategy for obese patients. Here we investigate the impact of the immunopeptide, PEPITEM, on pancreas homeostasis and leukocyte trafficking in mice on high-fed obesogenic diet (HFD). Both prophylactic and therapeutic treatment with PEPITEM alleviated the effects of HFD on the pancreas, reducing pancreatic beta cell size. Moreover, PEPITEM treatment also limited T-cell trafficking (CD4+ T-cells and KLRG1+ CD3+ T-cells) to obese visceral, but not subcutaneous, adipose tissue. Similarly, PEPITEM treatment reduced macrophage numbers within the peritoneal cavity of mice on HFD diet at both 6 and 12 weeks. By contrast, PEPITEM therapy elevated numbers of T and B cells were observed in the secondary lymphoid tissues (e.g. spleen and inguinal lymph node) when compared to the untreated HFD controls. Collectively our data highlights the potential for PEPITEM as a novel therapy to combat the systemic low-grade inflammation experienced in obesity and minimize the impact of obesity on pancreatic homeostasis. Thus, offering an alternative strategy to reduce the risk of developing obesity-related co-morbidities, such as type 2 diabetes mellitus, in individuals at high risk and struggling to control their weight through lifestyle modifications.

GC-Globulin/Vitamin D-Binding Protein Is Required for Pancreatic α-Cell Adaptation to Metabolic Stress

GC-globulin (GC), or vitamin D-binding protein, is a multifunctional protein involved in the transport of circulating vitamin 25(OH)D and fatty acids, as well as actin scavenging. In the pancreatic islets, the gene encoding GC, GC/Gc, is highly localized to glucagon-secreting α-cells. Despite this, the role of GC in α-cell function is poorly understood. We previously showed that GC is essential for α-cell morphology, electrical activity, and glucagon secretion. We now show that loss of GC exacerbates α-cell failure during metabolic stress. High-fat diet-fed GC-/- mice have basal hyperglucagonemia, which is associated with decreased α-cell size, impaired glucagon secretion and Ca2+ fluxes, and changes in glucose-dependent F-actin remodelling. Impairments in glucagon secretion can be rescued using exogenous GC to replenish α-cell GC levels, increase glucagon granule area, and restore the F-actin cytoskeleton. Lastly, GC levels decrease in α-cells of donors with type 2 diabetes, which is associated with changes in α-cell mass, morphology, and glucagon expression. Together, these data demonstrate an important role for GC in α-cell adaptation to metabolic stress.

Treatment of congenital thrombocytopenia and decreased collagen reactivity in G6b-B-deficient mice

Mice lacking the immunoreceptor tyrosine-based inhibition motif-containing co-inhibitory receptor G6b-B (Mpig6b, G6b knockout, KO) are born with a complex megakaryocyte (MK) per platelet phenotype, characterized by severe macrothrombocytopenia, expansion of the MK population, and focal myelofibrosis in the bone marrow and spleen. Platelets are almost completely devoid of the glycoprotein VI (GPVI)-FcRγ-chain collagen receptor complex, have reduced collagen integrin α2β1, elevated Syk tyrosine kinase activity, and a subset has increased surface immunoglobulins. A similar phenotype was recently reported in patients with null and loss-of-function mutations in MPIG6B. To better understand the cause and treatment of this pathology, we used pharmacological- and genetic-based approaches to rescue platelet counts and function in G6b KO mice. Intravenous immunoglobulin resulted in a transient partial recovery of platelet counts, whereas immune deficiency did not affect platelet counts or receptor expression in G6b KO mice. Syk loss-of-function (R41A) rescued macrothrombocytopenia, GPVI and α2β1 expression in G6b KO mice, whereas treatment with the Syk kinase inhibitor BI1002494 partially rescued platelet count but had no effect on GPVI and α2β1 expression or bleeding. The Src family kinase inhibitor dasatinib was not beneficial in G6b KO mice. In contrast, treatment with the thrombopoietin mimetic romiplostim rescued thrombocytopenia, GPVI expression, and platelet reactivity to collagen, suggesting that it may be a promising therapeutic option for patients lacking functional G6b-B. Intriguingly, GPVI and α2β1 expression were significantly downregulated in romiplostim-treated wild-type mice, whereas GPVI was upregulated in romiplostim-treated G6b KO mice, suggesting a cell intrinsic feedback mechanism that autoregulates platelet reactivity depending on physiological needs.

Sex-specific effects of CD248 on metabolism and the adipose tissue lipidome

Cd248 has recently been associated with adipose tissue physiology, demonstrated by reduced weight gain in high fat diet-fed mice with genetic deletion of Cd248 relative to controls. Here we set out to determine the metabolic consequences of loss of Cd248. Strikingly, we find these to be sex specific; By subjecting Cd248-/- and Cd248+/+ mice to a high fat diet and indirect calorimetry study, we identified that only male Cd248-/- mice show reduced weight gain compared to littermate control wildtype mice. In addition, male (but not female) mice showed a lower respiratory exchange ratio on both chow and high fat diets, indicating a predisposition to metabolise lipid. Lipidomic studies on specific fat depots found reduced triglyceride and diglyceride deposition in male Cd248-/- mice, and this was supported by reduced expression of lipogenic and adipogenic genes. Finally, metabolomic analysis of isolated, differentiated preadipocytes found alterations in metabolic pathways associated with lipid deposition in cells isolated from male, but not female, Cd248-/- mice. Overall, our results highlight the importance of sex controls in animal studies and point to a role for Cd248 in sex- and depot-specific regulation of lipid metabolism.

ODP443 Targeting NAD+ availability modulates 11β- Hydroxysteroid dehydrogenase 1 activity in mouse and human cell lines and primary cells

Four nicotinamide adenine dinucleotide coenzymes – NAD+, NADH, NADP+, and NADPH – are the central catalysts of metabolism. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is NADPH-dependent reductase that catalyses the reduction of the inactive glucocorticoid cortisone) to active cortisol (11-dehydrocorticosterone to corticosterone in rodents). 11β-HSD1 is in the endoplasmic reticulum (ER) lumen, and the level of NADPH in the ER regulates enzyme activity. Little is known about the biochemical mechanisms controlling cytosolic/ER NAD(P)(H) crosstalk. Here we examined how perturbed cellular NAD+ availability modulates 11β-HSD1 enzyme activity in the ER across a range of mouse and human cell types. 11β-HSD1 activity was measured in a series of transformed and primary mouse and human liver (HepG2), muscle, and Human Dermal Fibroblast cells (HDFn) depleted for NAD+ using FK866 to inhibit nicotinamide phosphoribosyl transferase (NAMPT), the rate-limiting enzyme in NAD+ biosynthesis. To replete NAD+ we supplemented cells with 0.5mM of NAD+ precursors nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). FK866 (100nM, 48h) was effective at depleting NAD+ by approximately 90% in C2C12 myotubes and 50% in HepG2 liver cells. In each cell line, 11β-HSD1 reductase activity was decreased by FK866 compared to untreated controls (80% in C2C12 P<0. 0001, 55% in HepG2, P=0. 03 and 65% in HDFn P=0. 002). Restoring NAD+ level with NR (0.5mM, 6h) in C2C12 and (0.5mM, 24h) in HepG2 and HDFn rescued 11β-HSD1 enzyme activity compared with no precursor treatment (60% in C2C12 P=0. 0007, 52% in HepG2 P=0. 03 and 68% in HDFn P=0. 0006). Human dermal fibroblasts treated with TNFa (10nM, 24h) boosted 11β-HSD1 expression 4-fold, however this was not able to overcome the FK866 induced drop-in reductase activity. These data show that depletion of NAD+ and impaired 11β-HSD1 reductase activity in the ER is a generalised phenomenon across cell types. This suggests a crosstalk between cytosolic and ER NAD(P)(H) pools that can respond rapidly to changes in NAD+ precursor availability. This could provide new insight into the regulation of cellular glucocorticoid metabolism and ER NAD(P)(H) homeostasis.

Presentation: No date and time listed

RF33 | PSAT92 Glucocorticoid Excess Alters Metabolic Rate in Male and Female C57BL/6J Mice

Introduction

Glucocorticoids are vital for regulating metabolic processes, as well as use in medical treatments. However glucocorticoid excess is known to cause negative metabolic effects including hyperglycaemia, muscle atrophy and fat accumulation, ultimately leading to Cushing's Syndrome. The effect on energy metabolism and metabolic rate remains undefined and merits investigation in both male and female mice.

Methods

24 male and 24 female C57BL/6J mice were randomly assigned to a corticosterone (100mg/L, approximately 300µg/day) or a vehicle control group. Mice were treated ad libitum via drinking water for 3 weeks, whilst being fed a standard chow diet. Mice were placed into a TSE Phenomaster system for the final week of treatment for indirect calorimetry assessment.

Results

Corticosterone treatment resulted in a typical phenotype of glucocorticoid excess, however female mice experienced significantly greater fat accumulation and bodyweight gain compared to males. Females treated with corticosterone exhibited increased energy expenditure (EE, 25±5.9%), oxygen consumption (21.7±10.0%) and carbon dioxide production (36.4±14.3%) during the day compared to controls, but males did not. However, corticosterone did significantly elevate the respiratory exchange ratio (RER) towards 1 in both males (10.7±5.7%) and females (11.8±7.0%) during the day. At night, when mice are naturally more active and EE increases, female corticosterone mice no longer had elevated EE, oxygen consumption and carbon dioxide production compared to controls. However, RER remained elevated in females (7.6%±4.8%) and moderately so in males (3.2±2.6%), staying close to or exceeding 1 in both. Corticosterone treated mice were hyperphagic and polydipsic throughout, eating and drinking significantly more than controls during both night and day, with intake peaking at night. Subsequent metabolomic analysis of tissue samples (skeletal muscle, liver, gonadal fat) revealed significant treatment and sex differences.

Conclusion

and further investigation: These findings provide further insights into the metabolic consequences of glucocorticoid excess in male and female mice. Whilst energy metabolism and metabolic rate are altered in both (especially during the day), the metabolic effects of glucocorticoid excess might be exaggerated in females. Further investigation will determine whether these changes are driven simply by increased animal activity, increased feeding and drinking or another mechanism. Additionally, we will determine whether 11β-HSD1 KO prevents these changes, as it does with other negative metabolic effects associated with glucocorticoid excess.

Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 1:06 p.m. - 1:11 p.m.

Nicotinamide riboside has minimal impact on energy metabolism in mouse models of mild obesity

Supplementation with precursors of NAD has been shown to prevent and reverse insulin resistance, mitochondrial dysfunction, and liver damage in mouse models of diet-induced obesity. We asked whether the beneficial effects of supplementation with the NAD precursor nicotinamide riboside (NR) are dependent on mouse strain. We compared the effects of NR supplementation on whole-body energy metabolism and mitochondrial function in mildly obese C57BL/6N and C57BL/6J mice, two commonly used strains to investigate metabolism. Male C57BL/6N and C57BL/6J mice were fed a high-fat diet (HFD) or standard chow with or without NR supplementation for 8 weeks. Body and organ weights, glucose tolerance, and metabolic parameters as well as mitochondrial O2 flux in liver and muscle fibers were assessed. We found that NR supplementation had no influence on body or organ weight, glucose metabolism or hepatic lipid accumulation, energy expenditure, or metabolic flexibility but increased mitochondrial respiration in soleus muscle in both mouse strains. Strain-dependent differences were detected for body and fat depot weight, fasting blood glucose, hepatic lipid accumulation, and energy expenditure. We conclude that, in mild obesity, NR supplementation does not alter metabolic phenotype in two commonly used laboratory mouse strains.

Vitamin-D-Binding Protein Contributes to the Maintenance of α Cell Function and Glucagon Secretion

Vitamin-D-binding protein (DBP) or group-specific component of serum (GC-globulin) carries vitamin D metabolites from the circulation to target tissues. DBP is highly localized to the liver and pancreatic α cells. Although DBP serum levels, gene polymorphisms, and autoantigens have all been associated with diabetes risk, the underlying mechanisms remain unknown. Here, we show that DBP regulates α cell morphology, α cell function, and glucagon secretion. Deletion of DBP leads to smaller and hyperplastic α cells, altered Na+ channel conductance, impaired α cell activation by low glucose, and reduced rates of glucagon secretion both in vivo and in vitro. Mechanistically, this involves reversible changes in islet microfilament abundance and density, as well as changes in glucagon granule distribution. Defects are also seen in β cell and δ cell function. Immunostaining of human pancreata reveals generalized loss of DBP expression as a feature of late-onset and long-standing, but not early-onset, type 1 diabetes. Thus, DBP regulates α cell phenotype, with implications for diabetes pathogenesis.

Induction of the nicotinamide riboside kinase NAD+ salvage pathway in a model of sarcoplasmic reticulum dysfunction

Background

Hexose-6-Phosphate Dehydrogenase (H6PD) is a generator of NADPH in the Endoplasmic/Sarcoplasmic Reticulum (ER/SR). Interaction of H6PD with 11β-hydroxysteroid dehydrogenase type 1 provides NADPH to support oxo-reduction of inactive to active glucocorticoids, but the wider understanding of H6PD in ER/SR NAD(P)(H) homeostasis is incomplete. Lack of H6PD results in a deteriorating skeletal myopathy, altered glucose homeostasis, ER stress and activation of the unfolded protein response. Here we further assess muscle responses to H6PD deficiency to delineate pathways that may underpin myopathy and link SR redox status to muscle wide metabolic adaptation.

Methods

We analysed skeletal muscle from H6PD knockout (H6PDKO), H6PD and NRK2 double knockout (DKO) and wild-type (WT) mice. H6PDKO mice were supplemented with the NAD⁺ precursor nicotinamide riboside. Skeletal muscle samples were subjected to biochemical analysis including NAD(H) measurement, LC-MS based metabolomics, Western blotting, and high resolution mitochondrial respirometry. Genetic and supplement models were assessed for degree of myopathy compared to H6PDKO.

Results

H6PDKO skeletal muscle showed adaptations in the routes regulating nicotinamide and NAD⁺ biosynthesis, with significant activation of the Nicotinamide Riboside Kinase 2 (NRK2) pathway. Associated with changes in NAD⁺ biosynthesis, H6PDKO muscle had impaired mitochondrial respiratory capacity with altered mitochondrial acylcarnitine and acetyl-CoA metabolism. Boosting NAD⁺ levels through the NRK2 pathway using the precursor nicotinamide riboside elevated NAD⁺/NADH but had no effect to mitigate ER stress and dysfunctional mitochondrial respiratory capacity or acetyl-CoA metabolism. Similarly, H6PDKO/NRK2 double KO mice did not display an exaggerated timing or severity of myopathy or overt change in mitochondrial metabolism despite depression of NAD⁺ availability.

Conclusions

These findings suggest a complex metabolic response to changes in muscle SR NADP(H) redox status that result in impaired mitochondrial energy metabolism and activation of cellular NAD⁺ salvage pathways. It is possible that SR can sense and signal perturbation in NAD(P)(H) that cannot be rectified in the absence of H6PD. Whether NRK2 pathway activation is a direct response to changes in SR NAD(P)(H) availability or adaptation to deficits in metabolic energy availability remains to be resolved.

The Gp1ba-Cre transgenic mouse: a new model to delineate platelet and leukocyte functions

Conditional knockout (KO) mouse models are invaluable for elucidating the physiological roles of platelets. The Platelet factor 4-Cre recombinase (Pf4-Cre) transgenic mouse is the current model of choice for generating megakaryocyte/platelet-specific KO mice. Platelets and leukocytes work closely together in a wide range of disease settings, yet the specific contribution of platelets to these processes remains unclear. This is partially a result of the Pf4-Cre transgene being expressed in a variety of leukocyte populations. To overcome this issue, we developed a Gp1ba-Cre transgenic mouse strain in which Cre expression is driven by the endogenous Gp1ba locus. By crossing Gp1ba-Cre and Pf4-Cre mice to the mT/mG dual-fluorescence reporter mouse and performing a head-to-head comparison, we demonstrate more stringent megakaryocyte lineage-specific expression of the Gp1ba-Cre transgene. Broader tissue expression was observed with the Pf4-Cre transgene, leading to recombination in many hematopoietic lineages, including monocytes, macrophages, granulocytes, and dendritic and B and T cells. Direct comparison of phenotypes of Csk, Shp1, or CD148 conditional KO mice generated using either the Gp1ba-Cre or Pf4-Cre strains revealed similar platelet phenotypes. However, additional inflammatory and immunological anomalies were observed in Pf4-Cre-generated KO mice as a result of nonspecific deletion in other hematopoietic lineages. By excluding leukocyte contributions to phenotypes, the Gp1ba-Cre mouse will advance our understanding of the role of platelets in inflammation and other pathophysiological processes in which platelet-leukocyte interactions are involved.

Abstract 55: Romiplostim Treatment Restores GPVI Expression and Platelet Counts in Mice Lacking the ITIM-Containing Receptor G6b-B

We recently demonstrated that the immunoreceptor tyrosine-based inhibition motif (ITIM)-containing receptor G6b-B plays a critical role in regulating platelet homeostasis. Mice lacking G6b-B exhibit a complex phenotype that includes severe macrothrombocytopenia, platelet surface immunoglobulins, reduced expression of the collagen activation receptor GPVI, and aberrant platelet function. In this study, we tested the effects of the thrombopoietin-mimetic romiplostim in ameliorating defects seen in G6b-B-deficient mice. Subcutaneous administration of romiplostim (100 μg/kg romiplostim every three days) restored platelet counts to normal levels in G6b-B-deficient mice within two weeks. Platelet surface GPVI expression was also elevated by five-fold in romiplostim-treated G6b-B-deficient mice compared with platelets from mice treated with vehicle alone, restoring platelet reactivity to the GPVI-specific agonist collagen-related peptide (CRP). In contrast, the same romiplostim regimen induced a 40% reduction in platelet surface GPVI expression in control mice, resulting in comparable levels of GPVI in romiplostim-treated G6b-B-deficient and control mice. Megakaryocyte counts were dramatically increased in the bone marrow and spleen of romiplostim-treated G6b-B-deficient and control mice, accompanied by severe myelofibrosis in both genetic backgrounds. Bone marrow-derived megakaryocytes from G6b-B-deficient mice grew normally in vitro in the presence of thrombopoietin, but exhibited reduced proplatelet formation on a fibrinogen-coated surface. Findings from this study demonstrate that romiplostim can be used to restore GPVI expression in addition to platelet counts in G6b-B-deficient mice, but has severe side-effects on bone marrow and spleen myelofibrosis. This approach can now be applied to further investigate the functional role of G6b-B in regulating platelet counts and reactivity.

This work was funded by the British Heart Foundation.

Dominant Role of the Protein-Tyrosine Phosphatase CD148 in Regulating Platelet Activation Relative to Protein-Tyrosine Phosphatase-1B

Objective—

The receptor-like protein-tyrosine phosphatase (PTP) CD148 and the nontransmembrane PTP1-B have been shown to be net positive regulators of Src family kinases in platelets. In the present study, we compared the relative contributions of these PTPs in platelet activation by the major glycoprotein, glycoprotein VI, α IIb β 3 , and C-type lectin-like receptor 2 (CLEC-2).

Methods and Results—

PTP-1B–deficient mouse platelets responded normally to the glycoprotein VI–specific agonist collagen-related peptide and antibody-mediated CLEC-2 activation. However, they exhibited a marginal reduction in α IIb β 3 -mediated Src family kinase activation and tyrosine phosphorylation. In contrast, CD148-deficient platelets exhibited a dramatic reduction in activation by glycoprotein VI and α IIb β 3 and a marginal reduction in response to activation by CLEC-2, which was further enhanced in the absence of PTP-1B. These defects were associated with reduced activation of Src family kinase and spleen tyrosine kinase, suggesting a causal relationship. Under arteriolar flow conditions, there was defective aggregate formation in the absence of PTP-1B and, to a greater extent, CD148 and a severe abrogation of both adhesion and aggregation in the absence of both PTPs.

Conclusion—

Findings from this study demonstrate that CD148 plays a dominant role in activating Src family kinases in platelets relative to PTP-1B. Both PTPs are required for optimal platelet activation and aggregate formation under high arterial shear rates.

Mice lacking the ITIM-containing receptor G6b-B exhibit macrothrombocytopenia and aberrant platelet function

Platelets are highly reactive cell fragments that adhere to exposed extracellular matrix (ECM) and prevent excessive blood loss by forming clots. Paradoxically, megakaryocytes, which produce platelets in the bone marrow, remain relatively refractory to the ECM-rich environment of the bone marrow despite having the same repertoire of receptors as platelets. These include the ITAM (immunoreceptor tyrosine-based activation motif)-containing collagen receptor complex, which consists of glycoprotein VI (GPVI) and the Fc receptor γ-chain, and the ITIM (immunoreceptor tyrosine-based inhibition motif)-containing receptor G6b-B. We showed that mice lacking G6b-B exhibited macrothrombocytopenia (reduced platelet numbers and the presence of enlarged platelets) and a susceptibility to bleeding as a result of aberrant platelet production and function. Platelet numbers were markedly reduced in G6b-B-deficient mice compared to those in wild-type mice because of increased platelet turnover. Furthermore, megakaryocytes in G6b-B-deficient mice showed enhanced metalloproteinase production, which led to increased shedding of cell-surface receptors, including GPVI and GPIbα. In addition, G6b-B-deficient megakaryocytes exhibited reduced integrin-mediated functions and defective formation of proplatelets, the long filamentous projections from which platelets bud off. Together, these findings establish G6b-B as a major inhibitory receptor regulating megakaryocyte activation, function, and platelet production.

Efficacy and safety of silver textile in the treatment of atopic dermatitis (AD)

BACKGROUND

Patients with atopic dermatitis (AD) have an increased tendency to develop bacterial skin infections. Colonization with Staphylococcus aureus is known to be a major trigger and might also play a pathophysiological role. Because of their antiseptic action, silver-coated textiles suppress S. aureus colonization and toxin formation, thus damping the inflammatory reaction.

OBJECTIVES

To evaluate the clinical effectiveness and safety of a special silver textile in the treatment of patients suffering from acute AD.

METHODS

In a randomized phase II monocenter parallel-group comparative study 30 patients were recruited (average age 25.5 years, min. 4 years, max. 70 years) who were affected by AD in an acute phase. During the first study phase from Day 1 to Day 14, 10 patients received a silver textile (Group 1), 10 a silver-free textile (Group 2), and 10 prednicarbate ointment (Group 3). In the second phase from Day 15 to Day 28 all patients wore the silver textile, and during the follow-up period from Day 28 to Day 56 no textiles were used. Prednicarbate ointment was allowed as emergency medication, but ointment consumption was measured. The overall severity of the disease was evaluated using the SCORAD index as the primary efficacy parameter. Secondary parameters included severity of pruritus and the patients' assessment of their disease control (uncontrolled, limited, good or complete). Safety tests included hematology, blood chemistry, urinalysis for silver, and physical examination for silver deposits in the skin and mucous membranes.

RESULTS

The initial SCORAD was 61.6 (IQR 26.6, min. 30.6, max. 99.9). At the end of the Study Phase 1 the SCORAD had improved significantly in the patients of Groups 1 (74.6-29.9, p = 0.005) and 3 (57.8-24.0, p = 0.009). During Study Phase 2 healing of eczema continued in Group 1 (SCORAD 29.9-18.1, p = 0.037), was observed in Group 2 (48.2-24.1, p = 0.015), and remained at an improved level in Group 3 (SCORAD 24-23.5). Consumption of prednicarbate ointment (Phase 1, Phase 2, follow-up period, medians are given): Group 1: 135 g, 10 g, 45 g; Group 2: 13 g, 0 g, 0 g; Group 3: 145 g, 30 g, 90 g. Silver textiles reduced the severity of the pruritus (p = 0.031); silver-free textiles (n.s.) and prednicarbate (n.s.) were less effective. No undesired events were observed.

CONCLUSION

The elastic silver textile worn directly against the skin led to an impressive improvement of AD and a reduction in the use of prednicarbate ointment.

Chlorobium ferrooxidans sp. nov., a phototrophic green sulfur bacterium that oxidizes ferrous iron in coculture with a "Geospirillum" sp. strain

A green phototrophic bacterium was enriched with ferrous iron as sole electron donor and was isolated in defined coculture with a spirilloid chemoheterotrophic bacterium. The coculture oxidized ferrous iron to ferric iron with stoichiometric formation of cell mass from carbon dioxide. Sulfide, thiosulfate, or elemental sulfur was not used as electron donor in the light. Hydrogen or acetate in the presence of ferrous iron increased the cell yield of the phototrophic partner, and hydrogen could also be used as sole electron source. Complexed ferric iron was slowly reduced to ferrous iron in the dark, with hydrogen as electron source. Similar to Chlorobium limicola, the phototrophic bacterium contained bacteriochlorophyll c and chlorobactene as photosynthetic pigments, and also resembled representatives of this species morphologically. On the basis of 16S rRNA sequence comparisons, this organism clusters with Chlorobium, Prosthecochloris, and Pelodictyon species within the green sulfur bacteria phylum. Since the phototrophic partner in the coculture KoFox is only moderately related to the other members of the cluster, it is proposed as a new species, Chlorobium ferrooxidans. The chemoheterotrophic partner bacterium, strain KoFum, was isolated in pure culture with fumarate as sole substrate. The strain was identified as a member of the epsilon-subclass of the Proteobacteria closely related to "Geospirillum arsenophilum" on the basis of physiological properties and 16S rRNA sequence comparison. The "Geospirillum" strain was present in the coculture only in low numbers. It fermented fumarate, aspartate, malate, or pyruvate to acetate, succinate, and carbon dioxide, and could reduce nitrate to dinitrogen gas. It was not involved in ferrous iron oxidation but possibly provided a thus far unidentified growth factor to the phototrophic partner.

Mutual interference of myotonia and muscular dystrophy in the mouse: a study on ADR-MDX double mutants

For Duchenne muscular dystrophy (DMD, dystrophin deficiency) and Thomsen/Becker myotonia (muscular chloride channel deficiency) genetically homologous mouse models are available, the dystrophin-deficient MDX mouse and the myotonic ADR mouse. Whereas the latter shows more severe symptoms than human myotonia patients, the MDX mouse, in contrast to DMD patients, is only mildly affected. We have introduced, by appropriate breeding, the defect leading to myotonia (Clc1 null mutation, adr allele) into MDX mice, thus creating ADR-MDX double mutants. The expectation was that, due to mechanical stress during myotonic cramps, the ADR status should symptomatically aggravate the muscle fibre necrosis caused by the dystrophin deficiency. The overall symptoms of the double mutants were dominated by myotonia. Weight reduction and premature death rate were higher in ADR-MDX than in ADR mice. Sarcolemmal ruptures as indicated by influx into muscle fibres of serum globulins and injected Evans blue were found with great inter-individual variation in MDX and in ADR-MDX muscles. Affected fibres were found mainly in large groups in MDX but single or in small clusters in ADR-MDX leg muscles. The symptoms of myotonia (aftercontractions, shift towards oxidative fibres) were less pronounced in ADR-MDX than in ADR muscles. Conversely, numbers of damaged fibres as well as the percentage of central nuclei (an indicator of fibre regeneration) were significantly lower in ADR-MDX than in MDX skeletal muscles. Thus it appears that, at the level of the muscle fibre, myotonia and muscular dystrophy attenuate each other.

Phototrophic oxidation of ferrous iron by a Rhodomicrobium vannielii strain

Oxidation of ferrous iron was studied with the anaerobic phototrophic bacterial strain BS-1. Based on morphology, substrate utilization patterns, arrangement of intracytoplasmic membranes and the in vivo absorption spectrum, this strain was assigned to the known species Rhodomicrobium vannielii. Also, the type strain of this species oxidized ferrous iron in the light. Phototrophic growth of strain BS-1 with ferrous iron as electron donor was stimulated by the presence of acetate or succinate as cosubstrates. The ferric iron hydroxides produced precipitated on the cell surfaces as solid crusts which impeded further iron oxidation after two to three generations. The complexing agent nitrilotriacetate stimulated iron oxidation but the yield of cell mass did not increase stoichiometrically under these conditions. Other complexing agents inhibited cell growth. Ferric iron was not reduced in the dark, and manganese salts were neither oxidized nor reduced. It is concluded that ferrous iron oxidation by strain BS-1 is only a side activity of this bacterium that cannot support growth exclusively with this electron source over prolonged periods of time.

Complete assimilation of cysteine by a newly isolated non-sulfur purple bacterium resembling Rhodovulum sulfidophilum (Rhodobacter sulfidophilus)

A rod-shaped, motile, phototrophic bacterium, strain SiCys, was enriched and isolated from a marine microbial mat, with cysteine as sole substrate. During phototrophic anaerobic growth with cysteine, sulfide was produced as an intermediate, which was subsequently oxidized to sulfate. The molar growth yield with cysteine was 103 g mol-1, in accordance with complete assimilation of electrons from the carbon and the sulfur moiety into cell material. Growth yields with alanine and serine were proportionally lower. Thiosulfate, sulfide, hydrogen, and several organic compounds were used as electron donors in the light, whereas cystine, sulfite, or elemental sulfur did not support phototrophic anaerobic growth. Aerobic growth in the dark was possible with fructose as substrate. Cultures of strain SiCys were yellowish-brown in color and contained bacteriochlorophyll a, spheroidene, spheroidenone, and OH-spheroidene as major photosynthetic pigments. Taking the morphology, photosynthetic pigments, aerobic growth in the dark, and utilization of sulfide for phototrophic growth into account, strain SiCys was assigned to the genus Rhodovulum (formerly Rhodobacter) and tentatively classified as a strain of R. sulfidophilum. In cell-free extracts in the presence of pyridoxal phosphate, cysteine was converted to pyruvate and sulfide, which is characteristic for cysteine desulfhydrase activity (l-cystathionine gamma-lyase, EC 4.4. 1.1).

Anaerobic degradation of 3-hydroxybenzoate by a newly isolated nitrate-reducing bacterium

A Gram-negative nitrate-reducing bacterium, strain Asl-3, was isolated from activated sludge with nitrate and 3-hydroxybenzoate as sole source of carbon and energy. The new isolate was facultatively anaerobic, catalase- and oxidase-positive and polarly monotrichously flagellated. In addition to nitrate, nitrite, N2O, and O2 served as electron acceptors. Growth with 3-hydroxybenzoate and nitrate was biphasic: nitrate was completely reduced to nitrite before nitrite reduction to N2 started. Benzoate, 3-hydroxybenzoate, 4-hydroxybenzoate, protocatechuate or phenyl-acetate served as electron and carbon source under aerobic and anaerobic conditions. During growth with excess carbon source, poly-beta-hydroxybutyrate was formed. These characteristics allow the affiliation of strain Asl-3 with the family Pseudomonadaceae. Analogous to the pathway of 4-hydroxybenzoate degradation in other bacteria, the initial step in anaerobic 3-hydroxybenzoate degradation by this organism was activation to 3-hydroxy-benzoyl-CoA in an ATP-consuming reaction. Cell extracts of 3-hydroxybenzoate-grown cells exhibited 3-hydroxybenzoyl-CoA synthetase activity of 190 nmol min-1 mg protein-1 as well as benzoyl-CoA synthetase activity of 86 nmol min-1 mg protein-1. A reductive dehydroxylation of 3-hydroxybenzoyl-CoA could not be demonstrated due to rapid hydrolysis of chemically synthesized 3-hydroxybenzoyl-CoA by cell extracts.