Coupling factor 6-induced activation of ecto-F1F(o) complex induces insulin resistance, mild glucose intolerance and elevated blood pressure in mice

Identification of a gene network driving the attenuated response to lipopolysaccharide of monocytes from hypertensive coronary artery disease patients

Introduction

The impact of cardiovascular disease (CVD) risk factors, encompassing various biological determinants and unhealthy lifestyles, on the functional dynamics of circulating monocytes-a pivotal cell type in CVD pathophysiology remains elusive. In this study, we aimed to elucidate the influence of CVD risk factors on monocyte transcriptional responses to an infectious stimulus.

Methods

We conducted a comparative analysis of monocyte gene expression profiles from the CTMM - CIRCULATING CELLS Cohort of coronary artery disease (CAD) patients, at baseline and after lipopolysaccharide (LPS) stimulation. Gene co-expression analysis was used to identify gene modules and their correlations with CVD risk factors, while pivotal transcription factors controlling the hub genes in these modules were identified by regulatory network analyses. The identified gene module was subjected to a drug repurposing screen, utilizing the LINCS L1000 database.

Results

Monocyte responsiveness to LPS showed a highly significant, negative correlation with blood pressure levels (ρ< -0.4; P<10-80). We identified a ZNF12/ZBTB43-driven gene module closely linked to diastolic blood pressure, suggesting that monocyte responses to infectious stimuli, such as LPS, are attenuated in CAD patients with elevated diastolic blood pressure. This attenuation appears associated with a dampening of the LPS-induced suppression of oxidative phosphorylation. Finally, we identified the serine-threonine inhibitor MW-STK33-97 as a drug candidate capable of reversing this aberrant LPS response.

Conclusions

Monocyte responses to infectious stimuli may be hampered in CAD patients with high diastolic blood pressure and this attenuated inflammatory response may be reversed by the serine-threonine inhibitor MW-STK33-97. Whether the identified gene module is a mere indicator of, or causal factor in diastolic blood pressure and the associated dampened LPS responses remains to be determined.

Intracellular protons accelerate aging and switch on aging hallmarks in mice

Diet-induced metabolic acidosis is associated with the impairment of bone metabolism and an increased risk of a number of chronic noncommunicable diseases, such as type 2 diabetes mellitus and hypertension. The serum bicarbonate level is an independent predictor of chronic kidney disease progression. We investigated whether proton accelerates aging by analyzing both coupling factor 6-overexpressing transgenic (TG) and high salt-fed mice which display sustained intracellular acidosis, due to enhanced proton import through ecto-F₁ F_o complex and/or reduced proton export through Na⁺ -K⁺ ATPase inhibition. Both types of mice displayed shortened lifespan and early senescence-associated phenotypes such as signs of hair greying and alopecia, weight loss, and/or reduced organ mass. In chronic intracellular acidosis mice, autophagy was impaired by regression of Atg7, an increase in nuclear acetylated LC3 II, and acetylation of Atg7. The increase in histone 3 trimethylation at lysine 4 (H3K4me3) and H4K20me3 and the decrease in H3K9me3 and H3K27me3 were observed in the heart and kidney obtained from both TG and high salt-fed mice. The decrease in lamin A/C, emerin, and heterochromatin protein 1α without changes in barrier-to-autointegration factor and high-mobility group box 1 was confirmed in TG and high salt-fed mice. Suppression of nuclear histone deacetylase 3-emerin system is attributable to epigenetic regression of Atg7 and H4K5 acetylation. These findings will shed light on novel aging and impaired autophagy mechanism, and provide implications in a target for antiaging therapy.

Mitochondrial inhibitory factor protein 1 attenuates coupling factor 6-induced aging signal

Coupling factor 6 (CF6) forces a counter-clockwise rotation of plasma membrane F1 Fo complex, resulting in proton import and accelerated aging. Inhibitory factor peptide 1 (IF1) suppresses a unidirectional counter-clockwise rotation of F1 Fo complex without affecting ATP synthesis. We tested the hypothesis that IF1 may attenuate CF6-induced aging signaling in CF6-overexpressing transgenic (TG) cells. In IF1-GFP overexpressing wild type (WT) cells, the diffuse peripheral staining of tubular mitochondria was observed with a dense widely distributed network around the nucleus. In TG cells, however, the only peri-nuclear network of fragmented mitochondria was observed at 24 h, but it was developed to a widely distributed mitochondrial network of tubular mitochondria at 72 h. TG cells displayed aging hallmarks of telomere attrition, epigenetic alterations, defective proteostasis, and genomic instability with a decrease in emerin and lamin and loss of heterochromatin. IF1 induction rescued TG cells from telomere attrition, expression of genomic instability with the increase in emerin and lamin, and that of epigenetic alterations with recovery of heterochromatin. In defective proteostasis, IF1 induction restored a potent peri-nuclear staining of autolysosomes compared with the baseline weak staining. The decrease in Atg7 was restored, whereas the increase in P62 was abolished. We conclude that genetic disruption of proton signals by IF1 induction suppressed CF6-induced expression of aging hallmarks such as telomere attrition, epigenetic alterations, defective proteostasis, and genomic instability. Given the widespread biological actions of CF6, the physiological and pathological actions of IF1 may be complex.

Marine collagen peptides reduce endothelial cell injury in diabetic rats by inhibiting apoptosis and the expression of coupling factor 6 and microparticles

The present study aimed to elucidate the role of marine collagen peptides (MCPs) in protection of carotid artery vascular endothelial cells (CAVECs) in type 2 diabetes mellitus (T2DM), and the mechanism underlying this process. In an in vivo experiment, diabetic Wistar rats were divided randomly into four groups (n=10/group): Diabetes control, and three diabetes groups administered low, medium and high doses of MCPs (2.25, 4.5 and 9.0 g/kg body weight/day, respectively). Another 10 healthy rats served as the control. In an in vitro experiment, human umbilical‑vein endothelial cells (HUVECs) were incubated in normal and high concentrations of glucose with or without MCPs (3.0, 15.0 and 30.0 mg/ml, respectively) for 24, 48 or 72 h. Blood vessel/endothelial construction, inflammatory exudation and associated molecular biomarkers in CAVECs were detected and analyzed. The results of the present study demonstrated that in rats, MCP treatment for 4 weeks significantly lowered blood glucose and attenuated endothelial thinning and inflammatory exudation in carotid‑artery vascular endothelial cells. In vitro, the high‑glucose intervention significantly increased cell apoptosis in HUVECs, and medium and high doses of MCPs (4.5 and 9.0 g/kg body weight/day, respectively) partially ameliorated this high glucose‑mediated apoptosis and decreased levels of apoptosis biomarkers. In conclusion, a moderate oral MCP dose (≥4.5 g/kg body weight/day) may be a novel therapeutic tool to protect against early cardiovascular complications associated with T2DM by inhibiting apoptosis and reducing the expression of coupling factor 6 and microparticles.

Nutritional regulation of coupling factor 6, a novel vasoactive and proatherogenic peptide

High sodium, high glucose, and obesity are important risk factors for age-related diseases such as cardiovascular disease (CVDs), stroke, and cancer. Coupling factor 6 (CF6) is released from vascular endothelial cells and functions as a circulating peptide that inhibits prostacyclin and nitric oxide generation by intracellular acidosis. High glucose elevates CF6 by activation of protein kinase C and p38 mitogen-activated protein kinase, whereas CF6 causes type 2 diabetes mellitus, resulting in a high glucose vicious cycle. Low glucose increases inhibitory factor peptide 1, an endogenous inhibitor of CF6. High salt intake increases CF6 through nuclear factor κB signaling, whereas CF6 induces salt-sensitive hypertension and salt-induced congestive heart failure. Oral administration of vitamin C cancels salt-induced increase in CF6, and estrogen replacement leads to the delayed onset of CF6-induced salt-sensitive hypertension and the rescue from cardiac systolic dysfunction. Because CF6 contributes to the onset of CVDs, nutritional regulation of CF6 will shed light on the understanding of preventive strategy and mechanisms for CVDs and a target for therapy.

Lung-specific RNA interference of coupling factor 6, a novel peptide, attenuates pulmonary arterial hypertension in rats

Background

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease associated with high morbidity and mortality rates. However, the exact regulatory mechanism of PAH is unknown. Although coupling factor 6 (CF6) is known to function as a repressor, its role in PAH has not been explored. Here, we investigated the involvement of endogenous CF6 in the development of PAH.

Methods

PAH was induced with monocrotaline (MCT), as demonstrated by significant increases in pulmonary artery pressure and vessel wall thickness. The adeno-associated virus (AAV) carrying CF6 short hairpin RNA (shRNA) or control vector (2×10¹⁰ gp) was intratracheally transfected into the lungs of rats 2 weeks before or after MCT injection.

Results

A 2-6-fold increase in CF6 was observed in the lungs and circulation of the MCT-injected rats as confirmed by qRT-PCR and ELISA. Immunohistochemistry analysis revealed a small quantity of CF6 localized to endothelial cells (ECs) under physiological conditions spread to surrounding tissues in a paracrine manner in PAH lungs. Notably, CF6 shRNA effectively inhibited CF6 expression, abolished lung macrophage infiltration, reversed endothelial dysfunction and vascular remodeling, and ameliorated the severity of pulmonary hypertension and right ventricular dysfunction at 4 weeks both as a pretreatment and rescue intervention. In addition, the circulating and lung levels of 6-keto-PGF1a, a stable metabolite of prostacyclin, were reversed by CF6 inhibition, suggesting that the effect of CF6 inhibition may partly be mediated through prostacyclin.

Conclusions

CF6 contributes to the pathogenesis of PAH, probably in association with downregulation of prostacyclin. The blockage of CF6 might be applied as a novel therapeutic approach for PAH and PA remodeling.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0409-5) contains supplementary material, which is available to authorized users.

Mitochondrial Inhibitory Factor Protein 1 Functions as an Endogenous Inhibitor for Coupling Factor 6

Coupling factor 6 (CF6) forces a counter-clockwise rotation of plasma membrane F1 Fo complex unlike a proton-mediated clockwise rotation in the mitochondria, resulting in ATP hydrolysis, proton import, and apoptosis. Inhibitory peptide 1 (IF1) inhibits a unidirectional counter-clockwise rotation of F1 Fo complex without affecting ATP synthesis by a clockwise rotation. We tested the hypothesis that IF1 may antagonize the biological action of CF6 in human embryonic kidney 293 cells. We generated mature and immature IF1 expression vectors and those labeled with GFP at the C-terminus. In the immature IF1-GFP overexpressing cells, the mitochondrial network of IF1-GFP was newly found at the plasma membrane after peripheral translocation, whereas in mature IF1-GFP transfected cells, a less punctuate rather homogenous pattern was found in the cytoplasm. IF1 protein was detected in the exosome fraction of culture media, and it was enhanced by mature or immature IF1 transfection. Extracellular ATP hydrolysis was enhanced by CF6, whereas immature or mature IF1 transfection suppressed ATP hydrolysis in response to CF6. Intracellular pH was decreased by CF6 but was unchanged after immature IF1 transfection. CF6-induced increase in apoptotic cells was blocked by immature or mature IF1, being accompanied by protein kinase B (PKB) phosphorylation. IF1 antagonizes the pro-apoptotic action of CF6 by relief of intracellular acidification and resultant phosphorylation of PKB. Given the widespread biological actions of CF6, the physiological and pathological functions of IF1 may be expected to be complex. J. Cell. Biochem. 117: 1680-1687, 2016. © 2015 Wiley Periodicals, Inc.

F1FO ATP Synthase Is Expressed at the Surface of Embryonic Rat Heart-Derived H9c2 Cells and Is Affected by Cardiac-Like Differentiation

Taking advantage from the peculiar features of the embryonic rat heart-derived myoblast cell line H9c2, the present study is the first to provide evidence for the expression of F1FO ATP synthase and of ATPase Inhibitory Factor 1 (IF1) on the surface of cells of cardiac origin, together documenting that they were affected through cardiac-like differentiation. Subunits of both the catalytic F1 sector of the complex (ATP synthase-β) and of the peripheral stalk, responsible for the correct F1-FO assembly/coupling, (OSCP, b, F6) were detected by immunofluorescence, together with IF1. The expression of ATP synthase-β, ATP synthase-b and F6 were similar for parental and differentiated H9c2, while the levels of OSCP increased noticeably in differentiated cells, where the results of in situ Proximity Ligation Assay were consistent with OSCP interaction within ecto-F1FO complexes. An opposite trend was shown by IF1 whose ectopic expression appeared greater in the parental H9c2. Here, evidence for the IF1 interaction with ecto-F1FO complexes was provided. Functional analyses corroborate both sets of data. i) An F1FO ATP synthase contribution to the exATP production by differentiated cells suggests an augmented expression of holo-F1FO ATP synthase on plasma membrane, in line with the increase of OSCP expression and interaction considered as a requirement for favoring the F1-FO coupling. ii) The absence of exATP generation by the enzyme, and the finding that exATP hydrolysis was largely oligomycin-insensitive, are in line in parental cells with the deficit of OSCP and suggest the occurrence of sub-assemblies together evoking more regulation by IF1.

Opposite phenotypes of muscle strength and locomotor function in mouse models of partial trisomy and monosomy 21 for the proximal Hspa13-App region

The trisomy of human chromosome 21 (Hsa21), which causes Down syndrome (DS), is the most common viable human aneuploidy. In contrast to trisomy, the complete monosomy (M21) of Hsa21 is lethal, and only partial monosomy or mosaic monosomy of Hsa21 is seen. Both conditions lead to variable physiological abnormalities with constant intellectual disability, locomotor deficits, and altered muscle tone. To search for dosage-sensitive genes involved in DS and M21 phenotypes, we created two new mouse models: the Ts3Yah carrying a tandem duplication and the Ms3Yah carrying a deletion of the Hspa13-App interval syntenic with 21q11.2-q21.3. Here we report that the trisomy and the monosomy of this region alter locomotion, muscle strength, mass, and energetic balance. The expression profiling of skeletal muscles revealed global changes in the regulation of genes implicated in energetic metabolism, mitochondrial activity, and biogenesis. These genes are downregulated in Ts3Yah mice and upregulated in Ms3Yah mice. The shift in skeletal muscle metabolism correlates with a change in mitochondrial proliferation without an alteration in the respiratory function. However, the reactive oxygen species (ROS) production from mitochondrial complex I decreased in Ms3Yah mice, while the membrane permeability of Ts3Yah mitochondria slightly increased. Thus, we demonstrated how the Hspa13-App interval controls metabolic and mitochondrial phenotypes in muscles certainly as a consequence of change in dose of Gabpa, Nrip1, and Atp5j. Our results indicate that the copy number variation in the Hspa13-App region has a peripheral impact on locomotor activity by altering muscle function.

Coupling factor 6 enhances the spontaneous microaggregation of platelets by decreasing cytosolic cAMP irrespective of antiplatelet therapy

The spontaneous microaggregation of platelets (SMAPs) is a marker for the prognosis of patients with cardiovascular diseases. Coupling factor 6 (CF6) binds to the plasma membrane ATP synthase and functions as a pro-atherogenic molecule in the cardiovascular system. However, the role of CF6 in SMAPs and stroke remains unknown. In 650 consecutive patients, including those with acute-onset stroke, and 20 control subjects, platelet-rich plasma (PRP) was obtained, and SMAP was measured using a laser light-scattering aggregometer. The cytosolic cyclic adenosine monophosphate (cAMP) concentration in platelets was measured using an enzyme-linked immunosorbent assay. CF6 increased SMAPs in patients and control subjects to a similar degree by binding to the α- and β-subunits of ATP synthase and inducing intracellular acidosis. It was abolished by PRP pretreatment with antibodies against CF6, and the α- or β-subunit of the plasma membrane ATP synthase, and the ATP synthase inhibitor efrapeptin. CF6 increased SMAPs in patient groups with and without antiplatelet therapy to a similar degree, and no difference was found among the subgroups taking aspirin, thienopyridine or cilostazol. The cytosolic cAMP concentration in platelets was decreased by CF6 in the presence of the direct adenylate cyclase activator forskolin. Pretreatment of PRP with the Gs activator cholera toxin blocked the decrease, whereas the Gi inactivator pertussis toxin and cilostazol had no influence. The CF6-induced acceleration of SMAPs was suppressed by cholera toxin but not by cilostazol or pertussis toxin. CF6 enhanced SMAPs by decreasing cytosolic cAMP. Because it was observed irrespective of antiplatelet agents, CF6 appears to be a novel target for antiplatelet therapy.

Role of mineralocorticoid receptor in insulin resistance

PURPOSE OF REVIEW

Recent data suggest that mineralocorticoid receptor activation can affect insulin resistance independent of its effects on blood pressure. This review discusses new evidence linking mineralocorticoid receptor to insulin resistance and the underlying mechanisms of these effects.

RECENT FINDINGS

Observational studies have shown mineralocorticoid activity to be associated with insulin resistance irrespective of race, blood pressure or body weight. Increased mineralocorticoid activity may be the common link between obesity, hypertension, dyslipidemia and insulin resistance, features that make up the metabolic syndrome. Treatment of primary aldosteronism is associated with a decrease in insulin resistance and provides one of the most convincing evidences in favor of the contribution of mineralocorticoid receptor to insulin resistance. Dietary salt restriction, which increases aldosterone levels, is also associated with an increase in insulin resistance. Potential mechanisms by which mineralocorticoid receptor may contribute to insulin resistance include a decreased transcription of the insulin receptor gene, increased degradation of insulin receptor substrates, interference with insulin signaling mechanisms, decreased adiponectin production and increased oxidative stress and inflammation. Advantages of mineralocorticoid receptor antagonists on insulin resistance have been demonstrated in animal models.

SUMMARY

There may be a benefit of mineralocorticoid receptor antagonists in human insulin resistance states, but more clinical research is needed to explore these possibilities.

Estrogen attenuates coupling factor 6-induced salt-sensitive hypertension and cardiac systolic dysfunction in mice

In male coupling factor 6 (CF6)-overexpressing transgenic (TG) mice, a high-salt diet induces hypertension and cardiac systolic dysfunction with excessive reactive oxygen species generation. However, the role of gender in CF6-mediated pathophysiology is unknown. We investigated the effects of ovariectomy and estrogen replacement on hypertension, cardiac dysfunction and Rac1 activity, which activates radical generation and the mineralocorticoid receptor, in female TG mice. Fifteen-week-old male and female TG and wild-type (WT) mice were fed a normal- or high-salt diet for 60 weeks. Systolic and diastolic blood pressures were higher in the TG mice fed a high-salt diet than in those fed a normal-salt diet at 20-60 weeks in males but only at 60 weeks in females. The blood pressure elevation under high-salt diet conditions was concomitant with a decrease in left ventricular fractional shortening. In the WT mice, neither blood pressure nor cardiac systolic function was influenced by a high-salt diet. In the female TG mice, bilateral ovariectomy induced hypertension with cardiac systolic dysfunction 8 weeks after the initiation of a high-salt diet. The ratios of Rac1 bound to guanosine triphosphate (Rac1-GTP) to total Rac1 in the heart and kidneys were increased in the ovariectomized TG mice, and estrogen replacement abolished the CF6-mediated pathophysiology induced under the high-salt diet conditions. The overexpression of CF6 induced salt-sensitive hypertension, complicated by systolic cardiac dysfunction, but its onset was delayed in females. Estrogen has an important role in the regulation of CF6-mediated pathophysiology, presumably via the downregulation of Rac1.

Identification and characterization of a highly thermostable bacteriophage lysozyme

Pseudomonas aeruginosa bacteriophage phiKMV is a T7-like lytic phage. Liquid chromatography-mass spectrometry of the structural proteins revealed gene product 36 (gp36) as part of the phiKMV phage particle. The presence of a lysozyme domain in the C terminal of this protein (gp36C) was verified by turbidimetric assays on chloroform-treated P. aeruginosa PAO1 and Escherichia coli WK6 cells. The molecular mass (20,884 Da) and pI (6.4) of recombinant gp36C were determined, as were the optimal enzymatic conditions (pH 6.0 in 16.7 mM phosphate buffer) and activity (4800 U/mg). Recombinant gp36C is a highly thermostable lysozyme, retaining 26% of its activity after 2 h at 100 degrees C and 21% after autoclaving. This thermostability could prove an interesting characteristic for food conservation technology.