Increased in vivo mitochondrial oxygenation with right ventricular failure induced by pulmonary arterial hypertension: mitochondrial inhibition as driver of cardiac failure?

Background

The leading cause of mortality due to pulmonary arterial hypertension (PAH) is failure of the cardiac right ventricle. It has long been hypothesized that during the development of chronic cardiac failure the heart becomes energy deprived, possibly due to shortage of oxygen at the level of cardiomyocyte mitochondria. However, direct evaluation of oxygen tension levels within the in vivo right ventricle during PAH is currently lacking. Here we directly evaluated this hypothesis by using a recently reported technique of oxygen-dependent quenching of delayed fluorescence of mitochondrial protoprophyrin IX, to determine the distribution of mitochondrial oxygen tension (mitoPO₂) within the right ventricle (RV) subjected to progressive PAH.

Methods

PAH was induced through a single injection of monocrotaline (MCT). Control (saline-injected), compensated RV hypertrophy (30 mg/kg MCT; MCT30), and RV failure (60 mg/kg MCT; MCT60) rats were compared 4 wk after treatment. The distribution of mitoPO₂ within the RV was determined in mechanically-ventilated, anaesthetized animals, applying different inspired oxygen (FiO₂) levels and two increment dosages of dobutamine.

Results

MCT60 resulted in RV failure (increased mortality, weight loss, increased lung weight), MCT30 resulted in compensated RV hypertrophy. At 30% or 40% FiO₂, necessary to obtain physiological arterial PO₂ in the diseased animals, RV failure rats had significantly less mitochondria (15% of total mitochondria) in the 0-20 mmHg mitoPO₂ range than hypertrophied RV rats (48%) or control rats (54%). Only when oxygen supply was reduced to 21% FiO_2, resulting in low arterial PO₂ for the MCT60 animals, or when oxygen demand increased with high dose dobutamine, the number of failing RV mitochondria with low oxygen became similar to control RV. In addition, metabolic enzyme analysis revealed similar mitochondrial mass, increased glycolytic hexokinase activity following MCT, with increased lactate dehydrogenase activity only in compensated hypertrophied RV.

Conclusions

Our novel observation of increased mitochondrial oxygenation suggests down-regulation of in vivo mitochondrial oxygen consumption, in the absence of hypoxia, with transition towards right ventricular failure induced by pulmonary arterial hypertension.     

Myocardial dysfunction in rheumatoid arthritis: epidemiology and pathogenesis

Data from population- and clinic-based epidemiologic studies of rheumatoid arthritis patients suggest that individuals with rheumatoid arthritis are at risk for developing clinically evident congestive heart failure. Many established risk factors for congestive heart failure are over-represented in rheumatoid arthritis and likely account for some of the increased risk observed. In particular, data from animal models of cytokine-induced congestive heart failure have implicated the same inflammatory cytokines produced in abundance by rheumatoid synovium as the driving force behind maladaptive processes in the myocardium leading to congestive heart failure. At present, however, the direct effects of inflammatory cytokines (and rheumatoid arthritis therapies) on the myocardia of rheumatoid arthritis patients are incompletely understood.     

Regulation of IFN response gene activity during infliximab treatment in rheumatoid arthritis is associated with clinical response to treatment

Introduction  

Cross-regulation between TNF and type I IFN has been postulated to play an important role in autoimmune diseases. Therefore, we determined the effect of TNF blockade in rheumatoid arthritis (RA) on the type I IFN response gene activity in relation to clinical response.     

Disease-modifying antirheumatic drugs are associated with a reduced risk for cardiovascular disease in patients with rheumatoid arthritis: a case control study

Rheumatoid arthritis (RA) is characterized by inflammation and an increased risk for cardiovascular disease (CVD). This study investigates possible associations between CVD and the use of conventional disease-modifying antirheumatic drugs (DMARDs) in RA. Using a case control design, 613 RA patients (5,649 patient-years) were studied, 72 with CVD and 541 without CVD. Data on RA, CVD and drug treatment were evaluated from time of RA diagnosis up to the first cardiovascular event or the end of the follow-up period. The dataset was categorized according to DMARD use: sulfasalazine (SSZ), hydroxychloroquine (HCQ) or methotrexate (MTX). Odds ratios (ORs) for CVD, corrected for age, gender, smoking and RA duration, were calculated per DMARD group. Patients who never used SSZ, HCQ or MTX were used as a reference group. MTX treatment was associated with a significant CVD risk reduction, with ORs (95% CI): 'MTX only', 0.16 (0.04 to 0.66); 'MTX and SSZ ever', 0.20 (0.08 to 0.51); and 'MTX, SSZ and HCQ ever', 0.20 (0.08 to 0.54). The risk reductions remained significant after additional correction for the presence of rheumatoid factor and erosions. After correction for hypertension, diabetes and hypercholesterolemia, 'MTX or SSZ ever' and 'MTX, SSZ and HCQ ever' showed significant CVD risk reduction. Rheumatoid factor positivity and erosions both increased CVD risk, with ORs of 2.04 (1.02 to 4.07) and 2.36 (0.92 to 6.08), respectively. MTX and, to a lesser extent, SSZ were associated with significantly lower CVD risk compared to RA patients who never used SSZ, HCQ or MTX. We hypothesize that DMARD use, in particular MTX use, results in powerful suppression of inflammation, thereby reducing the development of atherosclerosis and subsequently clinically overt CVD.     

Studies of the transmissibility of the agent of bovine spongiform encephalopathy to the domestic chicken

Background

Escherichia coli O157:H7 is the most common serovar of enterohemorrhagic E. coli associated with serious human disease outbreaks. Cattle are the main reservoir with E. coli O157:H7 inducing hemorrhagic enteritis in persistent shedding beef cattle, however little is known about how this pathogen affects cattle health. Jejunal Hemorrhage Syndrome (JHS) has unclear etiology but the pathology is similar to that described for E. coli O157:H7 challenged beef cattle suggestive that E. coli O157:H7 could be involved. There are no effective treatments for JHS however new approaches to managing pathogen issues in livestock using prebiotics and probiotics are gaining support. The first objective of the current study was to characterize pathogen colonization in hemorrhaged jejunum of dairy cattle during natural JHS outbreaks. The second objective was to confirm the association of mycotoxigenic fungi in feeds with the development of JHS and also to identify the presence of potential mycotoxins. The third objective was to determine the impact of a prebiotic, Celmanax?, or probiotic, Dairyman's Choice? paste, on the cytotoxicity associated with feed extracts in vitro. The fourth objective was to determine the impact of a prebiotic or a probiotic on E. coli O157:H7 colonization of mucosal explants and a bovine colonic cell line in vitro. The final objective was to determine if prebiotic and probiotic feed additives could modify the symptoms that preceded JHS losses and the development of new JHS cases.

Findings

Dairy cattle developed JHS after consuming feed containing several types of mycotoxigenic fungi including Fusarium culmorum, F. poae, F. verticillioides, F. sporotrichioides, Aspergillus flavus, Penicillium roqueforti, P. crustosum, P. paneum and P. citrinum. Mixtures of Shiga toxin - producing Escherichia coli (STEC) colonized the mucosa in the hemorrhaged tissues of the cattle and no other pathogen was identified. The STECs expressed Stx1 and Stx2, but more significantly, Stxs were also present in the blood clot blocking the jejunum. Mycotoxin analysis of the corn crop confirmed the presence of fumonisin, NIV, ZEAR, DON, 15-ADON, 3-ADON, NEO, DAS, HT-2 and T-2. Feed extracts were toxic to enterocytes and 0.1% Celmanax? removed the cytotoxicity in vitro. There was no effect of Dairyman's Choice? paste on feed-extract activity in vitro. Fumonisin, T-2, ZEAR and DON were toxic to bovine cells and 0.1% Celmanax? removed the cytotoxicity in vitro. Celmanax? also directly decreased E. coli O157:H7 colonization of mucosal explants and a colonic cell line in a dose-dependent manner. There was no effect of Dairyman's Choice? paste on E. coli O157:H7 colonization in vitro. The inclusion of the prebiotic and probiotic in the feed was associated with a decline in disease.

Conclusion

The current study confirmed an association between mycotoxigenic fungi in the feed and the development of JHS in cattle. This association was further expanded to include mycotoxins in the feed and mixtures of STECs colonizing the severely hemorrhaged tissues. Future studies should examine the extent of involvement of the different STEC in the infection process. The prebiotic, Celmanax?, acted as an anti-adhesive for STEC colonization and a mycotoxin binder in vitro. Future studies should determine the extent of involvement of the prebiotic in altering disease.     

CD14 C-159T and early infection with Pseudomonas aeruginosa in children with cystic fibrosis

Early acquisition of Pseudomonas aeruginosa is associated with a poorer prognosis in patients with cystic fibrosis. We investigated whether polymorphisms in CD14, the lipopolysaccharide receptor, increase the risk of early infection. Forty-five children with cystic fibrosis were investigated with annual bronchoalveolar lavage (BAL) and plasma sCD14 levels. Plasma sCD14 levels were significantly lower in children from whom P.aeruginosa was subsequently isolated (492.75 μg/ml vs. 1339.43 μg/ml, p = 0.018). Those with the CD14 -159CC genotype had a significantly increased risk of early infection with P.aeruginosa suggesting that CD14 C-159T plays a role in determining the risk of early infection with P.aeruginosa.     

Individual mRNA expression profiles reveal the effects of specific microRNAs

Background  

MicroRNAs (miRNAs) are oligoribonucleotides with an important role in regulation of gene expression at the level of translation. Despite imperfect target complementarity, they can also significantly reduce mRNA levels. The validity of miRNA target gene predictions is difficult to assess at the protein level. We sought, therefore, to determine whether a general lowering of predicted target gene mRNA expression by endogenous miRNAs was detectable within microarray gene expression profiles.     

Effects of age and leg length upon central loop of the Gastrocnemius-soleus H-reflex latency

Background  

central loop of the gastrocnemius-soleus H-reflex latency (T_c) that looks promising in the diagnosis of S1 radiculopathy; has been investigated in a few studies and only two of them have focused on the constitutional factors affecting it. Although leg length has been shown to contribute to the T_c, the role of age is controversial. More confusing, none of the previously performed studies have used strict criteria to rule out subclinical neuropathy, so the results could be misleading. This study has been performed to determine the influence of leg length and age on T_c among a carefully selected group of healthy volunteers.     

The time course of inflammatory cytokine secretion in a rat model of postoperative pain does not coincide with the onset of mechanical hyperalgesia

We characterized the time course of inflammatory cytokine release at the site of injury and in plasma after surgery on the rat tail. Anesthetized Sprague-Dawley rats had a 20 mm long incision made through the skin and fascia of their tails. Control rats were anesthetized, but no incision was made. Blood and tissue samples were taken 2 h and 1, 2, 4, and 8 days after surgery and analysed by ELISA for interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and cytokine-induced neutrophil chemoattractant-1 (CINC-1). In another group of rats, daily behavioral measurements were made of the rats' responses to a blunt noxious mechanical stimulus (4 Newtons) applied to their tails. Primary hyperalgesia developed within 2 h of surgery and lasted for 6 days. The tissue concentrations of IL-1beta, IL-6, and CINC-1 increased within 24 h of surgery, and TNF-alpha concentration increased within 48 h of surgery. Thereafter, cytokine concentrations remained elevated for 4 (IL-1beta and IL-6) to 8 days (CINC-1, TNF-alpha) after surgery. Control animals did not develop hyperalgesia and no changes in cytokines concentrations were detected. Thus, in our model of postoperative pain, secretion of inflammatory cytokines IL-1beta, IL-6, TNF-alpha, and CINC-1 was not essential for the initiation of postoperative hyperalgesia.     

The effect of estrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women

This study assessed the influence of estrogen (E₂) on muscle damage biomarkers [skeletal muscle - creatine kinase (CK); cardiac muscle - CK-MB] responses to prolonged aerobic exercise. Eumenorrheic women (n=10) who were physically active completed two 60-minute treadmill running sessions at ∼60-65% maximal intensity during low E₂ (midfollicular menstrual phase) and high E₂ (midluteal menstrual phase) hormonal conditions. Blood samples were collected prior to exercise (following supine rest), immediately post-, 30 min post-, and 24 hours post-exercise to determine changes in muscle biomarkers. Resting blood samples confirmed appropriate E₂ hormonal levels Total CK concentrations increased following exercise and at 24 hours post-exercise were higher in the midfollicular low E₂ phase (p<0.001). However, CK-MB concentrations were unaffected by E₂ level or exercise (p=0.442) resulting in the ratio of CK-MB to total CK being consistently low in subject responses (i.e., indicative of skeletal muscle damage). Elevated E₂ levels reduce the CK responses of skeletal muscle, but had no effect on CK-MB responses following prolonged aerobic exercise. These findings support earlier work showing elevated E₂ is protective of skeletal muscle from exercise-induced damage associated with prolonged aerobic exercise.