Environmental Stressors and the PINE Network: Can Physical Environmental Stressors Drive Long-Term Physical and Mental Health Risks?

Both psychosocial and physical environmental stressors have been linked to chronic mental health and chronic medical conditions. The psycho-immune-neuroendocrine (PINE) network details metabolomic pathways which are responsive to varied stressors and link chronic medical conditions with mental disorders, such as major depressive disorder via a network of pathophysiological pathways. The primary objective of this review is to explore evidence of relationships between airborne particulate matter (PM, as a concrete example of a physical environmental stressor), the PINE network and chronic non-communicable diseases (NCDs), including mental health sequelae, with a view to supporting the assertion that physical environmental stressors (not only psychosocial stressors) disrupt the PINE network, leading to NCDs. Biological links have been established between PM exposure, key sub-networks of the PINE model and mental health sequelae, suggesting that in theory, long-term mental health impacts of PM exposure may exist, driven by the disruption of these biological networks. This disruption could trans-generationally influence health; however, long-term studies and information on chronic outcomes following acute exposure event are still lacking, limiting what is currently known beyond the acute exposure and all-cause mortality. More empirical evidence is needed, especially to link long-term mental health sequelae to PM exposure, arising from PINE pathophysiology. Relationships between physical and psychosocial stressors, and especially the concept of such stressors acting together to impact on PINE network function, leading to linked NCDs, evokes the concept of syndemics, and these are discussed in the context of the PINE network.

A novel radiographic method to facilitate measurement of the tibial plateau angle in dogs

The tibial plateau levelling osteotomy (TPLO) is commonly performed for treatment of cranial cruciate ligament deficiency in dogs. In order to be performed as described, this procedure relies on consistent measurement of the tibial plateau angle (TPA) on radiographs. This prospective study compared two radiographic methods for subsequent TPA measurement with respect to measured angle and ease of determining landmarks for measurement as determined by four observers. One method was the accepted standard radiographic protocol outlined in the TPLO training seminars. The other method involved a novel split image radiographic protocol not yet described in the literature. Participants' subjective scores as to ease of identifying landmarks and determining TPA on radiographs for each method were evaluated. Inter-observer TPA measurement variability was also assessed for each method. The novel radiographic method was judged to be significantly better in terms of ease of measuring TPA. Inter-observer measurement variability was considered appropriate for recommending use of this novel method for radiographing patients for TPA measurements.

Abstract 220: Transcriptional Analysis Of Caveolin And Cavin In The Male And Female Ageing Mouse Heart Following Ischemic Stress

Cardioprotection against infarction and dysfunction in the myocardium involves G-protein-coupled receptor signalling orchestrated by specialised membrane microdomains termed caveolae. The caveolin protein family consist of three subtypes: caveolin-1, −2 and −3 (Cav1-3) and are responsible for the formation of caveolae and hypothesized to orchestrate cardioprotective signalling. Caveolin-3 deficiency and overexpression has been shown to attenuate and restore cardioprotection, respectively. Recently, a family of four related proteins known as cavins (Cavin1-4) have been implicated as regulators of caveolae formation and function. The roles and expression distribution of the cavin family is currently unknown in cardiac tissue. In this study hearts were isolated from 8, 16, 32 and 48 week male and female mice and subjected to normoxic perfusion (80 min) or ischemic stress (20 min global ischemia, 60 min reperfusion). RT-qPCR was used to assess differential gene expression of caveolin and cavin subtypes across these ages in both sexes.

Decreased post-ischemic pressure development and increased LDH release were observed in 32 and 48 week old relative to 8 week old male hearts hearts, indicative of age-related loss of ischemic tolerance. Females showed greater tolerance to ischemia at 32 and 48 week old hearts when compared to male counterparts. In normoxic male 48 week old hearts, Cav1,-2,-3 and Cavin1 were significantly repressed, whilst post-ischemic male 48 week old hearts demonstrated significant repression of Cav3 and Cavin1 only. Normoxic female hearts showed no significant changes in caveolin and cavin transcript expression over the aging time course. However, post-ischemic female 48 week old hearts showing significant down-regulation of Cav3 only. Taken together, alterations in caveolin and cavin expression may contribute to the age-related loss of ischemic tolerance and G-protein-coupled receptor-mediated protection in aging male and female mice hearts.

Loss of caveolin-1 accelerates neurodegeneration and aging

BACKGROUND

The aged brain exhibits a loss in gray matter and a decrease in spines and synaptic densities that may represent a sequela for neurodegenerative diseases such as Alzheimer's. Membrane/lipid rafts (MLR), discrete regions of the plasmalemma enriched in cholesterol, glycosphingolipids, and sphingomyelin, are essential for the development and stabilization of synapses. Caveolin-1 (Cav-1), a cholesterol binding protein organizes synaptic signaling components within MLR. It is unknown whether loss of synapses is dependent on an age-related loss of Cav-1 expression and whether this has implications for neurodegenerative diseases such as Alzheimer's disease.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed brains from young (Yg, 3-6 months), middle age (Md, 12 months), aged (Ag, >18 months), and young Cav-1 KO mice and show that localization of PSD-95, NR2A, NR2B, TrkBR, AMPAR, and Cav-1 to MLR is decreased in aged hippocampi. Young Cav-1 KO mice showed signs of premature neuronal aging and degeneration. Hippocampi synaptosomes from Cav-1 KO mice showed reduced PSD-95, NR2A, NR2B, and Cav-1, an inability to be protected against cerebral ischemia-reperfusion injury compared to young WT mice, increased Aβ, P-Tau, and astrogliosis, decreased cerebrovascular volume compared to young WT mice. As with aged hippocampi, Cav-1 KO brains showed significantly reduced synapses. Neuron-targeted re-expression of Cav-1 in Cav-1 KO neurons in vitro decreased Aβ expression.

CONCLUSIONS

Therefore, Cav-1 represents a novel control point for healthy neuronal aging and loss of Cav-1 represents a non-mutational model for Alzheimer's disease.

Myocardial Ischemia-Reperfusion Injury, Antioxidant Enzyme Systems, and Selenium: A Review

Coronary heart disease (CHD) remains the greatest killer in the Western world, and although the death rate from CHD has been falling, the current increased prevalence of major risk factors including obesity and diabetes, suggests it is likely that CHD incidence will increase over the next 20 years. In conjunction with preventive strategies, major advances in the treatment of acute coronary syndromes and myocardial infarction have occurred over the past 20 years. In particular the ability to rapidly restore blood flow to the myocardium during heart attack, using interventional cardiologic or thrombolytic approaches has been a major step forward. Nevertheless, while 'reperfusion' is a major therapeutic aim, the process of ischemia followed by reperfusion is often followed by the activation of an injurious cascade. While the pathogenesis of ischemia-reperfusion is not completely understood, there is considerable evidence implicating reactive oxygen species (ROS) as an initial cause of the injury. ROS formed during oxidative stress can initiate lipid peroxidation, oxidize proteins to inactive states and cause DNA strand breaks, all potentially damaging to normal cellular function. ROS have been shown to be generated following routine clinical procedures such as coronary bypass surgery and thrombolysis, due to the unavoidable episode of ischemia-reperfusion. Furthermore, they have been associated with poor cardiac recovery post-ischemia, with recent studies supporting a role for them in infarction, necrosis, apoptosis, arrhythmogenesis and endothelial dysfunction following ischemia-reperfusion. In normal physiological condition, ROS production is usually homeostatically controlled by endogenous free radical scavengers such as superoxide dismutase, catalase, and the glutathione peroxidase and thioredoxin reductase systems. Accordingly, targeting the generation of ROS with various antioxidants has been shown to reduce injury following oxidative stress, and improve recovery from ischemia-reperfusion injury. This review summarises the role of myocardial antioxidant enzymes in ischemia-reperfusion injury, particularly the glutathione peroxidase (GPX) and the thioredoxin reductase (TxnRed) systems. GPX and TxnRed are selenocysteine dependent enzymes, and their activity is known to be dependent upon an adequate supply of dietary selenium. Moreover, various studies suggest that the supply of selenium as a cofactor also regulates gene expression of these selenoproteins. As such, dietary selenium supplementation may provide a safe and convenient method for increasing antioxidant protection in aged individuals, particularly those at risk of ischemic heart disease, or in those undergoing clinical procedures involving transient periods of myocardial hypoxia.

A novel radiographic method to facilitate measurement of the tibial plateau angle in dogs. A prospective clinical study

The tibial plateau levelling osteotomy (TPLO) is commonly performed for treatment of cranial cruciate ligament deficiency in dogs. In order to be performed as described, this procedure relies on consistent measurement of the tibial plateau angle (TPA) on radiographs. This prospective study compared two radiographic methods for subsequent TPA measurement with respect to measured angle and ease of determining landmarks for measurement as determined by four observers. One method was the accepted standard radiographic protocol outlined in the TPLO training seminars. The other method involved a novel split image radiographic protocol not yet described in the literature. Participants' subjective scores as to ease of identifying landmarks and determining TPA on radiographs for each method were evaluated. Inter-observer TPA measurement variability was also assessed for each method. The novel radiographic method was judged to be significantly better in terms of ease of measuring TPA. Inter-observer measurement variability was considered appropriate for recommending use of this novel method for radiographing patients for TPA measurements.

Selenium supplementation and ischemia-reperfusion injury in rats

Cardiac ischemia--reperfusion injury results in oxidative stress and poor physiological recovery. This study examined the amount of lipid and protein oxidation during ischemia-reperfusion to assess the degree of oxidative stress. Selenium supplementation was used to alter the antioxidant status of rats and the recovery of myocardial function post ischemia-reperfusion was investigated. Male Wistar rats were fed diets containing 0, 50, and 1000 microg/kg sodium selenite for 5 weeks, whilst controls received normal rat food containing 240 microg/kg selenium. Langendorff-perfused hearts were subjected to 22.5 min global ischemia and 45 min reperfusion, with functional recovery assessed. Heart tissues were assayed for the presence of lipid peroxides and protein carbonyls and correlated to cardiac recovery. Following ischemia and reperfusion there was a significant increase in both protein oxidation and lipid peroxidation. Hearts from selenium-deficient animals demonstrated higher levels of both protein carbonyls and lipid peroxides and were more susceptible to ischemia-reperfusion injury when compared to controls (38% versus 47% recovery of rate pressure product (RPP)). Selenium supplementation lowered the levels of protein carbonyls and lipid peroxides and resulted in improved recovery of cardiac function post ischemia-reperfusion (57% recovery of RPP). These data suggest that selenium supplementation may provide an effective method for reducing oxidative damage post cardiac ischemia-reperfusion.

Effects of dietary selenium on post-ischemic expression of antioxidant mRNA

Cardiac ischemia reperfusion leads to oxidative stress and poor physiological recovery. Selenium deficiency down-regulates thioredoxin reductase (Txnrd) and glutathione peroxidase (Gpx) activity, impairing recovery from ischemia-reperfusion. Furthermore, selenium supplementation has been shown to be cardioprotective and lessens oxidative stress in reperfused rat hearts. In this study we have investigated the role of selenium in the mRNA expression of these, and related antioxidant proteins, post ischemia-reperfusion. Male rats were fed varying doses of selenium for five weeks. Hearts were isolated and perfused using the Langendorff method with 22.5 min of global ischemia and 45 min reperfusion. RNA was extracted for quantitative real-time PCR analysis of glutathione peroxidase (Gpx)-1 and 4, glutathione reductase (Gsr), thioredoxin peroxidase-2 (Prdx2), thioredoxin (Txn) and thioredoxin reductase (Txnrd)-1 and 2 gene expression. Selenium deficiency produced significant reductions in Gpx-1, Gpx-4, Prdx2, Txnrd-1 and Txnrd-2 expression. Conversely, selenium supplementation of 1000 microg/kg significantly up-regulated Gpx-1, Gpx-4, Txn, Txnrd-1 and Txnrd-2 transcription. Our results show selenium modulates the cardiac mRNA expression of thioredoxin and glutathione related enzymes post ischemia-reperfusion, and impacts on tolerance to ischemia-reperfusion.

AURANOFIN INCREASES APOPTOSIS AND ISCHAEMIA-REPERFUSION INJURY IN THE RAT ISOLATED HEART

Auranofin, an antirheumatic gold compound, is an inhibitor of selenocysteine enzymes, such as thioredoxin reductase and glutathione peroxidase. These enzymes play an important role in protecting cardiac tissue from oxidative stress generated during ischaemia-reperfusion. Auranofin (100 mg/kg) was administered to rats and their hearts were subjected to an in vitro model of ischaemia-reperfusion. The activity of thioredoxin reductase and glutathione peroxidase was determined in liver and heart tissues in an attempt to correlate enzymatic activity with heart recovery after ischaemia-reperfusion. There was significantly less thioredoxin reductase activity in rat liver extracts, whereas the level of glutathione activity remained unchanged, demonstrating that the dose of auranofin used was able to selectively inhibit one of these enzyme systems. Rats administered auranofin displayed significantly impaired recovery from ischaemic insult. The end diastolic pressure was increased, whereas the rate pressure product was significantly decreased. The level of postischaemic apoptosis was also assessed by examining caspase-3 activity in tissue homogenates. Auranofin significantly increased the degree of postischaemic apoptosis, leading to poor postischaemic recovery.

Effects of dietary selenium on glutathione peroxidase and thioredoxin reductase activity and recovery from cardiac ischemia-reperfusion

Glutathione peroxidase and thioredoxin reductase are selenocysteine-dependent enzymes that protect against oxidative injury. This study examined the effects of dietary selenium on the activity of these two enzymes in rats, and investigated the ability of selenium to modulate myocardial function post ischemia-reperfusion. Male wistar rats were fed diets containing 0, 50, 240 and 1000 microg/kg sodium selenite for 5 weeks. Langendorff perfused hearts isolated from these rats were subjected to 22.5 min global ischemia and 45 min reperfusion, with functional recovery assessed. Liver samples were collected at the time of sacrifice, and heart and liver tissues assayed for thioredoxin reductase and glutathione peroxidase activity. Selenium deficiency reduced the activity of both glutathione peroxidase and thioredoxin reductase systemically. Hearts from selenium deficient animals were more susceptible to ischemia-reperfusion injury when compared to normal controls (38% recovery of rate pressure product (RPP) vs. 47% recovery of RPP). Selenium supplementation increased the endogenous activity of thioredoxin reductase and glutathione peroxidase and resulted in improved recovery of cardiac function post ischemia reperfusion (57% recovery of RPP). Endogenous activity of glutathione peroxidase and thioredoxin reductase is dependent on an adequate supply of the micronutrient selenium. Reduced activity of these antioxidant enzymes is associated with significant reductions in myocardial function post ischemia-reperfusion.

Characterization of a split respiratory pathway in the wheat "take-all" fungus, Gaeumannomyces graminis var. tritici

This article describes the first detailed analysis of mitochondrial electron transfer and oxidative phosphorylation in the pathogenic filamentous fungus, Gaeumannomyces graminis var. tritici. While oxygen consumption was cyanide insensitive, inhibition occurred following treatment with complex III inhibitors and the alternative oxidase inhibitor, salicylhydroxamic acid (SHAM). Similarly, maintenance of a Deltapsi across the mitochondrial inner membrane was unaffected by cyanide but sensitive to antimycin A and SHAM when succinate was added as the respiratory substrate. As a result, ATP synthesis through complex V was demonstrated to be sensitive to these two inhibitors but not to cyanide. Analysis of the cytochrome content of mitochondria indicated the presence of those cytochromes normally associated with electron transport in eukaryotic mitochondria together with a third, b-type heme, exhibiting a dithionite-reduced absorbance maxima at 560 nm and not associated with complex III. Antibodies raised to plant alternative oxidase detected the presence of both the monomeric and dimeric forms of this oxidase. Overall this study demonstrates that a novel respiratory chain utilizing the terminal oxidases, cytochrome c oxidase and alternative oxidase, are present and constitutively active in electron transfer in G. graminis tritici. These results are discussed in relation to current understanding of fungal electron transfer and to the possible contribution of alternative redox centers in ATP synthesis.

A biphasic response to adenosine in the coronary vasculature of the K(+)-arrested perfused rat heart

Biphasic vasodilatory responses to adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) were observed in the coronary vasculature of K(+)-arrested perfused rat hearts. Dose-response data for both agonists were best represented by two-site models. For adenosine, two sites with negative log ED50 (pED50) values of 8.1 +/- 0.1 (mean +/- S.E.M) and 5.2 +/- 0.1 were obtained, mediating 31 +/- 2% and 69 +/- 2% of the total response. In the presence of 8-phenyltheophylline, the vasodilatory response to adenosine remained best fitted to a two-site model with pED50 values of 7.0 +/- 0.2 and 5.4 +/- 0.2. The relative contribution of each site to the total response remained unchanged. For NECA, pED50 values of 9.6 +/- 0.1 and 6.8 +/- 0.2 were obtained, representing 48 +/- 3% and 52 +/- 3% of the sites, respectively. In contrast, ATP produced a monophasic response with a pED50 value of 8.8 +/- 0.1. These results provide evidence of adenosine receptor and response heterogeneity in the in situ coronary vasculature.

Adenosine production and energy metabolism in ischaemic and metabolically stimulated rat heart

Adenosine may modulate blood flow and electrical activity in heart in response to changes in myocardial energy metabolism. In the present study, 31P NMR spectroscopy was used to examine the relation between cytosolic phosphate metabolite levels and release of adenosine into the venous effluent of isovolumic heart during graded low-flow ischaemia or metabolic stimulation with isoproterenol. When coronary flow rate was varied in steps between 1.6 and 12 ml/min/g, cytosolic ATP levels did not change significantly but the phosphorylation potential exhibited a linear correlation with flow rate below approximately 7 ml/min/g. Purine release (adenosine and inosine) correlated linearly with the cytosolic phosphorylation potential and free AMP concentration. Metabolic stimulation of hearts with isoproterenol (0.4, 3.0, and 60 nM), produced a significant fall in cytosolic ATP levels and decreased the cytosolic phosphorylation potential. Purine release in these hearts increased exponentially as the cytosolic phosphorylation potential dropped, and as cytosolic free AMP increased. These results support a link between the phosphorylation potential and the mechanism of adenosine production during ischaemia and metabolic stimulation. Presumably, this link is the activity of the enzyme 5'-nucleotidase, which is responsible for converting AMP to adenosine, together with the concentration of its substrate, AMP. In low-flow ischaemia, cytosolic AMP may control adenosine formation. With isoproterenol stimulation, a more complex relationship exists, indicating possible allosteric regulation of the enzyme(s) responsible for adenosine formation, in addition to changes in AMP concentration.