Behavioural and electrophysiological characterisation of experimentally induced osteoarthritis and neuropathy in C57Bl/6 mice

Background: Osteoarthritis is a widespread condition affecting the elderly where similar to 70-90% of over 75 year olds are affected, representing one of the largest cost burdens to healthcare in the western world. The monosodium iodoacetate (MIA) osteoarthritis model has been well described in the rat especially in terms of the pathological progression of the disease and more recently pain behaviour. In this study, we characterise, for the first time, MIA induced osteoarthritis in mice and compare it with nerve-injured mice (partial sciatic nerve injury), using both behavioural and in vivo electrophysiological measurements. These approaches uniquely allow the threshold and suprathreshold measures to many modalities to be quantified and so form a basis for improving and expanding transgenic studies.Results: Significant mechanical hypersensitivity was observed in the ipsilateral hindpaw in MIA injected mice at all observed time points following infrapetellar MIA injection (p < 0.05). The mechanical hypersensitivity exhibited a partial biphasic temporal pattern, but thermal hypersensitivity was absent. Electrically-evoked dorsal horn neuronal responses in MIA injected mice were significantly elevated (p < 0.05) with respect to A- and C-fibre firing, input, pinch and noxious von Frey (26 and 60 g). No significant changes in A- or C-fibre thresholds were observed. Nerve-injured mice displayed significant behavioural thermal and mechanical hypersensitivity (p < 0.05) and evoked dorsal horn responses were significantly increased with respect to C-fibre firing, pinch and wind-up (p < 0.05).Conclusion: The MIA model of osteoarthritic pain in mice displays behavioural characteristics similar to those observed in rats. Changes in both behavioural measures and neuronal activity from the paw, suggest that central changes are involved in this pain state, although a role for peripheral drives is also likely. Moreover, the behavioural and neuronal measures in these two pain models showed overlapping alterations in terms of certain neuronal measures and mechanical sensitivity despite their very different pathologies and a loss of input in neuropathy, suggesting some commonalities in the central processing of different peripheral pain states. This murine model of osteoarthritis will allow the exploitation of knock out animals to better understand underlying mechanisms and identify novel molecular targets

A functional and transcriptomic analysis of NET1 bioactivity in gastric cancer

<p>Abstract</p> <p>Background</p> <p>NET1, a RhoA guanine exchange factor, is up-regulated in gastric cancer (GC) tissue and drives the invasive phenotype of this disease. In this study, we aimed to determine the role of NET1 in GC by monitoring the proliferation, motility and invasion of GC cells in which NET1 has been stably knocked down. Additionally, we aimed to determine NET1-dependent transcriptomic events that occur in GC.</p> <p>Methods</p> <p>An in vitro model of stable knockdown of NET1 was achieved in AGS human gastric adenocarcinoma cells via lentiviral mediated transduction of short-hairpin (sh) RNA targeting NET1. Knockdown was assessed using quantitative PCR. Cell proliferation was assessed using an MTS assay and cell migration was assessed using a wound healing scratch assay. Cell invasion was assessed using a transwell matrigel invasion assay. Gene expression profiles were examined using affymetrix oligonucleotide U133A expression arrays. A student's t test was used to determine changes of statistical significance.</p> <p>Results</p> <p>GC cells were transduced with NET1 shRNA resulting in a 97% reduction in NET1 mRNA (p < 0.0001). NET1 knockdown significantly reduced the invasion and migration of GC cells by 94% (p < 0.05) and 24% (p < 0.001) respectively, while cell proliferation was not significantly altered following NET1 knockdown. Microarray analysis was performed on non-target and knockdown cell lines, treated with and without 10 μM lysophosphatidic acid (LPA) allowing us to identify NET1-dependent, LPA-dependent and NET1-mediated LPA-induced gene transcription. Differential gene expression was confirmed by quantitative PCR. Shortlisted NET1-dependent genes included STAT1, TSPAN1, TGFBi and CCL5 all of which were downregulatd upon NET1 downregulation. Shortlisted LPA-dependent genes included EGFR and PPARD where EGFR was upregulated and PPARD was downregulated upon LPA stimulation. Shortlisted NET1 and LPA dependent genes included IGFR1 and PIP5K3. These LPA induced genes were downregulated in NET1 knockdown cells.</p> <p>Conclusions</p> <p>NET1 plays an important role in GC cell migration and invasion, key aspects of GC progression. Furthermore, the gene expression profile further elucidates the molecular mechanisms underpinning NET1-mediated aggressive GC cell behaviour.</p

Synergistic interaction effect between job control and social support at work on general psychological distress

Purpose Little is known about the interaction between job control and social support at work on common mental disorders. To examine whether there is a synergistic interaction effect between job control and social support at work on general psychological distress and whether it differs by the level of job demands. Methods About 1,940 male and female workers from the Malmo Shoulder and Neck Study were chosen for this cross-sectional study. Job control, social support at work, and job demands were measured by the Swedish version of the Job Content Questionnaire, and general psychological distress was assessed by the General Health Questionnaire. Results A significant excessive risk increase for general psychological distress was observed when workers had both low job control and low social support at work in both men and women. The synergistic effect was stronger in women, when job demands were low (Rothman's synergy index was 2.16 vs. 1.51 when job demands were high). However, in male workers, while a strong synergistic effect between job control and social support at work was found when job demands were low (synergy index was 9.25), there was an antagonistic effect when job demands were high (synergy index was 0.52). Conclusions There was a synergistic interaction effect between job control and social support at work on general psychological distress, but the synergistic effect or its effect size differed by the level of job demands and gender. An atomic, additive approach to the risk assessment of the psychosocial work characteristics on common mental disorders could be misleading or lead to a risk underestimation

Incomplete Inhibition of Sphingosine 1-Phosphate Lyase Modulates Immune System Function yet Prevents Early Lethality and Non-Lymphoid Lesions

BACKGROUND: S1PL is an aldehyde-lyase that irreversibly cleaves sphingosine 1-phosphate (S1P) in the terminal step of sphingolipid catabolism. Because S1P modulates a wide range of physiological processes, its concentration must be tightly regulated within both intracellular and extracellular environments. METHODOLOGY: In order to better understand the function of S1PL in this regulatory pathway, we assessed the in vivo effects of different levels of S1PL activity using knockout (KO) and humanized mouse models. PRINCIPAL FINDINGS: Our analysis showed that all S1PL-deficient genetic models in this study displayed lymphopenia, with sequestration of mature T cells in the thymus and lymph nodes. In addition to the lymphoid phenotypes, S1PL KO mice (S1PL(-/-)) also developed myeloid cell hyperplasia and significant lesions in the lung, heart, urinary tract, and bone, and had a markedly reduced life span. The humanized knock-in mice harboring one allele (S1PL(H/-)) or two alleles (S1PL(H/H)) of human S1PL expressed less than 10 and 20% of normal S1PL activity, respectively. This partial restoration of S1PL activity was sufficient to fully protect both humanized mouse lines from the lethal non-lymphoid lesions that developed in S1PL(-/-) mice, but failed to restore normal T-cell development and trafficking. Detailed analysis of T-cell compartments indicated that complete absence of S1PL affected both maturation/development and egress of mature T cells from the thymus, whereas low level S1PL activity affected T-cell egress more than differentiation. SIGNIFICANCE: These findings demonstrate that lymphocyte trafficking is particularly sensitive to variations in S1PL activity and suggest that there is a window in which partial inhibition of S1PL could produce therapeutic levels of immunosuppression without causing clinically significant S1P-related lesions in non-lymphoid target organs

Skeletal muscle overexpression of nicotinamide phosphoribosyl transferase in mice coupled with voluntary exercise augments exercise endurance

Objective: Nicotinamide phosphoribosyl transferase (NAMPT) is the rate-limiting enzyme in the salvage pathway that produces nicotinamide adenine dinucleotide (NAD+), an essential co-substrate regulating a myriad of signaling pathways. We produced a mouse that overexpressed NAMPT in skeletal muscle (NamptTg) and hypothesized that NamptTg mice would have increased oxidative capacity, endurance performance, and mitochondrial gene expression, and would be rescued from metabolic abnormalities that developed with high fat diet (HFD) feeding. Methods: Insulin sensitivity (hyperinsulinemic-euglycemic clamp) was assessed in NamptTg and WT mice fed very high fat diet (VHFD, 60% by kcal) or chow diet (CD). The aerobic capacity (VO2max) and endurance performance of NamptTg and WT mice before and after 7 weeks of voluntary exercise training (running wheel in home cage) or sedentary conditions (no running wheel) were measured. Skeletal muscle mitochondrial gene expression was also measured in exercised and sedentary mice and in mice fed HFD (45% by kcal) or low fat diet (LFD, 10% by kcal). Results: NAMPT enzyme activity in skeletal muscle was 7-fold higher in NamptTg mice versus WT mice. There was a concomitant 1.6-fold elevation of skeletal muscle NAD+. NamptTg mice fed VHFD were partially protected against body weight gain, but not against insulin resistance. Notably, voluntary exercise training elicited a 3-fold higher exercise endurance in NamptTg versus WT mice. Mitochondrial gene expression was higher in NamptTg mice compared to WT mice, especially when fed HFD. Mitochondrial gene expression was higher in exercised NamptTg mice than in sedentary WT mice. Conclusions: Our studies have unveiled a fascinating interaction between elevated NAMPT activity in skeletal muscle and voluntary exercise that was manifest as a striking improvement in exercise endurance