Nadja Scherbakov

Endogenous Tumor Necrosis Factor α (TNFα) Requires TNF Receptor Type 2 to Generate Heat Hyperalgesia in a Mouse Cancer Model

To provide a tool to investigate the mechanisms inducing and maintaining cancer-related pain and hyperalgesia, a soft tissue tumor/metastasis model was developed that is applicable in C57BL/6J wild-type and transgenic mice. We show that the experimental tumor-induced heat hyperalgesia and nociceptor sensitization were prevented by systemic treatment with the tumor necrosis factor α (TNFα) antagonist etanercept. In naive mice, exogenous TNFα evoked heat hyperalgesia in vivo and sensitized nociceptive nerve fibers to heat in vitro. TNFα enhanced the expression of the nociceptor-specific heat transducer ion channel transient receptor potential vanilloid 1 (TRPV1) and increased the amplitudes of capsaicin and heat-activated ionic currents via p38/MAP (mitogen-activated protein) kinase and PKC (protein kinase C). Deletion of the tumor necrosis factor receptor type 2 (TNFR2) gene attenuated heat hyperalgesia and prevented TRPV1 upregulation in tumor-bearing mice, whereas TNFR1 gene deletion played a minor role. We propose endogenous TNFα as a key player in cancer-related heat hyperalgesia and nociceptor sensitization that generates TRPV1 upregulation and sensitization via TNFR2.

A Key Role for gp130 Expressed on Peripheral Sensory Nerves in Pathological Pain

Interleukin-6 (IL-6) is a key mediator of inflammation. Inhibitors of IL-6 or of its signal transducing receptor gp130 constitute a novel class of anti-inflammatory drugs, which raise great hopes for improved treatments of painful inflammatory diseases such as rheumatoid arthritis. IL-6 and gp130 may enhance pain not only indirectly through their proinflammatory actions but also through a direct action on nociceptors (i.e., on neurons activated by painful stimuli). We found indeed that the IL-6/gp130 ligand-receptor complex induced heat hypersensitivity both in vitro and in vivo. This process was mediated by activation of PKC-δ via Gab1/2/PI3K and subsequent regulation of TRPV1, a member of the transient receptor potential (TRP) family of ion channels. To assess the relevance of this direct pain promoting effect of IL-6, we generated conditional knock-out mice, which lack gp130 specifically in nociceptors, and tested them in models of inflammatory and tumor-induced pain. These mice showed significantly reduced levels of inflammatory and tumor-induced pain but no changes in immune reactions or tumor growth. Our results uncover the significance of gp130 expressed in peripheral pain sensing neurons in the pathophysiology of major clinical pain disorders and suggest their use as novel pain relieving agents in inflammatory and tumor pain.

Body Weight After Stroke Lessons From the Obesity Paradox

Background and Purpose— Outcome after acute stroke is determined to a large extent by poststroke complications. Nutritional status and metabolic balance may substantially contribute to outcome after stroke. Key mechanisms of stroke pathophysiology can induce systemic catabolic imbalance with impaired metabolic efficiency and degradation of body tissues. Summary— Tissue wasting, sarcopenia, and cachexia may impair and delay poststroke rehabilitation and worsen the prognosis. Although current guidelines for secondary prevention after stroke recommend weight reduction, increasing evidence suggests that patients who are overweight and mildly obese may actually have a better outcome. An “obesity paradox” has been identified to describe the contrasting impact of being overweight in patients with chronic illness compared with healthy populations. We present an overview on the metabolic regulation in patients with stroke and evaluate current data on the impact of body weight and weight change after stroke. The emerging picture suggests that being overweight and obese may impact patients with stroke differently than it does healthy subjects. Conclusions— We propose that current knowledge on obesity and its management in primary prevention cannot be transferred to patients with established stroke. Systematic studies on changes in body composition after stroke and on treatment options are warranted to establish the pathophysiology and evidence-driven management of nutritional status in these patients.

Stroke induced Sarcopenia: Muscle wasting and disability after stroke

Stroke is the second leading cause of death and the leading cause of disability in Western countries. More than 60% of patients remain disabled, 50% of patients suffer from hemiparesis and 30% remain unable to walk without assistance. The skeletal muscle is the main effector organ accountable for disability in stroke. This disability is primarily attributed to the brain lesion; however less attention is paid to structural, metabolic and functional alterations of muscle tissue after stroke. Hemiparetic stroke leads to various muscle abnormalities: A combination of denervation, disuse, inflammation, remodelling and spasticity accounts for a complex pattern of muscle tissue phenotype change and atrophy. The molecular mechanisms of muscle degradation after stroke are only incompletely understood. Reinnervation, fibre-type shift, disuse atrophy, and local inflammatory activation are only some of the key features yet to be explained. Only limited data is available today on clinical muscle changes after stroke that results from few studies in a mere 500 patients. Despite its importance for optimum post stroke recovery, stroke-related sarcopenia is not considered in current guidelines for stroke therapy or rehabilitation and measurement tools to address sarcopenia are infrequently used. This lack of robust evidence on muscle pathology after stroke and on treatment strategies needs to be addressed in an interdisciplinary integrated approach. This review provides an overview on current pathophysiologic insights and on clinical relevance of sarcopenia in stroke patients and on measurement tools to address the problem in the clinical setting.

Sarcopenia in stroke—facts and numbers on muscle loss accounting for disability after stroke

Stroke is the third leading cause of death and the leading cause of disability in Western countries. More than 60% of patients remain disabled, 50% of patients suffer from some hemiparesis and 30% remain unable to walk without assistance. The skeletal muscle is the main effector organ accountable for disability in stroke. This disability is, however, traditionally attributed to the brain injury itself and less attention is paid to structural, metabolic and functional aspects of muscle tissue. Hemiparetic stroke leads to various muscle abnormalities. A combination of denervation, disuse, inflammation, remodelling and spasticity account for a complex pattern of muscle tissue phenotype change and atrophy. While the molecular mechanisms of muscle degradation after stroke are only incompletely understood, a stroke-related sarcopenia may be concluded. Reinnervation, fiber-type shift, disuse atrophy and local inflammatory activation are only some of the key features to be addressed. Despite the importance for optimum post stroke recovery, stroke-related sarcopenia is not recognised in current guidelines for stroke therapy and rehabilitation. A total of not more than 500 patients forms the basis for all available evidence on clinical muscle changes after stroke. A lack of robust evidence on muscle pathology after stroke and on treatment strategies becomes apparent that needs to be addressed in an interdisciplinary integrated approach.

Intestinal congestion and right ventricular dysfunction: a link with appetite loss, inflammation, and cachexia in chronic heart failure

AIMS Mechanisms leading to cachexia in heart failure (HF) are not fully understood. We evaluated signs of intestinal congestion in patients with chronic HF and their relationship with cachexia. METHODS AND RESULTS Of the 165 prospectively enrolled outpatients with left ventricular ejection fraction ≤40%, 29 (18%) were cachectic. Among echocardiographic parameters, the combination of right ventricular dysfunction and elevated right atrial pressure (RAP) provided the best discrimination between cachectic and non-cachectic patients [area under the curve 0.892, 95% confidence interval (CI): 0.832-0.936]. Cachectic patients, compared with non-cachectic, had higher prevalence of postprandial fullness, appetite loss, and abdominal discomfort. Abdominal ultrasound showed a larger bowel wall thickness (BWT) in the entire colon and terminal ileum in cachectic than in non-cachectic patients. Bowel wall thickness correlated positively with gastrointestinal symptoms, high-sensitivity C-reactive protein, RAP, and truncal fat-free mass, the latter serving as a marker of the fluid content. Logistic regression analysis showed that BWT was associated with cachexia, even after adjusting for cardiac function, inflammation, and stages of HF (odds ratio 1.4, 95% CI: 1.0-1.8; P-value = 0.03). Among the cardiac parameters, only RAP remained significantly associated with cachexia after multivariable adjustment. CONCLUSION Cardiac cachexia was associated with intestinal congestion irrespective of HF stage and cardiac function. Gastrointestinal discomfort, appetite loss, and pro-inflammatory activation provide probable mechanisms, by which intestinal congestion may trigger cardiac cachexia. However, our results are preliminary and larger studies are needed to clarify the intrinsic nature of this relationship.

Stroke-related sarcopenia: specific characteristics.

Sarcopenia is characterized by muscle wasting and is primarily a disease of the elderly. A stroke-specific sarcopenia has been described recently. Stroke-related sarcopenia has a number of features that distinguish it from the age-related sarcopenia. The disability from stroke depends on the brain lesion leading to impairment of the efferent neuronal pathways. However, the alterations of structural and functional muscle capacity are secondary and depend rather on complex pathophysiological reactions including imbalanced efferent neurovegetative control, systemic and local metabolic imbalance, feeding difficulties, and inflammation. Muscle structural changes start to develop within hours after stroke, followed by rapid reduction of muscle mass. The pathophysiological mechanisms leading to the muscle mass decline are still not understood in details. This review provides insights into the specific features of the stroke-related sarcopenia. Recent research achievements in this area and clinical implications will be discussed.

TRPC channels and diacylglycerol dependent calcium signaling in rat sensory neurons.

Transient receptor potential (TRP) channels of the TRPV, TRPA, and TRPM subfamilies play important roles in somatosensation including nociception. While particularly the Thermo TRPs have been extensively investigated in sensory neurons, the relevance of the subclass of “canonical” TRPC channels in primary afferents is yet elusive. In the present study, we investigated the presence and contribution to Ca2+ transients of TRPC channels in dorsal root ganglion neurons. We found that six of the seven known TRPC subtypes were expressed in lumbar DRG, with TRPC1, C3, and C6 being the most abundant. Microfluorimetric calcium measurements showed Ca2+ influx induced by oleylacylglycerol (OAG), an activator of the TRPC3/C6/C7 subgroup. Furthermore, OAG induced rises in [Ca2+]i were inhibited by SKF96365, an inhibitor of receptor and store operated calcium channel. OAG induced calcium transients were also inhibited by blockers of diacylglycerol (DAG) lipase, lipoxygenase or cyclooxygenase and, intriguingly, by inhibitors of the capsaicin receptor TRPV1. Notably, SKF96365 did not affect capsaicin-induced calcium transients. Taken together, our findings suggest that TRPC are functionally expressed in subpopulations of DRG neurons. These channels, along with TRPV1, contribute to calcium homeostasis in rat sensory neurons.

The impact of iron deficiency and anaemia on exercise capacity and outcomes in patients with chronic heart failure. Results from the Studies Investigating Co-morbidities Aggravating Heart Failure.

UNLABELLED Anaemia and iron deficiency (ID) are important co-morbidities in patients with chronic heart failure (HF) and both may lead to reduced exercise capacity. METHODS We enrolled 331 out-patients with stable chronic HF (mean age: 64 ± 11 years, 17% female, left ventricular ejection fraction [LVEF] 35 ± 13%, body mass index [BMI] 28.5 ± 5.2 kg/m(2), New York Heart Association [NYHA] class 2.2 ± 0.7, chronic kidney disease 35%, glomerular filtration rate 61.7 ± 20.1 mL/min). Anaemia was defined according to World Health Organization criteria (haemoglobin [Hb] < 13 g/dL in men, < 12 g/dL in women). ID was defined as serum ferritin < 100 μg/L or ferritin < 300 μg/L with transferrin saturation (TSAT) < 20%. Exercise capacity was assessed as peak oxygen consumption (peak VO2) by spiroergometry and 6-minute walk test (6MWT). RESULTS A total of 91 (27%) patients died from any cause during a mean follow-up of 18 months. At baseline, 98 (30%) patients presented with anaemia and 149 (45%) patients presented with ID. We observed a significant reduction in exercise capacity in parallel to decreasing Hb levels (r = 0.24, p < 0.001). In patients with anaemia and ID (n = 63, 19%), exercise capacity was significantly lower than in patients with ID or anaemia only. Cox regression analysis showed that after adjusting for NYHA, age, hsCRP and creatinine anaemia is an independent predictor of mortality in patients with HF (hazard ratio [HR]: 0.56, 95% confidence interval [CI]: 0.33-0.97, p = 0.04). CONCLUSION The impact of anaemia on reduced exercise capacity and on mortality is stronger than that of ID. Anaemia remained an independent predictor of death after adjusting for clinically relevant variables.

Detection of muscle wasting in patients with chronic heart failure using C-terminal agrin fragment: results from the Studies Investigating Co-morbidities Aggravating Heart Failure (SICA-HF).

Skeletal muscle wasting affects 20% of patients with chronic heart failure and has serious implications for their activities of daily living. Assessment of muscle wasting is technically challenging. C‐terminal agrin‐fragment (CAF), a breakdown product of the synaptically located protein agrin, has shown early promise as biomarker of muscle wasting. We sought to investigate the diagnostic properties of CAF in muscle wasting among patients with heart failure.