Interleukin-6 Contributes to Inflammation and Remodeling in a Model of Adenosine Mediated Lung Injury

Chronic lung diseases are the third leading cause of death in the United States due in part to an incomplete understanding of pathways that govern the progressive tissue remodeling that occurs in these disorders. Adenosine is elevated in the lungs of animal models and humans with chronic lung disease where it promotes air-space destruction and fibrosis. Adenosine signaling increases the production of the pro-fibrotic cytokine interleukin-6 (IL-6). Based on these observations, we hypothesized that IL-6 signaling contributes to tissue destruction and remodeling in a model of chronic lung disease where adenosine levels are elevated.We tested this hypothesis by neutralizing or genetically removing IL-6 in adenosine deaminase (ADA)-deficient mice that develop adenosine dependent pulmonary inflammation and remodeling. Results demonstrated that both pharmacologic blockade and genetic removal of IL-6 attenuated pulmonary inflammation, remodeling and fibrosis in this model. The pursuit of mechanisms involved revealed adenosine and IL-6 dependent activation of STAT-3 in airway epithelial cells.These findings demonstrate that adenosine enhances IL-6 signaling pathways to promote aspects of chronic lung disease. This suggests that blocking IL-6 signaling during chronic stages of disease may provide benefit in halting remodeling processes such as fibrosis and air-space destruction

P1 receptors and cytokine secretion

Evidence has accumulated in the last three decades to suggest tissue protection and regeneration by adenosine in multiple different cell types. Adenosine produced in hypoxic or inflamed environments reduces tissue injury and promotes repair by receptor-mediated mechanisms. Among other actions, regulation of cytokine production and secretion by immune cells, astrocytes and microglia (the brain immunocytes) has emerged as a main mechanism at the basis of adenosine effects in diseases characterized by a marked inflammatory component. Many recent studies have highlighted that signalling through A1 and A2A adenosine receptors can powerfully prevent the release of pro-inflammatory cytokines, thus inhibiting inflammation and reperfusion injury. However, the activation of adenosine receptors is not invariably protective of tissues, as signalling through the A2B adenosine receptor has been linked to pro-inflammatory actions which are, at least in part, mediated by increased release of pro-inflammatory cytokines from epithelial cells, astrocytes and fibroblasts. Here, we discuss the multiple actions of P1 receptors on cytokine secretion, by analyzing, in particular, the role of the various adenosine receptor subtypes, the complex reciprocal interplay between the adenosine and the cytokine systems, their pathophysiological significance and the potential of adenosine receptor ligands as new anti-inflammatory agents

Purinergic signalling links mechanical breath profile and alveolar mechanics with the pro-inflammatory innate immune response causing ventilation-induced lung injury

Severe pulmonary infection or vigorous cyclic deformation of the alveolar epithelial type I (AT I) cells by mechanical ventilation leads to massive extracellular ATP release. High levels of extracellular ATP saturate the ATP hydrolysis enzymes CD39 and CD73 resulting in persistent high ATP levels despite the conversion to adenosine. Above a certain level, extracellular ATP molecules act as danger-associated molecular patterns (DAMPs) and activate the pro-inflammatory response of the innate immunity through purinergic receptors on the surface of the immune cells. This results in lung tissue inflammation, capillary leakage, interstitial and alveolar oedema and lung injury reducing the production of surfactant by the damaged AT II cells and deactivating the surfactant function by the concomitant extravasated serum proteins through capillary leakage followed by a substantial increase in alveolar surface tension and alveolar collapse. The resulting inhomogeneous ventilation of the lungs is an important mechanism in the development of ventilation-induced lung injury. The high levels of extracellular ATP and the upregulation of ecto-enzymes and soluble enzymes that hydrolyse ATP to adenosine (CD39 and CD73) increase the extracellular adenosine levels that inhibit the innate and adaptive immune responses rendering the host susceptible to infection by invading microorganisms. Moreover, high levels of extracellular adenosine increase the expression, the production and the activation of pro-fibrotic proteins (such as TGF-β, α-SMA, etc.) followed by the establishment of lung fibrosis

Systemic sclerosis in Sarawak : a profile of patients trated in the Sarawak General Hospital

We performed a cross-sectional study of the demography, clinical and laboratory features of patients with systemic sclerosis patients followed up in our centre from 1984 to 2007. There were 23 cases with the majority of them (96%) being female. They have a mean age of 50.3 years and a mean disease duration of 6.02 (SD 5.82) years. Our patients comprised of multi-ethnic groups with predominantly Chinese (52%), Sarawak natives (35%) and Malays (13%). They have a mean lag time to diagnosis of 24.8 (SD 34.8) months. All the patients have sclerodermatous skin changes with 16(70%) having diffuse scleroderma and 7(30%) having limited scleroderma. The common clinical manifestations found in our patients were Raynaud’s phenomenon (91%), sclerodactyly (65%), digital ulcers (52%) and pulmonary fibrosis (52%). There was low incidence of pulmonary hypertension (13%) and renal involvement (4%). The majority of our patients (67%) have positive ANA with 33% positive Scl-70. The majority received calcium channel blockers (87%), aspirin (48%) and low-dose prednisolone (48%). One patient developed adenocarcinoma of the lung on follow-up. This study demonstrated the rarity of systemic sclerosis in our centre with considerable lag time to diagnosis in our patients. Diffuse cutaneous systemic scleroderma is more common in our centre with rare pulmonary hypertension and renal involvement

Cytotoxic drug use in treatment of dogs and cats with cancer by UK veterinary practices (2003 to 2004)

Objectives: To describe the range and frequency of cytotoxic drugs prescribed within UK veterinary practices to treat dogs and cats with cancer, determine the effect of practice demographic variables on this practice and determine the frequency with which intravenous catheters were used during administration of parenteral cytotoxic drugs. Methods: A postal survey of 1838 veterinary practices providing care for dogs and cats within the UK. Results: Prescription of cytotoxic drugs to treat dogs and cats with cancer during the preceding 12 months was reported by 70·8 per cent practices. The most widely prescribed agents were cyclophosphamide (65·4 per cent) and vincristine (63·5 per cent). Twenty-three per cent of responding practices had prescribed an antitumour antibiotic and 8·3 per cent had prescribed a platinum agent. The median frequency of prescription was between once a month and once every three months. Increasing frequency and range of cytotoxic drug prescription were associated with practice employment of higher numbers of veterinary surgeons and increased levels of pet insurance among practice clients. Almost a quarter of practices administering vesicant parenteral cytotoxic drugs failed to always use intravenous catheters to do so. Clinical Significance: Prescription of cytotoxic drugs, and therefore the potential for occupational exposure of staff, was widespread among UK veterinary practices providing care for dogs and cats