Procalcitonin--a marker and mediator of inflammation

Evaluation of procalcitonin levels is a sensitive investigation which is significant for differentiation between microbial and non-microbial infection, a determination of its dynamics and a prediction of therapy results. It is, however, necessary to evaluate its levels in relation to other investigations and their dynamics (other inflammatory markers, organ function dynamics), which specify diagnosis with the clinical condition of a patient. Even today, 10 years after the discovery of procalcitonin as an inflammatory marker and likely mediator of a cytokine cascade, there are many unanswered questions regarding its production in relation to physiological significance during the defensive response of an organism (12). Boucher formulated a simple conclusion in 2000: Procalcitonin should not be seen as the marker of sepsis but as one of many potentially useful markers.     

Heat shock protein 60 as a mediator of adipose tissue inflammation and insulin resistance

The stress protein heat shock protein 60 (Hsp60) induces secretion of proinflammatory mediators from murine adipocytes. This study aimed to study Hsp60 as a mediator of adipose tissue inflammation and skeletal muscle cell (SkMC) insulin sensitivity and to quantify plasma Hsp60 concentrations in lean and obese individuals. Regulation of Hsp60 release and Hsp60-induced cytokine secretion and signaling was measured in human adipocytes and SkMCs. Adipocytes exhibited higher Hsp60 release than preadipocytes and SkMCs, which was further stimulated by cytokines and Toll-like receptor (TLR)-4 activation. Hsp60 activated extracellular signal-related kinase (ERK)-1/2, Jun NH(2)-terminal kinase (JNK), p38, nuclear factor (NF)-κB, and impaired insulin-stimulated Akt phosphorylation in adipocytes. Furthermore, Hsp60 stimulated adipocytes to secrete tumor necrosis factor-α, interleukin (IL)-6, and IL-8. In SkMCs, Hsp60 activated ERK1/2, JNK, and NF-κB and inhibits insulin signaling and insulin-stimulated glucose uptake. SkMCs released IL-6, IL-8, and monocyte chemoattractant protein-1 on Hsp60 stimulation. Plasma Hsp60 was higher in obese males than in lean males and correlated positively with BMI, blood pressure, leptin, and homeostasis model assessment-insulin resistance. In summary, Hsp60 is released by human adipocytes, increased in plasma of obese humans, and induces insulin resistance. This is accompanied by activation of proinflammatory signaling in human adipocytes and SkMCs. Thus, Hsp60 might be a factor underlying adipose tissue inflammation and obesity-associated metabolic disorders.     

Uric acid as a mediator of endothelial dysfunction, inflammation, and vascular disease

Recent experimental findings have led to renewed interest in the possible role of uric acid in the pathogenesis of both hypertension and vascular disease. Often considered an antioxidant, biochemical and in vitro data indicate that noncrystalline, soluble uric acid also can react to form radicals, increase lipid oxidation, and induce various pro-oxidant effects in vascular cells. In vitro and in vivo findings suggest that uric acid may contribute to endothelial dysfunction by inducing antiproliferative effects on endothelium and impairing nitric oxide production. Proinflammatory and proliferative effects of soluble uric acid have been described on vascular smooth muscle cells (VSMCs), and in animal models of mild hyperuricemia, hypertension develops in association with intrarenal vascular disease. Possible adverse effects of uric acid on the vasculature have been linked to increased chemokine and cytokine expression, induction of the renin-angiotensin system, and to increased vascular C-reactive protein (CRP) expression. Experimental evidence suggests a complex but potentially direct causal role for uric acid in the pathogenesis of hypertension and atherosclerosis.     

Insulin activation of phosphatidylinositol 3-kinase in the hypothalamic arcuate nucleus: a key mediator of insulin-induced anorexia

In peripheral tissues, insulin signaling involves activation of the insulin receptor substrate (IRS)-phosphatidylinositol 3-kinase (PI3K) enzyme system. In the hypothalamus, insulin functions with leptin as an afferent adiposity signal important for the regulation of body fat stores and hepatic glucose metabolism. To test the hypothesis that hypothalamic insulin action involves intracellular PI3K signaling, we used histochemical and biochemical methods to determine the effect of insulin on hypothalamic IRS-PI3K activity. Here, we report that insulin induces tyrosine phosphorylation of the insulin receptor and IRS-1 and -2, increases binding of activated IRS-1 and -2 to the regulatory subunit of PI3K, and activates protein kinase B/Akt, a downstream target of PI3K. Using an immunohistochemical technique to detect PI 3,4,5-triphosphate, the main product of PI3K activity, we further demonstrate that in the arcuate nucleus, insulin-induced PI3K activity occurs preferentially within cells that contain IRS-2. Finally, we show that the food intake- lowering effects of insulin are reversed by intracerebroventricular infusion of either of two PI3K inhibitors at doses that have no independent feeding effects. These findings support the hypothesis that the IRS-PI3K pathway is a mediator of insulin action in the arcuate nucleus and, combined with recent evidence that leptin activates PI3K signaling in the hypothalamus, provide a plausible mechanism for neuronal cross-talk between insulin and leptin signaling.     

Activated caspase-1 is not a central mediator of inflammation in the course of ischemia-reperfusion

BACKGROUND: Upon transplantation, donor organs subjected to prolonged ischemia suffer from reperfusion injury. Recent observations suggest that caspase activation is involved in inducing the deleterious inflammatory reaction that mediates reperfusion injury. Release of cytokines like interleukin (IL)-1 and IL-18 may occur during apoptosis through activation of caspase-1/IL-1beta-converting enzyme. We hypothesized that caspase-1 activation is a key event in apoptosis/ caspase-dependent inflammation during the development of renal reperfusion injury. METHODS: Caspase-1-/-, caspase-1+/+ as well as Swiss mice were subjected to 45 min of renal ischemia and 24 hr of reperfusion. Animals were administered agents capable of neutralizing the pro-inflammatory activation products of caspase-1 (IL-1 receptor antagonist, anti-IL-1 receptor antibody, and anti-IL-18 antibody). The extent of renal functional deterioration, inflammation, and apoptosis were compared. RESULTS: No improvement in renal function as reflected by serum ureum and creatinine were found in caspase-1-/- mice as compared to wild type controls. Caspase-1-/- mice showed slightly attenuated renal inflammation as indicated by decreased renal neutrophil influx, but failed to show changes in intrarenal tumor necrosis factor-alpha production. Moreover, caspase-1-/- mice clearly exhibited reperfusion-induced apoptosis as reflected by renal terminal deoxynucleotidyltransferase histology and internucleosomal DNA cleavage. Treatment with IL-1 receptor antagonist, anti-IL-1 receptor antibody, or anti-IL-18 antibody minimally reduced renal functional deterioration, inflammation, and apoptosis. CONCLUSIONS: These findings suggest that activated caspase-1 and its inflammatory products are involved in, but not crucial to, the induction of inflammation after renal ischemia-reperfusion. Hence, apart from caspase-1, other (combinations of) activated caspases are likely to be more prominently involved in renal reperfusion injury.     

Interleukin-6--a key mediator of systemic and local symptoms in rheumatoid arthritis

Interleukin-6 (IL-6) is a pleiotropic cytokine, present at elevated levels in patients with rheumatoid arthritis (RA). Il-6 signaling involves both a specific IL-6 receptor (IL-6R) and a ubiquitous signal-transducing protein, gp130 that is also utilized by other members of the IL-6 family. Il-6 signaling occurs by two mechanisms. Conventional signaling involves the binding of IL-6 to transmembrane IL-6R on cells expressing this receptor. In contrast, trans-signaling involves binding between the complex of soluble IL-6R/IL-6 and membrane-bound gp130. Trans-signaling allows IL-6 to affect cells that do not express IL-6R, including many synovial cells. The biological activities of IL-6 contribute to both systemic and local RA symptoms. Il-6 is a strong inducer of the acute-phase response, which can result in fever, secondary amyloidosis, anemia, and elevations in acute-phase proteins, such as C-reactive protein (CRP). The ability of IL-6 to induce B-cell differentiation may lead to the formation of rheumatoid factor and other autoantibodies. In joints, IL-6 promotes osteoclast activation and induces the release of matrix metalloproteinases, thus contributing to joint damage. In patients with RA, IL-6 levels correlate with markers of disease activity and clinical symptoms, and animal studies support the concept that this cytokine plays a role in the development of inflammatory arthritis. Clinical trials with tocilizumab, a humanized monoclonal antibody to soluble IL-6R, have shown that blocking IL-6 signaling reduces RA symptoms and markers of disease activity. Current evidence thus strongly supports the association between IL-6 and RA symptoms and suggests that IL-6 blockade will be a useful therapeutic strategy for patients with this disease.     

Hypoxia--a key regulator of angiogenesis and inflammation in rheumatoid arthritis

The importance of inflammation in rheumatoid arthritis (RA) is well understood. This knowledge has resulted in the development of anti-inflammatory therapies--either broadly acting (such as steroids) or more specific approaches (such as antibodies against TNF)--with biologic therapies (including TNF inhibitors) revolutionizing the treatment of RA. However, what is less well appreciated in RA are the links between inflammation, blood-vessel formation (angiogenesis) and cellular responses to changes in oxygen tension. Inadequate oxygenation, termed hypoxia, is thought to drive the increase in synovial angiogenesis that occurs in RA, through expression of hypoxia-inducible molecules, including vascular endothelial growth factor (VEGF). This process promotes further infiltration of inflammatory cells and production of inflammatory mediators, perpetuating synovitis. This Review highlights the molecular pathways activated by hypoxia, and how these pathways might interact with inflammatory signaling to promote and maintain synovitis in RA, with a particular focus on the response of macrophages to hypoxia in the context of RA. Successful treatment of RA, for example with anti-TNF antibodies, reduces levels of proangiogenic factors, including VEGF, and leads to normalization of the vasculature. These processes emphasise the close links between hypoxia, angiogenesis and inflammation in this disease and supports the concept that angiogenesis blockade could be of therapeutic benefit in RA.     

Interleukin-6 in the injured patient. Marker of injury or mediator of inflammation?

OBJECTIVE: The effects of interleukin (IL)-6 in the injured patient are examined in an attempt to clarify the potential pathophysiologic role of IL-6 in the response to injury. SUMMARY BACKGROUND DATA: Interleukin-6 is an integral cytokine mediator of the acute phase response to injury and infection. However, prolonged and excessive elevations of circulating IL-6 levels in patients after trauma, burns, and elective surgery have been associated with complications and mortality. The mechanistic role of IL-6 in mediating these effects is unclear. METHODS: A review of current literature is performed to summarize the origins, mechanisms of action, and biologic effects of IL-6 and to characterize the IL-6 response to injury. RESULTS: Interleukin-6 is a multifunctional cytokine expressed by a variety of cells after a multitude of stimuli, under complex regulatory control mechanisms. The IL-6 response to injury is uniquely consistent and related to the magnitude of the insult. Moreover, the early postinjury IL-6 response correlates with complications as well as mortality. CONCLUSIONS: Interleukin-6 appears to play an active role in the postinjury immune response, making it an attractive therapeutic target in attempts to control hyperinflammatory provoked organ injury.     

炎症是脂质异常介导的动脉粥样硬化和肾脏损害的中心环节

动脉粥样硬化的本质是血管壁的慢性炎症。长期的慢性微炎症状态可以加速血管的动脉粥样硬化过程。肾小球硬化与动脉粥样硬化在病理改变和病理生理机制上很相似，因此过去的许多临床和动物实验的研究已经证明，脂质失调是导致肾病进展和肾小球硬化的重要因素。而近年来国内外的最新研究更进一步证实炎症影响细胞水平的胆固醇稳态是加速脂质介导的动脉粥样硬化和肾脏损害的关键。     

术后认知功能障碍的炎症机制

背景 术后认知功能障碍(postoperative cognitive dysfunction,POCD)是老年患者手术后常见的中枢神经系统并发症.目前POCD的发病机制尚不清楚.POCD的发生影响了患者术后恢复,延长了住院时间,增加了术后并发症的发生率和死亡率;对家庭及社会造成严重的经济负担,POCD将成为一个严重的社会问题.目的 旨在推进POCD的研究,使得这一严重问题得到解决.内容 以往的研究表明,麻醉、手术可能是的POCD主要原因,而老龄则是惟一明确的危险应素,提示中枢神经系统退行性改变与POCD的发生可能有着重要联系,而麻醉和手术加重了这种退行性改变所致的认知功能衰退.趋向 较多研究表明炎症反应在与衰老有关的认知功能减退中起着重要作用,而手术创伤和应激引起的炎症反应是围术期发生的重要病理生理学改变.近年来炎症反应在POCD发生中的作用备受关注,现对POCD发生中炎症反应方面的研究进展进行综述.