FK 506 reduces the injury experienced following renal ischemia and reperfusion

Targeting Inflammation and Oxidative Stress as a Therapy for Ischemic Kidney Injury

Inflammation and oxidative stress are the main pathological processes that accompany ischemic injury of kidneys and other organs. Based on this, these factors are often chosen as a target for treatment of acute kidney injury (AKI) in a variety of experimental and clinical studies. Note, that since these two components are closely interrelated during AKI development, substances that treat one of the processes often affect the other. The review considers several groups of promising nephroprotectors that have both anti-inflammatory and antioxidant effects. For example, many antioxidants, such as vitamins, polyphenolic compounds, and mitochondria-targeted antioxidants, not only reduce production of the reactive oxygen species in the cell but also modulate activity of the immune cells. On the other hand, immunosuppressors and non-steroidal anti-inflammatory drugs that primarily affect inflammation also reduce oxidative stress under some conditions. Another group of therapeutics is represented by hormones, such as estrogens and melatonin, which significantly reduce severity of the kidney damage through modulation of both these processes. We conclude that drugs with combined anti-inflammatory and antioxidant capacities are the most promising agents for the treatment of acute ischemic kidney injury.

Effects of tacrolimus and dexamethasone on tubulointerstitial fibrosis in mercuric chloride treated Brown Norway rats

We investigated the effects of daily injection of tacrolimus (FK), an immunosuppressor, or dexamethasone (Dx), an antiinflammatory agent, on renal tubulointerstitial fibrosis in mercuric chloride-treated Brown Norway rats. The tubular lesions observed after one time injection of mercuric chloride were reduced in FK-treatment group, but not in Dx-treatment group. Moreover, FK reduced infiltration of mononuclear cells, especially macrophages, and proliferation of myofibroblasts in renal intestitium and also inhibited renal interstitial fibrosis through the reduction of the expressions of fibrosis-related factors, i.e. plasminogen activator inhibitor-1 and transforming growth factor-beta1. On the other hand, Dx reduced lymphocyte infiltraton, but did not inhibit macrophage infiltration. In addition, Dx did not suppress myofibroblast profiferation, upregulation of fibrosis-related factors, and interstitial fibrosis. From these findings, it is suggested that FK may inhibit renal interstitial fibrosis through inhibition of macrophage infiltration, and that macrophages and myofibroblasts are very important fibrogenic factors in the development of mercuric chloride-induced renal tubulointerstitial fibrosis in BN rats.

Role of TNF in mediating renal insufficiency following cardiac surgery: evidence of a postbypass cardiorenal syndrome

Recent evidence has implicated proinflammatory mediators such as TNF-alpha in the pathophysiology of ischemia-reperfusion (I/R) injury. Clinically, serum levels of TNF-alpha are increased after myocardial infarction and after cardiopulmonary bypass. Both cardiopulmonary bypass and renal ischemia-reperfusion injury induce a cascade of events leading to cellular damage and organ dysfunction. Tumor necrosis factor (TNF), a potent proinflammatory cytokine, is released from both the heart and the kidney in response to ischemia and reperfusion. TNF released during cardiopulmonary bypass induces glomerular fibrin deposition, cellular infiltration, and vasoconstriction, leading to a reduction in glomerular filtration rate (GFR). The signaling cascade through which renal ischemia-reperfusion induces TNF production is beginning to be elucidated. Oxidants released following reperfusion activate p38 mitogen-activated protein kinase (p38 MAP kinase) and the TNF transcription factor, NFkappaB, leading to subsequent TNF synthesis. In a positive feedback, proinflammatory fashion, binding of TNF to specific TNF membrane receptors can reactivate NFkappaB. This provides a mechanism by which TNF can upregulate its own expression as well as facilitate the expression of other genes pivotal to the inflammatory response. Following its production and release, TNF results in both renal and myocardial apoptosis and dysfunction. An understanding of these mechanisms may allow the adjuvant use of anti-TNF therapeutic strategies in the treatment of renal injury. The purposes of this review are: (1) to evaluate the evidence which indicates that TNF is produced by the heart following cardiopulmonary bypass; (2) to examine the effect of TNF on myocardial performance; (3) to outline the mechanisms by which the kidney produces significant TNF in response to ischemia and reperfusion; (5) to investigate the role of TNF in renal ischemia-reperfusion injury, (6) to describe the mechanisms of TNF-induced renal cell apoptosis, and (7) to suggest potential anti-TNF strategies designed to reduce renal insufficiency following cardiac surgery.

Modulating the functions of neutrophils and lipid peroxidation by FK506 in a rat model of thermal injury

Neutrophils diffusely invade lung, liver, kidney, intestine, muscle and burned skin following burn injury. To ameliorate this invasion and minimize its effects, neutrophils can be modulated by giving neutrophil inhibitors and modulators. In this study, FK506 was used to decrease neutrophil infiltration and lipid peroxidation in remote organs (lung, liver, kidney and intestine) in a burned rat model. FK506 is a new major immunosuppressive agent that is known to modulate neutrophils during inflammation. Neutrophil infiltration was assessed indirectly by measuring myeloperoxidase (MPO) activity biochemically in remote organs following 30% full thickness burn injury. Malondialdehyde (MDA), the end product of lipid peroxidation, was measured biochemically in remote organs and plasma to determine if there is a relationship between neutrophil infiltration and lipid peroxidation after burn injury. FK506 was given intramuscularly at the dose of 0.5 and 1.0 mg/kg for three days before burn injury. Thermal trauma to the skin caused a statistically significant increase in MPO activity and MDA content in remote organs. FK506 was effective in reducing lipid peroxidation and neutrophil infiltration especially at 24 h postinjury in lung, liver and kidney. FK506 may have some benefit (prophylactic) in reducing systemic neutrophilic injury and related lipid peroxidation in burns.

Renal ischaemia--reperfusion injury

Ischaemia-reperfusion injury is a complex interrelated sequence of events that classically involves the vascular endothelium and activated leucocytes. During the ischaemic phase the endothelium is primed both to produce free radicals and to secrete chemoattractants. The resultant neutrophil sequestration serves to amplify the injury, but damage is not confined to the postischaemic area and more generalized effects typically follow. The situation in the kidney is complex for, while ischaemia primes the tissue for reperfusion damage, it also causes early and irreversible tubular injury. Furthermore, it appears that relatively less importance should be attached to the involvement of neutrophils than at other sites, and relatively more to a local postischaemic imbalance in the levels of nitric oxide and endothelin. Despite a greater understanding of the pathogenesis of ischaemia-reperfusion injury, effective treatment remains elusive and research is hampered by apparent species and organ-specific differences.

Tacrolimus. A review of its pharmacology, and therapeutic potential in hepatic and renal transplantation

Tacrolimus (FK 506) is a macrolide immunosuppressant which possesses similar but more potent immunosuppressant properties compared with cyclosporin, inhibiting cell-mediated and humoral immune responses. Like cyclosporin, tacrolimus demonstrates considerable interindividual variation in its pharmacokinetic profile. This has caused difficulty in defining the optimum dosage regimen and has highlighted the usefulness of therapeutic drug monitoring. Most clinical studies with tacrolimus have neither been published in their entirety nor subjected to extensive peer review; there is also a paucity of published randomised investigations of tacrolimus versus cyclosporin, particularly in renal transplantation. Despite these drawbacks, tacrolimus has shown notable efficacy as a rescue or primary immunosuppressant therapy when combined with corticosteroids in adult and paediatric recipients following liver or kidney transplantation. Indeed, graft salvage rates in patients experiencing rejection or drug-related toxicity were > or = 50%, although data in renal transplantation are limited. Compared with cyclosporin as a primary immunosuppressant, tacrolimus showed comparable or greater patient/graft survival rates in liver allograft recipients (where cost savings associated with reduced hospitalisation costs were evident in one study), and comparable patient/graft survival in patients following kidney transplantation. Worthy of note was the efficacy of tacrolimus as a primary immunosuppressant in patients who received en bloc kidney allografts. The incidence of rejection was largely reduced following rescue therapy with tacrolimus and was generally lower (notably for refractory rejection) than that observed for cyclosporin, at least in liver allograft recipients. This was reflected in less need for adjunct immunotherapy including antilymphocyte preparations for the treatment of rejection episodes. The potential for reduction or withdrawal of corticosteroid therapy with tacrolimus appears to be a distinct advantage compared with cyclosporin, and this may be enhanced by the reduced incidence of infectious complications and of hypertension and hypercholesterolaemia reported by some investigators. In other respects, however, the tolerability profile of tacrolimus appears to be broadly similar to that of cyclosporin. Against this background, preliminary data indicate that tacrolimus provides a valuable therapeutic alternative to retransplantation in patients experiencing liver or kidney graft rejection or drug-related toxicity. Pending confirmation of initial randomised studies and preliminary results from large randomised investigations, tacrolimus may well be considered as an alternative primary immunosuppressant to cyclosporin in hepatic (particularly) and renal transplantation. Furthermore, the steroid-sparing effects of tacrolimus, although of benefit to all patient groups, may prove to be of particular worth in children and in en bloc kidney recipients. In these patients tacrolimus may well emerge as the drug of choice.(ABSTRACT TRUNCATED AT 400 WORDS)