The role of peptide leukotrienes in renal failure induced by a tourniquet

Protective effects of a potent c5a receptor antagonist on experimental acute limb ischemia-reperfusion in rats

OBJECTIVES

The capacity of a potent C5a receptor antagonist to inhibit various parameters of local and remote organ injury following lower limb ischemia-reperfusion (I/R) in rats was investigated.

METHODS

Rats were subjected to 2 h bilateral hindlimb ischemia and 4 h reperfusion. Drug-treated rats received AcF-[OPdChaWR] (1 mg/kg) iv either 10 min before ischemia or 10 min prior to reperfusion, or orally (10 mg/kg) 30 min prior to ischemia. Levels of circulating creatine kinase (CK), lactate dehydrogenase (LDH), alanine and aspartate aminotransferase (ALT/AST), creatinine, blood urea nitrogen (BUN), polymorphonuclear leukocytes (PMNs), and calcium (Ca(++)) and potassium (K(+)) ions were determined. Other parameters measured included urinary protein levels, muscle edema, and myeloperoxidase (MPO) concentrations in the lung, liver, and muscle along with liver homogenate tumor necrosis factor-alpha (TNF-alpha) concentrations.L RESULTS: imb I/R injury was characterized by significant elevations of CK, LDH, ALT, AST, creatinine, BUN, proteinuria, PMNs, serum K(+), muscle edema, organ MPO, and liver homogenate TNF-alpha concentrations, but a significant reduction in serum Ca(2+) concentrations. When rats were treated with AcF-[OPdChaWR], there were significant improvements in all these parameters.

CONCLUSIONS

These results indicate a pivotal role for C5a in inducing local and remote organ injury and suggest a possible new drug therapeutic category for preventing anticipated tissue injury associated with I/R.

The gene expression of cytokines and chemokines induced by tourniquet shock in mice

Traumatic shock is one of the major fields in forensic pathology, but its mechanism remains elusive from the pathophysiological aspects. Tourniquet shock has been established as one of the animal models of traumatic shock, and we examined the gene expression of cytokines and chemokines in the lung and liver in tourniquet shock using mice. Tourniquet was conducted by the application of elastic bands with five turns at both the thighs as high as possible for 2 h, followed by reperfusion. In this procedure, more than 90% mice died within 48 h after reperfusion. Serum hepatic transaminase and hematocrit values significantly increased at 2 h after reperfusion, and their elevation was still evident after 10 h. Histopathologically, hemorrhages, congestion and leukocyte recruitment were observed in the lung and liver specimens after 6 h of reperfusion. Immunohistochemical analysis with anti-myeloperoxidase antibody demonstrated a massive neutrophil infiltration in the lung and liver at 2 h or more after reperfusion. RT-PCR analyses demonstrated that the gene expression of interleukin-1beta, tumor necrosis factor-alpha, monocytes chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-2, KC and vascular endothelial adhesion molecule-1 was most enhanced in the lung and liver at 2 h after reperfusion. Thus, the gene expression of cytokines and chemokines is presumed to be closely related with the onset of tourniquet shock. From the forensic aspects, these cytokines and chemokines are considered to be useful markers for the early diagnosis of tourniquet shock.

Adverse renal effects of anti-inflammatory agents: evaluation of selective and nonselective cyclooxygenase inhibitors

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs), i.e. nonselective cyclooxygenase COX inhibitors have well-documented nephrotoxicity. Adverse renal effects occur because of inhibition of the synthesis of cyclooxygenase-derived prostaglandins which act to modulate pathologic processes that would normally impair various renal functions. The introduction of the selective COX-2 inhibitors raised hope that this class of drugs would reduce injury in both the gastrointestinal tract and the kidneys. Animal and human data, however, suggest that COX-2 synthesized prostaglandins are important in the modulation of renal physiology during adverse conditions. Hence, it appears that these drugs are equal in causing nephrotoxicity as the nonselective COX inhibitors.

[Pneumatic tourniquets in orthopedics]

Pneumatic tourniquets, often used to provide a bloodless operating field, carry a risk of adverse effects. Limb exsanguination by gravitation is less aggressive than by mechanical means. Skin, muscles, nerves and vessels suffer maximally under tourniquet because of mechanical pressure, with both a sagittal force, responsible for compression and an axial force responsible for stretchening. All parts of the limb are therefore affected by ischaemia. The restarting of circulation will also increase lesions at the microcirculatory level, responsible for the "no reflow" phenomena. Transient reperfusion intervals are not necessarily beneficial. These effects will significantly contribute to the post tourniquet sensory motor injuries. The tourniquet increases the risk of sepsis. Tourniquet release allows metabolites from the leg to enter into the circulation, and also carries a risk of pulmonary thromboembolism. Carbon dioxide is eliminated by spontaneous hyperventilation under regional anaesthesia. If not eliminated by an increase of mechanical ventilation during general anaesthesia, it may raise intracranial pressure in head trauma patients. Various chemotactic and cytolytic agents may cause lung injury. Mobilization of blood volume at tourniquet placement and release may have detrimental haemodynamic effects in patients with coronary or cardiac insufficiency. The tourniquet increases arterial pressure after 20 to 25 minutes under general anaesthesia. Regional anaesthesia is considered as the technique of choice for the prevention of "tourniquet hypertension", closely linked to pain and relievable by local anaesthetics. Tourniquet modifies also the pharmacokinetics of anaesthetic and other agents. It generates hyperthermia, especially in children. Prospective and comparative studies did not show any advantage as far as duration of surgery and amount of blood loss are concerned. In order to minimize its side effects, the tourniquet must be used within the frame of a strict procedure, with a well adapted and regularly checked equipment. Duration of ischaemia should be as short as possible and not continue for more than two hours, with a reperfusion of 15 minutes every hour. Local hypothermia seems to be a safe means for decreasing side effects.

Protective effect of peptide leukotriene antagonist on renal failure induced by a tourniquet in rabbits

We studied the effects of a selective antagonist of peptide leukotriene D4/E4 (LY-171883) and 5-lipoxygenase inhibitor diethylcarbamazine (DEC) in renal failure induced by a tourniquet, because peptide leukotrienes (LTs) were suggested to play a key role in our previous study. The hind limbs of anesthetized rabbits were fastened for 5 h and then released for 6 h. LY171883 (4 mg/kg/h) and DEC (40 mg/kg/h) were administered via the aural vein from 30 min before the tourniquet and during the experiment in each tourniquet group. The tourniquet induced renal injuries represented by increases in serum BUN and creatinine, and the injuries in the fastened muscles represented increases in serum CPK and edema index of the fastened site. LY171883 and DEC significantly attenuated the aggravation of the renal functions induced by a tourniquet when compared with the vehicle-treated group. LY171883 did not affect the injuries in the fastened muscles, but DEC attenuated it significantly when compared with the vehicle-treated group. The protection of peptide LT antagonist and 5-lipoxygenase inhibitor in the tourniquet-induced renal failure elucidate that peptide LTs trigger renal failure induced by a tourniquet.