Retraction：Dietary Supplementation of L-Carnosine Prevents Ischemia/Reperfusion-Induced Renal Injury in Rats

Carnosine alleviates podocyte injury in diabetic nephropathy by targeting caspase-1-mediated pyroptosis

Diabetic nephropathy (DN) is a main complication of diabetes and often develops into end-stage nephropathy. Histologically, DN progresses as the gradual loss of podocytes with the loss of glomerular podocytes being the earliest sign of DN. Pyroptosis is a new type of programmed cell death and has been mechanistically correlated with podocyte injury in DN. The current study aimed to evaluate the protective effects of carnosine on glomerular podocytes in DN, both in vivo and in vitro. Using high glucose-treated cultured MPC5 cells and a streptozotocin (STZ)-induced diabetic mouse model, we evaluated the effects of carnosine on alleviating podocyte injury in DN. We found that carnosine significantly reversed albuminuria and histopathological lesions and alleviated renal inflammatory and pyroptosis responses in STZ-induced diabetic mice for 12 weeks. The results also showed that carnosine strongly inhibited podocyte inflammation and podocyte pyroptosis in vitro. Cellular Thermal Shift Assay (CETSA) and molecular docking results revealed that mechnaistically caspase-1 was the target of carnosine. We then found that silencing caspase-1 eliminated the protective effect of carnosine. Interestingly, we also found that caspase-1 and gasdermin D expression were increased in renal biopsy tissue of patients with DN. Our study is the first to demonstrate the novel role of carnosine in alleviating podocyte injury by inhibiting pyroptosis via the targeting of caspase-1. Carnosine may have potential as a therapeutic agent in treating DN by targeting caspase-1.

Carnosine and Kidney Diseases: What We Currently Know?

Carnosine (beta-alanyl-L-histidine) is an endogenously synthesised dipeptide which is present in different human tissues e.g. in the kidney. Carnosine is degraded by enzyme serum carnosinase, encoding by CNDP1 gene. Carnosine is engaged in different metabolic pathways in the kidney. It reduces the level of proinflammatory and profibrotic cytokines, inhibits advanced glycation end products' formation, moreover, it also decreases the mesangial cell proliferation. Carnosine may also serve as a scavenger of peroxyl and hydroxyl radicals and a natural angiotensin-converting enzyme inhibitor. This review summarizes the results of experimental and human studies concerning the role of carnosine in kidney diseases, particularly in chronic kidney disease, ischemia/reperfusion-induced acute renal failure, diabetic nephropathy and also drug-induced nephrotoxicity. The interplay between serum carnosine concentration and serum carnosinase activity and polymorphism in the CNDP1 gene is discussed. Carnosine has renoprotective properties. It has a promising potential for the treatment and prevention of different kidney diseases, particularly chronic kidney disease which is a global public health issue. Further studies of the role of carnosine in the kidney may offer innovative and effective strategies for the management of kidney diseases.

Synthesis of radioiodinated carnosine for hepatotoxicity imaging induced by carbon tetrachloride and its biological assessment in rats

The imaging of organs is very important in the field of diagnosis especially in case of liver diseases. In the present work, carnosine was successfully labeled with iodine-131 at room temperature in acidic medium using chloramine-T (Ch-T) as moderate oxidizing agent. The parameters affecting labeling of carnosine such as amount of oxidizing agent, amount of substrate, pH value of the reaction mixture, reaction temperature and reaction time, were investigated. The best conditions for formation of 131I-carnosine (131I-CAR) complex were 40 μg of chloramine-T (Ch-T), 75 μg of carnosine, pH 4 and 45 min reaction time at room temperature. The radiochemical yield for 131I-CAR complex was (91 ± 0.11) % at optimum conditions and the labeled complex was stable for 2 h after labeling process. Biodistribution study was achieved using three groups of rats (normal, treated by inactive carnosine and hepatotoxicity rats induced by CCl4). Hepatotoxicity of liver was evaluated using different biochemical markers such as ALT, AST and ALK.P. The 131I-CAR complex showed selective bio-localization in stomach and liver and its selectivity increases in acquired hepatotoxicity. The biological distribution indicates that the suitability of 131I-CAR as a potential hepatotoxicity imaging to detect hepatitis and medical prognosis.

Dexmedetomidine on renal ischemia-reperfusion injury in rats: assessment by means of NGAL and histology

BACKGROUND

Ischemic acute kidney injury is a common occurrence in the perioperative period and in critical patients admitted to intensive care units. The reestablishment of blood supply may worsen injury through the ischemia-reperfusion (I/R) mechanism. We investigated the effect of dexmedetomidine on the kidneys of rats subjected to an experimental I/R model.

METHODS

34 rats anesthetized with isoflurane was undergone right nephrectomy and randomly assigned to four groups: Control C (saline solution); Dexmedetomidine D (dexmedetomidine); Sham S (saline solution); Sham with Dexmedetomidine SD (dexmedetomidine). The serum levels of neutrophil gelatinase-associated lipocalin (NGAL) were measured at time-points T1 (following stabilization), T2 (ischemia), T3 (reperfusion), T4 (12 h after of I/R). The kidneys were subjected to histological examination.

RESULTS

The NGAL levels were significantly higher at T4 compared with T1. Upon histological examination, the left kidneys in groups C and D exhibited a similar extent of cell injury.

CONCLUSION

The levels of NGAL did not indicate either protection against or worsening of kidney injury. Histological examination for acute tubular necrosis showed that dexmedetomidine did not protect the kidneys from I/R.

Physiology and pathophysiology of carnosine

Carnosine (β-alanyl-l-histidine) was discovered in 1900 as an abundant non-protein nitrogen-containing compound of meat. The dipeptide is not only found in skeletal muscle, but also in other excitable tissues. Most animals, except humans, also possess a methylated variant of carnosine, either anserine or ophidine/balenine, collectively called the histidine-containing dipeptides. This review aims to decipher the physiological roles of carnosine, based on its biochemical properties. The latter include pH-buffering, metal-ion chelation, and antioxidant capacity as well as the capacity to protect against formation of advanced glycation and lipoxidation end-products. For these reasons, the therapeutic potential of carnosine supplementation has been tested in numerous diseases in which ischemic or oxidative stress are involved. For several pathologies, such as diabetes and its complications, ocular disease, aging, and neurological disorders, promising preclinical and clinical results have been obtained. Also the pathophysiological relevance of serum carnosinase, the enzyme actively degrading carnosine into l-histidine and β-alanine, is discussed. The carnosine system has evolved as a pluripotent solution to a number of homeostatic challenges. l-Histidine, and more specifically its imidazole moiety, appears to be the prime bioactive component, whereas β-alanine is mainly regulating the synthesis of the dipeptide. This paper summarizes a century of scientific exploration on the (patho)physiological role of carnosine and related compounds. However, far more experiments in the fields of physiology and related disciplines (biology, pharmacology, genetics, molecular biology, etc.) are required to gain a full understanding of the function and applications of this intriguing molecule.

The protective effects of carnosine in alcohol-induced hepatic injury in rats

Consumption of alcohol leads to oxidative stress in liver by inducing lipid peroxidation. The aim of this study was to investigate the effects of carnosine (CAR) in alcohol-induced liver injury by biochemical and histomorphological evaluations. The rats were divided into four groups, namely, control group, alcohol (AL) group, CAR group and AL + CAR group. Three doses of ethanol (5 g/kg, 25% (v/v) in distilled water) were given by nasogastric catheter for twice-a-day. CAR (100 mg/kg) was given 1 h before the administration of ethanol using the same method. Levels of alanine aminotransferase, aspartate aminotransferase, myeloperoxidase and malondialdehyde were significantly increased in the AL group compared with control, CAR and AL + CAR groups. Glutathione level was significantly decreased in the AL group, while it was increased in the AL + CAR group. Immunoreactivity of caspase-3 and bax increased in the hepatocytes of AL group when compared with control and AL + CAR groups. Expression of bcl-2 was decreased in AL group than AL + CAR group. Under electron microscopy, dense mitochondria, accumulation of lipid, sinusoidal dilatation, vacuolization and decrease in the number of microvilli were observed in AL group, while these findings were markedly less in the AL + CAR group. In conclusion, pretreatment of CAR is effective for recovering biochemical alterations and morphologic damage in the liver of rats treated with ethanol.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Carnosine prevents apoptosis of glomerular cells and podocyte loss in STZ diabetic rats

BACKGROUND/AIMS

We identified carnosinase-1 (CN-1) as risk-factor for diabetic nephropathy (DN). Carnosine, the substrate for CN-1, supposedly is a protective factor regarding diabetic complications. In this study, we hypothesized that carnosine administration to diabetic rats might protect the kidneys from glomerular apoptosis and podocyte loss.

METHODS

We examined the effect of oral L-carnosine administration (1g/kg BW per day) on apoptosis, podocyte loss, oxidative stress, AGEs and hexosamine pathway in kidneys of streptozotocin-induced diabetic Wistar rats after 3 months of diabetes and treatment.

RESULTS

Hyperglycemia significantly reduced endogenous kidney carnosine levels. In parallel, podocyte numbers significantly decreased (-21% compared to non-diabetics, p<0.05), apoptotic glomerular cells numbers increased (32%, compared to non-diabetic, p<0.05) and protein levels of bax and cytochrome c increased (175% and 117%). Carnosine treatment restored carnosine kidney levels, prevented podocytes loss (+23% compared to diabetic, p<0.05), restrained glomerular apoptosis (-34% compared to diabetic; p<0.05) and reduced expression of bax and cytochrome c (-63% and -54% compared to diabetics, both p<0.05). In kidneys of all diabetic animals, levels of ROS, AGEs and GlcNAc-modified proteins were increased.

CONCLUSION

By inhibition of pro-apoptotic signaling and independent of biochemical abnormalities, carnosine protects diabetic rat kidneys from apoptosis and podocyte loss.

New concept in nutrition for the maintenance of the aging eye redox regulation and therapeutic treatment of cataract disease; synergism of natural antioxidant imidazole-containing amino acid-based compounds, chaperone, and glutathione boosting agents: a systemic perspective on aging and longevity emerged from studies in humans

Cataract, opacification of the lens, is one of the commonest causes of loss of useful vision during aging, with an estimated 16 million people world-wide affected. The role of nutritional supplementation in prevention of onset or progression of ocular disease is of interest to health care professionals and patients. The aging eye seems to be at considerable risk from oxidative stress. This review outlines the potential role of the new nutritional strategy on redox balance in age-related eye diseases and detail how the synergism and interaction of imidazole-containing amino acid-based compounds (nonhydrolized L-carnosine, histidine), chaperone agents (such as, L-carnosine, D-pantethine), glutathione-boosting agents (N-acetylcysteine, vitamin E, methionine), and N-acetylcarnosine eye drops plays key roles in the function and maintenance of the redox systems in the aging eye and in the treatment of human cataract disease. A novel patented oral health supplement is presented which enhances the anticataract activity of eye drops and activates functional visual acuity. The clinical data demonstrate the effectiveness and safety of a combined oral health care treatment with amino acids possessing chaperone-like activity with N-acetylcarnosine lubricant eye drops. L-carnosine and N-acetylcarnosine protected the chaperone activity of alpha-crystallin and reduced the increased posttranslational modifications of lens proteins. Biological activities of the nonhydrolyzed carnosine in the oral formulation are based on its antioxidant and antiglycating (transglycating) action that, in addition to heavy metal chelation and pH-buffering ability, makes carnosine an essential factor for preventing sight-threatening eye disorders having oxidative stress in their pathogenesis, neurodegeneration, and accumulation of senile features. The findings suggest that synergism is required between carnosine or other imidazole-containing compounds and reduced glutathione in tissues and cells for efficacious protection from protein carbonylation as a biomarker for the ability of the non-toxic compounds to reduce oxidative stress. Potential therapeutic applications of oral forms of nonhydrolized carnosine and their specific mechanisms to manage telomere attrition and vascular aging might help elderly patients to withstand the problems of sight-threatening eye diseases related to oxidative stress and accelerated biological ageing in linked with earlier onset of diseases.

The carbonyl scavenger carnosine ameliorates dyslipidaemia and renal function in Zucker obese rats

The metabolic syndrome is a risk factor that increases the risk for development of renal and vascular complications. This study addresses the effects of chronic administration of the endogenous dipeptide carnosine (β-alanyl-L-histidine, L-CAR) and of its enantiomer (β-alanyl-D-histidine, D-CAR) on hyperlipidaemia, hypertension, advanced glycation end products, advanced lipoxidation end products formation and development of nephropathy in the non-diabetic, Zucker obese rat. The Zucker rats received a daily dose of L-CAR or D-CAR (30 mg/kg in drinking water) for 24 weeks. Systolic blood pressure was recorded monthly. At the end of the treatment, plasma levels of triglycerides, total cholesterol, glucose, insulin, creatinine and urinary levels of total protein, albumin and creatinine were measured. Several indices of oxidative/carbonyl stress were also measured in plasma, urine and renal tissue. We found that both L- and D-CAR greatly reduced obese-related diseases in obese Zucker rat, by significantly restraining the development of dyslipidaemia, hypertension and renal injury, as demonstrated by both urinary parameters and electron microscopy examinations of renal tissue. Because the protective effect elicited by L- and D-CAR was almost superimposable, we conclude that the pharmacological action of L-CAR is not due to a pro-histaminic effect (D-CAR is not a precursor of histidine, since it is stable to peptidic hydrolysis), and prompted us to propose that some of the biological effects can be mediated by a direct carbonyl quenching mechanism.

Aging, Proteotoxicity, Mitochondria, Glycation, NAD and Carnosine: Possible Inter-Relationships and Resolution of the Oxygen Paradox

It is suggested that NAD(+) availability strongly affects cellular aging and organism lifespan: low NAD(+) availability increases intracellular levels of glycolytic triose phosphates (glyceraldehyde-3-phosphate and dihydroxyacetone-phosphate) which, if not further metabolized, decompose spontaneously into methylglyoxal (MG), a glycating agent and source of protein and mitochondrial dysfunction and reactive oxygen species (ROS). MG-damaged proteins and other aberrant polypeptides can induce ROS generation, promote mitochondrial dysfunction and inhibit proteasomal activity. Upregulation of mitogenesis and mitochondrial activity by increased aerobic exercise, or dietary manipulation, helps to maintain NAD(+)availability and thereby decreases MG-induced proteotoxicity. These proposals can explain the apparent paradox whereby aging is seemingly caused by increased ROS-mediated macromolecular damage but is ameliorated by increased aerobic activity. It is also suggested that increasing mitochondrial activity decreases ROS generation, while excess numbers of inactive mitochondria are deleterious due to increased ROS generation. The muscle- and brain-associated dipeptide, carnosine, is an intracellular buffer which can delay senescence in cultured human fibroblasts and delay aging in senescence-accelerated mice. Carnosine's ability to react with MG and possibly other deleterious carbonyl compounds, and scavenge various ROS, may account for its protective ability towards ischemia and ageing.

NAD+ availability and proteotoxicity

It has been shown that NAD(+) availability is important for neuronal survival following ischemia (Liu et al., Neuromolecular Med 11:28-42, 2009). It is proposed here that NAD(+) may also control proteotoxicity by influencing both formation and catabolism of altered proteins. It is suggested that low NAD(+) availability promotes synthesis of methylglyoxal (MG) which can induce formation of glycated proteins, ROS, and dysfunctional mitochondria. That glyoxalase overexpression and carnosine are both protective against MG and ischemic injury support this proposal. Recognition and elimination of altered proteins is enhanced by NAD(+) through effects on stress protein expression and autophagy.

Carnosine and its possible roles in nutrition and health

The dipeptide carnosine has been observed to exert antiaging activity at cellular and whole animal levels. This review discusses the possible mechanisms by which carnosine may exert antiaging action and considers whether the dipeptide could be beneficial to humans. Carnosine's possible biological activities include scavenger of reactive oxygen species (ROS) and reactive nitrogen species (RNS), chelator of zinc and copper ions, and antiglycating and anticross-linking activities. Carnosine's ability to react with deleterious aldehydes such as malondialdehyde, methylglyoxal, hydroxynonenal, and acetaldehyde may also contribute to its protective functions. Physiologically carnosine may help to suppress some secondary complications of diabetes, and the deleterious consequences of ischemic-reperfusion injury, most likely due to antioxidation and carbonyl-scavenging functions. Other, and much more speculative, possible functions of carnosine considered include transglutaminase inhibition, stimulation of proteolysis mediated via effects on proteasome activity or induction of protease and stress-protein gene expression, upregulation of corticosteroid synthesis, stimulation of protein repair, and effects on ADP-ribose metabolism associated with sirtuin and poly-ADP-ribose polymerase (PARP) activities. Evidence for carnosine's possible protective action against secondary diabetic complications, neurodegeneration, cancer, and other age-related pathologies is briefly discussed.

Transport mechanisms of carnosine in SKPT cells: contribution of apical and basolateral membrane transporters

PURPOSE

The aim of this study was to investigate the transport properties of carnosine in kidney using SKPT cell cultures as a model of proximal tubular transport, and to isolate the functional activities of renal apical and basolateral transporters in this process.

METHODS

The membrane transport kinetics of 10 microM [3H]carnosine was studied in SKPT cells as a function of time, pH, potential inhibitors and substrate concentration. A cellular compartment model was constructed in which the influx, efflux and transepithelial clearances of carnosine were determined. Peptide transporter expression was probed by RT-PCR.

RESULTS

Carnosine uptake was 15-fold greater from the apical than basolateral surface of SKPT cells. However, the apical-to-basolateral transepithelial transport of carnosine was severely rate-limited by its cellular efflux across the basolateral membrane. The high-affinity, proton-dependence, concentration-dependence and inhibitor specificity of carnosine supports the contention that PEPT2 is responsible for its apical uptake. In contrast, the basolateral transporter is saturable, inhibited by PEPT2 substrates but non-concentrative, thereby, suggesting a facilitative carrier.

CONCLUSIONS

Carnosine is expected to have a substantial cellular accumulation in kidney but minimal tubular reabsorption in blood because of its high influx clearance across apical membranes by PEPT2 and very low efflux clearance across basolateral membranes.

The protective effects of carnosine and melatonin in ischemia-reperfusion injury in the rat liver

The reperfusion following liver ischemia results in hepatocyte damage and apoptosis. The aim of this study was to investigate the effects of two antioxidant agents, carnosine and melatonin, in rat liver ischemia-reperfusion injury. Five study groups were formed; I. sham, II. ischemia-reperfusion, III. ischemia-reperfusion+melatonin, IV. ischemia-reperfusion+carnosine, V. ischemia-reperfusion+melatonin+carnosine. Then 250 mg/kg carnosine and 10 mg/kg melatonin were administered intraperitoneally 30 min before ischemia and immediately after the reperfusion. Sinusoidal dilatation, congestion and neutrophil infiltration were observed in the ischemia-reperfusion group while these symptoms were less pronounced in the treatment groups. Alanine aminotransferase, aspartate aminotransferase and myeloperoxidase levels were increased in the ischemia-reperfusion group while they were lowered in the treatment groups. Glutathione level was low in the ischemia-reperfusion group while it tended to increase in the ischemia-reperfusion+carnosine administered and ischemia-reperfusion+carnosine+melatonin administered groups. There was an increase in the number of apoptotic cells in the ischemia-reperfusion group while this number was lowered in the treatment groups. Carnosine was more effective than melatonin in the reversal of structural and biochemical alterations that resulted from ischemia-reperfusion injury. The administration of melatonin and carnosine together yielded better outcomes compared to the sole administration of each agent.

Carnosine attenuates mast cell degranulation and histamine release induced by oxygen-glucose deprivation

Carnosine (beta-alanyl-histidine) is a naturally occurring dipeptide that has been characterized as a putative hydrophilic antioxidant. The protective function of carnosine has been demonstrated in neuronal cells under ischemic injury. The purpose of this study was to investigate the effects of carnosine on oxygen-glucose deprivation (OGD)-induced degranulation and histamine release from mast cells. Cultured mast cells were exposed to OGD for 4 h, and then the degranulation was observed immediately by microscopy. Histamine release was analyzed by high-performance liquid chromatography (HPLC). OGD caused degranulation of mast cells, and increased histamine and lactate dehydrogenase (LDH) release. Carnosine (at a concentration of 5 mM) alone did not produce any appreciable effect on degranulation, histamine, and LDH release from mast cells under normal condition, but significantly inhibited the degranulation, histamine, and LDH release of mast cells induced by OGD. These results indicate that carnosine can protect mast cells from degranulation and histamine release and it may be an endogenous mast cell stabilizer in the pathological processes induced by ischemia.

Protective effect of carnosine against cisplatin-induced nephrotoxicity in mice

The nephroprotective effect of the natural antioxidant carnosine was evaluated in mice with cisplatin-induced acute renal damage, in which generation of reactive oxygen species plays a major role. Nephrotoxicity was induced by a single i.p. injection of cisplatin (20mg/kg). Carnosine was administered for six consecutive days in a dose of 10mg/kg/day, i.p., starting 3 days before cisplatin injection. The results revealed that carnosine treatment significantly reduced blood urea nitrogen and serum creatinine levels elevated by cisplatin administration. Also, carnosine significantly attenuated cisplatin-induced increase in malondialdehyde and decrease in reduced glutathione, and catalase and superoxide dismutase activities in renal cortical homogenates. Additionally, histopathological examination and scoring showed that carnosine markedly ameliorated cisplatin-induced renal tubular necrosis. In conclusion, carnosine can be considered a feasible candidate to protect against nephrotoxicity commonly encountered with cisplatin treatment.

The hepatoprotective effect of carnosine against ischemia/reperfusion liver injury in rats

The potential protective effect of the natural antioxidant, carnosine was evaluated against ischemia/reperfusion liver injury in rats. Ischemia was induced by clamping the pedicle supplying the left hepatic lobe for 60 min followed by reperfusion for 2 h. Untreated rats exposed to ischemia/reperfusion showed significant elevation of serum aspartate aminotransferase and alanine aminotransferase levels, and malondialdehyde level and caspase-3 activity in liver homogenates associated with significant reduction in hepatic nitrite level, catalase and glutathione peroxidase activities as compared with sham-operated group. Pre-treatment with a single i.p. dose of carnosine (250 mg/kg), 30 min prior to the ischemic episode significantly attenuated the deterioration in the measured biochemical parameters observed with ischemia/reperfusion-induced liver injury. Also, light and electron microscopic examinations in ischemia/reperfusion untreated group revealed severe hepatic damage, such as cytoplasmic vacuolation, necrotic and apoptotic cell death, which was markedly ameliorated by pre-ischemic treatment with carnosine. These results strongly emphasize that carnosine can be useful as a prophylactic treatment to protect the liver against hypoxia-reoxygenation damage.

Intervention strategies to inhibit protein carbonylation by lipoxidation-derived reactive carbonyls

Protein carbonylation induced by reactive carbonyl species (RCS) generated by peroxidation of polyunsaturated fatty acids plays a significant role in the etiology and/or progression of several human diseases, such as cardiovascular (e.g., atherosclerosis, long-term complications of diabetes) and neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease, and cerebral ischemia). Most of the biological effects of intermediate RCS, mainly alpha,beta-unsaturated aldehydes, di-aldehydes, and keto-aldehydes, are due to their capacity to react with the nucleophilic sites of proteins, forming advanced lipoxidation end-products (ALEs). Because of the emerging deleterious role of RCS/protein adducts in several human diseases, different potential therapeutic strategies have been developed in the last few years. This review sheds focus on fundamental studies on lipid-derived RCS generation, their biological effects, and their reactivity with proteins, with particular emphasis to 4-hydroxy-trans-2-nonenal (HNE)-, acrolein (ACR)-, malondialdehyde (MDA)-, and glyoxal (GO)-modified proteins. It also discusses the recently developed pharmacological approaches for the management of chronic diseases in which oxidative stress and RCS formation are massively involved. Inhibition of ALE formation, based on carbonyl-sequestering agents, seems to be the most promising pharmacological tool and is reviewed in detail.

Effect of sevoflurane preconditioning on ischaemia/reperfusion injury in the rat kidney in vivo

BACKGROUND AND OBJECTIVE

Whereas the protective effect of anaesthetic and ischaemic preconditioning has been described for several organs, it is uncertain whether this mechanism is also effective in the kidney. We compared the effect of preconditioning with sevoflurane and preconditioning with short episodes of ischaemia on renal ischaemia/reperfusion injury in the rat in vivo.

METHODS

Fourteen days after right-sided nephrectomy, anaesthetized male Wistar rats were randomly assigned to a sham-operated group (no arterial occlusion, n = 5) or underwent 45 min of left renal artery occlusion (control group, n = 9) followed by 3 days of reperfusion. Two further experimental groups of animals were preconditioned prior to ischaemia either by administering 1 MAC sevoflurane for 15 min followed by 10 min of washout (sevoflurane group, n = 10) or by subjecting the animals to three short episodes of renal ischaemia (ischaemia-preconditioned group, n = 8). Blood creatinine was measured during reperfusion and morphological damage was assessed by histological examination.

RESULTS

Baseline creatinine values were similar in all four groups (0.7 +/- 0.2 mg dL-1; mean +/- SD) and remained unchanged in the sham-operated animals after 3 days (0.8 +/- 0.2 mg dL-1). Creatinine levels increased in the ischaemic preconditioning group (3.3 +/- 1.2 mg dL-1) and sevoflurane preconditioning group (4.0 +/- 1.1 mg dL-1) compared to the control group (1.6 +/- 0.6 mg dL-1). Morphological damage was less severe in the control group, i.e. in animals without preconditioning, than in both preconditioning groups.

CONCLUSION

Neither sevoflurane nor ischaemic preconditioning preserves renal function or attenuates cell damage in the rat in vivo.

Augmentation of Intrarenal Angiotensin II Levels in Uninephrectomized Aldosterone/Salt-Treated Hypertensive Rats; Renoprotective Effects of an Ultrahigh Dose of Olmesartan

Recent studies have suggested that aldosterone plays a role in the pathogenesis of renal injury. In this study, we investigated whether local angiotensin II (Ang II) activity contributes to the progression of renal injury in aldosterone/salt-induced hypertensive rats. Uninephrectomized rats were treated with 1% NaCl in a drinking solution and one of the following combinations for 6 weeks: vehicle (2% ethanol, s.c.; n=9), aldosterone (0.75 mug/h, s.c.; n=8), aldosterone+Ang II type 1 receptor blocker olmesartan (10 mg/kg/day, p.o.; n=8), or aldosterone+olmesartan (100 mg/kg/day, p.o.; n=9). Aldosterone/salt-treated hypertensive rats exhibited severe proteinuria and renal injury characterized by glomerular sclerosis and tubulointerstitial fibrosis. Aldosterone/salt-induced renal injury was associated with augmented expression of angiotensin converting enzyme and Ang II levels in the renal cortex and medullary tissues. Renal cortical and medullary mRNA expression of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) as well as the collagen contents were increased in aldosterone/salt-treated hypertensive rats. Treatment with olmesartan (10 or 100 mg/kg/day) had no effect on blood pressure but attenuated proteinuria in a dose-dependent manner. Olmesartan at 10 mg/kg/day tended to decrease renal cortical and medullary Ang II levels, TGF-beta and CTGF expression, and collagen contents; however, these changes were not significant. On the other hand, an ultrahigh dose of olmesartan (100 mg/kg/day) significantly decreased these values and ameliorated renal injury. These data suggest that augmented local Ang II activity contributes, at least partially, to the progression of aldosterone/salt-dependent renal injury.

Interactions between Carnosine and Captopril on Free Radical Scavenging Activity and Angiotensin-converting Enzyme Activity in vitro

Interactions between carnosine (beta-alanyl-L-histidine), being plentiful in skeletal muscles and neuronal tissues, and captopril, a widely used angiotensin-converting enzyme (ACE) inhibitor, were examined concerning free radical scavenging activity and ACE activity in vitro. Not only captopril, but also carnosine, at concentrations less than those ordinarily found in muscles and neuronal tissues, significantly scavenged 2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonate) (ABTS) radical cations, and inhibited ACE activity. Cupric ions reversed the ABTS scavenging activity of carnosine and captopril, whereas cupric ions strengthened the inhibitory action of carnosine on ACE activity. In contrast, cupric ions antagonized the inhibition of ACE activity induced by ethylenediaminetetraacetic acid, indicating that the inhibitory effect of carnosine on ACE activity is not related to the chelating action of carnosine. On the other hand, carnosine and captopril synergistically enhanced the free radical scavenging activity, but not the inhibitory effect on the ACE activity. These data suggest that carnosine in its concurrent use with captopril could act as a beneficial free radical scavenger, with less danger of overdose, in the inhibition of ACE activity.

Preventive Effect of Flavangenol on Ischemia/Reperfusion-Induced Acute Renal Failure in Rats

The effects of flavangenol on ischemia/reperfusion-induced acute renal failure (ARF) in rats were examined. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal functional parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow, urinary osmolality and fractional excretion of sodium were measured. Renal function in ARF rats markedly decreased at 1 d after reperfusion. Pre-ischemic treatment with flavangenol (3-30 mg/kg, i.v.) attenuated the ischemia/reperfusion-induced renal dysfunction. Histopathological examination of the kidney of ARF rats revealed severe renal damage, such as tubular necrosis and proteinaceous casts in tubuli, which were also significantly suppressed by the administration of flavangenol. These findings suggest that flavangenol supplementation may be a promising candidate for treatments to improve the ischemia/reperfusion-induced renal injury.