Hypoxic pre-conditioning in a rat renal ischemia model: an evaluation of the use of hydralazine

Hyper-Interleukin-6 Protects Against Renal Ischemic-Reperfusion Injury-A Mouse Model

Background: Most of the ischemia-reperfusion injury (IR-I) occurs during reperfusion and is mediated by the immune system. In this study we determined whether immunomodulation with hyper-Interleukin-6 (a recombinant designer cytokine composed of interleukin-6 linked to its soluble receptor) is protective against IR-I in mice kidneys.

Methods: Hyper-Interleukin-6 (HIL-6) was administered by in vivo plasmid DNA transfection to 10 male mice. Twenty-four hours later, unilateral nephrectomy was done. IR-I immediately followed by closure of the remaining kidney vascular pedicle for 40 min. Seven mice transfected with non-coding control plasmid served as the control group. The functional and morphological effects of IR-I and its effect on mice longevity were explored. This was done by serial blood tests and by histopathology done upon sacrifice of the animals at post-operative day 7.

Findings: Mice pretreated with HIL-6 had a mean creatinine level at post-operative day 1 of 35.45 ± 4.03 μmol/l and mean Urea level was 14.18 ± 2.69 mmol/l, whereas mean creatinine was 89.33 ± 69.27 μmol/l (P = 0.025), and mean urea was 38.17 ± 20.77 mmol/l (P = 0.0024) in the control group. Histological changes in the control group included inflammatory infiltration, tubular damage, and architectural distortion. These were not seen in the treatment group. Seven days post-operatively the survival rate of treated mice was 100% compared to 50% in the control group (P = 0.015).

Interpretation: In this single kidney mouse model, pretreatment with HIL-6 administration effectively protected against IR-I both morphologically and functionally. Further studies are needed to better understand the mechanism and feasibility of using this immunomodulator.

Preconditioning against renal ischaemia reperfusion injury: the failure to translate to the clinic

Acute kidney injury (AKI) as a result of ischaemia-reperfusion represents a major healthcare burden worldwide. Mortality rates from AKI in hospitalized patients are extremely high and have changed little despite decades of research and medical advances. In 1986, Murry et al. demonstrated for the first time the phenomenon of ischaemic preconditioning to protect against ischaemia-reperfusion injury (IRI). This seminal finding paved the way for a broad body of research, which attempted to understand and ultimately harness this phenomenon for human application. The ability of preconditioning to limit renal IRI has now been demonstrated in multiple different animal models. However, more than 30 years later, a safe and consistent method of protecting human organs, including the kidneys, against IRI is still not available. This review highlights agents which, despite strong preclinical data, have recently failed to reduce AKI in human trials. The multiple reasons which may have contributed to the failure to translate some of the promising findings to clinical therapies are discussed. Agents which hold promise in the clinic because of their recent efficacy in preclinical large animal models are also reviewed.

Protective effect of zinc preconditioning against renal ischemia reperfusion injury is dose dependent

Objectives

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury and chronic kidney disease. Two promising preconditioning methods for the kidney, intermittent arterial clamping (IC) and treatment with the hypoxia mimetic cobalt chloride, have never been directly compared. Furthermore, the protective efficacy of the chemically related transition metal Zn²⁺ against renal IRI is unclear. Although Co²⁺ ions have been shown to protect the kidney via hypoxia inducible factor (HIF), the effect of Zn²⁺ ions on the induction of HIF1α, HIF2α and HIF3α has not been investigated previously.

Materials and methods

The efficacy of different preconditioning techniques was assessed using a Sprague-Dawley rat model of renal IRI. Induction of HIF proteins following Zn²⁺ treatment of the human kidney cell lines HK-2 (immortalized normal tubular cells) and ACHN (renal cancer) was measured using Western Blot.

Results

Following 40 minutes of renal ischemia in rats, cobalt preconditioning offered greater protection against renal IRI than IC as evidenced by lower peak serum creatinine and urea concentrations. ZnCl₂ (10 mg/kg) significantly lowered the creatinine and urea concentrations compared to saline-treated control rats following a clinically relevant 60 minutes of ischemia. Zn²⁺ induced expression of HIF1α and HIF2α but not HIF3α in HK-2 and ACHN cells.

Conclusion

ZnCl₂ preconditioning protects against renal IRI in a dose-dependent manner. Further studies are warranted to determine the possible mechanisms involved, and to assess the benefit of ZnCl₂ preconditioning for clinical applications.

Amelioration of renal ischemia-reperfusion injury with a novel protective cocktail

PURPOSE

Extended warm ischemia during partial nephrectomy can lead to considerable renal injury. Using a rat model of renal ischemia we examined the ability of a unique renoprotective cocktail to ameliorate warm ischemia-reperfusion injury.

MATERIALS AND METHODS

A warm renal ischemia model was developed using 60 Sprague-Dawley® rats. The left renal artery was clamped for 40 minutes, followed by 48 hours of reperfusion. A renoprotective cocktail of a mixture of specific growth factors, mitochondria protecting biochemicals and Manganese-Porphyrin (MnTnHex-2-PyP(5+)) was given intramuscularly at -24, 0 and 24 hours after surgery. At 48 hours the 2 kidneys were harvested and examined with hematoxylin and eosin, and periodic acid-Schiff stains. Protein and gene expression were also analyzed to determine ischemia markers and the antioxidant response.

RESULTS

Compared to ischemic controls, kidneys treated with the renoprotective cocktail showed significant reversal of morphological changes and a significant decrease in the specific ischemic markers lipocalin-2, mucin-1 and galectin-3. Quantitative reverse transcriptase-polymerase chain reaction revealed up-regulation of several antioxidant genes in treated animals.

CONCLUSIONS

According to histopathological and several molecular measures our unique renoprotective cocktail mitigated ischemia-reperfusion injury.

Renoprotective effect of Linum usitatissimum seeds through haemodynamic changes and conservation of antioxidant enzymes in renal ischaemia-reperfusion injury in rats

Objective

To evaluate an ethanolic extract of seeds of Linum usitatissimum (Linn.) (EELU) for its renoprotective role in rats through its antihypertensive effect and conservation of biological oxidation enzymes.

Materials and methods

Male Wistar rats (200–250 g) underwent uninephrectomy on day 0; after 2 weeks of recovery, the nephrectomised rats were divided into four groups of eight each: (I) sham (II); renal ischaemia reperfusion (RIR); (III) RIR + EELU 200 mg/kg; and (IV) RIR + EELU 400 mg/kg. In group II, III and IV the renal artery was occluded for 45 min and reperfused for 4 weeks; the sham group did not undergo RIR.

Results

EELU (400 mg/kg) significantly decreased the haemodynamic changes after 4 weeks of RIR injury. EELU treatment significantly restored the levels of renal endogenous antioxidant enzymes and membrane-bound enzymes. EELU 400 mg/kg restored the levels of blood urea nitrogen and serum creatinine. EELU also decreased the levels of tumour necrosis factor-α and myeloperoxidase activity. A flow-cytometric study confirmed a significant decrease in cellular necrosis and increase in viability after RIR in EELU-treated rats. The anti-apoptotic role of EELU was evident from the decrease in DNA fragmentation. Renal tissue damage as assessed by histopathology was decreased in groups III and IV (200 and 400 mg/kg EELU).

Conclusion

We conclude that EELU protected the kidney against RIR-induced renal injury, probably by inhibiting reactive oxygen species that have a causal role in such cases. It also inhibits apoptotic cell death and inflammation, and improves haemodynamic changes.

Utilization of an in vivo reporter for high throughput identification of branched small molecule regulators of hypoxic adaptation

Small molecules inhibiting hypoxia inducible factor (HIF) prolyl hydroxylases (PHDs) are the focus of drug development efforts directed toward the treatment of ischemia and metabolic imbalance. A cell-based reporter produced by fusing HIF-1 alpha oxygen degradable domain (ODD) to luciferase was shown to work as a capture assay monitoring stability of the overexpressed luciferase-labeled HIF PHD substrate under conditions more physiological than in vitro test tubes. High throughput screening identified novel catechol and oxyquinoline pharmacophores with a "branching motif" immediately adjacent to a Fe-binding motif that fits selectively into the HIF PHD active site in in silico models. In accord with their structure-activity relationship in the primary screen, the best "hits" stabilize HIF1 alpha, upregulate known HIF target genes in a human neuronal line, and exert neuroprotective effects in established model of oxidative stress in cortical neurons.