Role of peroxynitrite and recombinant human manganese superoxide dismutase in reducing ischemia-reperfusion renal tissue injury

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

SIRT2 tyrosine nitration by peroxynitrite in response to renal ischemia/reperfusion injury

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the production of renal ischemia/reperfusion (I/R). The current study is to elucidate a mechanism of SIRT2 tyrosine nitration to accelerate the cell apoptosis induced by peroxynitrite (ONOO‾), the most reactive and deleterious RNS type in renal ischemia/reperfusion (I/R) injury. Our results demonstrate that there is a significant enhancement of the 3-nitrotyrosine levels in renal tissues of Acute Kidney Injury (AKI) patients and rats that underwent renal I/R, and a positive correlation between the 3-nitrotyrosine level and renal function impairment, indicative of an accumulation of peroxynitrite. Notably, peroxynitrite-evoked nitration of SIRT2 destroyed its enzymatic activity and the capability to deacetylate FOXO3a, and enhanced expression of Bim and caspase3, facilitating renal cell apoptosis in renal ischemia/reperfusion and SIN-1(peroxynitrite donor) treatment in vitro, and these effects were reversed by FeTMPyP, a peroxynitrite decomposition scavenger. Importantly, we identified that the tyrosine 86 is responsible for SIRT2 nitration and inactivation using site-mutation assay and Mass Spectrography analysis. Altogether, these findings point to a novel protective mechanism that an inhibition of SIRT2 tyrosine nitration can be a promising strategy to prevent ischemic renal diseases involving AKI.

The Effects of Meldonium on the Renal Acute Ischemia/Reperfusion Injury in Rats

Acute renal ischemia/reperfusion (I/R) injury is a clinical condition that is challenging to treat. Meldonium is an anti-ischemic agent that shifts energy production from fatty acid oxidation to less oxygen-consuming glycolysis. Thus, in this study we investigated the effects of a four-week meldonium pre-treatment (300 mg/kg b.m./day) on acute renal I/R in male rats (Wistar strain). Our results showed that meldonium decreased animal body mass gain, food and water intake, and carnitine, glucose, and lactic acid kidney content. In kidneys of animals subjected to I/R, meldonium increased phosphorylation of mitogen-activated protein kinase p38 and protein kinase B, and increased the expression of nuclear factor erythroid 2-related factor 2 and haeme oxygenase 1, causing manganese superoxide dismutase expression and activity to increase, as well as lipid peroxidation, cooper-zinc superoxide dismutase, glutathione peroxidase, and glutathione reductase activities to decrease. By decreasing the kidney Bax/Bcl2 expression ratio and kidney and serum high mobility group box 1 protein content, meldonium reduced apoptotic and necrotic events in I/R, as confirmed by kidney histology. Meldonium increased adrenal noradrenaline content and serum, adrenal, hepatic, and renal ascorbic/dehydroascorbic acid ratio, which caused complex changes in renal lipidomics. Taken together, our results have confirmed that meldonium pre-treatment protects against I/R-induced oxidative stress and apoptosis/necrosis.

Inadequate Antioxidative Responses in Kidneys of Brain-Dead Rats

BACKGROUND

Brain death (BD)-related lipid peroxidation, measured as serum malondialdehyde (MDA) levels, correlates with delayed graft function in renal transplant recipients. How BD affects lipid peroxidation is not known. The extent of BD-induced organ damage is influenced by the speed at which intracranial pressure increases. To determine possible underlying causes of lipid peroxidation, we investigated the renal redox balance by assessing oxidative and antioxidative processes in kidneys of brain-dead rats after fast and slow BD induction.

METHODS

Brain death was induced in 64 ventilated male Fisher rats by inflating a 4.0F Fogarty catheter in the epidural space. Fast and slow inductions were achieved by an inflation speed of 0.45 and 0.015 mL/min, respectively, until BD confirmation. Healthy non-brain-dead rats served as reference values. Brain-dead rats were monitored for 0.5, 1, 2, or 4 hours, after which organs and blood were collected.

RESULTS

Increased MDA levels became evident at 2 hours of slow BD induction at which increased superoxide levels, decreased glutathione peroxidase (GPx) activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased plasma creatinine levels were evident. At 4 hours after slow BD induction, superoxide, MDA, and plasma creatinine levels increased further, whereas GPx activity remained decreased. Increased MDA and plasma creatinine levels also became evident after 4 hours fast BD induction.

CONCLUSION

Brain death leads to increased superoxide production, decreased GPx activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased MDA and plasma creatinine levels. These effects were more pronounced after slow BD induction. Modulation of these processes could lead to decreased incidence of delayed graft function.

Prion Protein Protects against Renal Ischemia/Reperfusion Injury

The cellular prion protein (PrP^C), a protein most noted for its link to prion diseases, has been found to play a protective role in ischemic brain injury. To investigate the role of PrP^C in the kidney, an organ highly prone to ischemia/reperfusion (IR) injury, we examined wild-type (WT) and PrP^C knockout (KO) mice that were subjected to 30-min of renal ischemia followed by 1, 2, or 3 days of reperfusion. Renal dysfunction and structural damage was more severe in KO than in WT mice. While PrP was undetectable in KO kidneys, Western blotting revealed an increase in PrP in IR-injured WT kidneys compared to sham-treated kidneys. Compared to WT, KO kidneys exhibited increases in oxidative stress markers heme oxygenase-1, nitrotyrosine, and N^ε-(carboxymethyl)lysine, and decreases in mitochondrial complexes I and III. Notably, phosphorylated extracellular signal-regulated kinase (pERK) staining was predominantly observed in tubular cells from KO mice following 2 days of reperfusion, a time at which significant differences in renal dysfunction, histological changes, oxidative stress, and mitochondrial complexes between WT and KO mice were observed. Our study provides the first evidence that PrP^C may play a protective role in renal IR injury, likely through its effects on mitochondria and ERK signaling pathways.

Effect of a recombinant manganese superoxide dismutase on prevention of contrast-induced acute kidney injury

BACKGROUND

Contrast media (CM)-induced nephropathy (CIN) is an acute deterioration of renal function following administration of CM mediated to a large extent by the increased production of ROS within the kidney. Aim of this study was to evaluate whether a novel isoform of a recombinant Manganese SOD (rMnSOD) could provide an effective protection against CIN; this molecule shares the same ability of physiological SODs in scavenging reactive oxygen species (ROS) but, due to its peculiar properties, enters inside the cells after its administration.

METHODS

We studied the effects rMnSOD on oxidative damage in a rat model of CIN in uninephrectomized rats, that were randomly assigned to 3 experimental Groups: Group CON, control rats treated with the vehicle of CM, Group HCM, rats treated with CM and Group SOD, rats treated with CM and rMnSOD.

RESULTS

In normal rats, pretreatment with rMnSOD, reduced renal superoxide anion production, induced by the activation of NAPDH oxidase, by 84 % (p < 0.001). In rats of Group HCM, ROS production was almost doubled compared to rat of Group CON (p < 0.01) but returned to normal values in rats of Group SOD, where a significant increase of SOD activity was detected (+16 % vs HCM, p < 0.05). Administration of CM determined a striking fall of GFR in rats of Group HCM (-70 %, p < 0.001 vs CON), greatly blunted in Group SOD (-28 % vs CON, p < 0.01); this was associated with a lower presence of both tubular necrosis and intratubular casts in SOD-treated rats (both p < 0.01 vs Group HCM).

CONCLUSIONS

Our data indicate that rMnSOD is able to reduce renal oxidative stress, thus preventing the reduction of GFR and the renal histologic damage that follows CM administration.

Altered mitochondrial functioning induced by preoperative fasting may underlie protection against renal ischemia/reperfusion injury

We reported previously that the robust protection against renal ischemia/reperfusion (I/R) injury in mice by fasting was largely initiated before the induction of renal I/R. In addition, we found that preoperative fasting downregulated the gene expression levels of complexes I, IV, and V of the mitochondrial oxidative phosphorylation (OXPHOS) system, while it did not change those of complexes II and III. Hence, we now investigated the effect of 3 days of fasting on the functioning of renal mitochondria in order to better understand our previous findings. Fasting did not affect mitochondrial density. Surprisingly, fasting significantly increased the protein expression of complex II of the mitochondrial OXPHOS system by 19%. Complex II-driven state 3 respiratory activity was significantly reduced by fasting (46%), which could be partially attributed to the significant decrease in the enzyme activity of complex II (16%). Fasting significantly inhibited Ca(2+) -dependent mitochondrial permeability transition pore opening that is directly linked to protection against renal I/R injury. The inhibition of the mitochondrial permeability transition pore did not involve the expression of the voltage-dependent anion channel by fasting. In conclusion, 3 days of fasting clearly induces the inhibition of complex II-driven mitochondrial respiration state 3 in part by decreasing the amount of functional complex II, and inhibits mitochondrial permeability transition pore opening. This might be a relevant sequence of events that could contribute to the protection of the kidney against I/R injury.

Recombinant human manganese superoxide dismutase reduces liver fibrosis and portal pressure in CCl4-cirrhotic rats

BACKGROUND & AIMS

High oxidative stress plays a major role in increasing hepatic vascular resistance in cirrhosis, by facilitating liver fibrosis and by increasing hepatic vascular tone. This study is aimed at investigating whether the use of the novel isoform of recombinant human manganese superoxide dismutase (rMnSOD) could be a new therapeutic strategy to reduce oxidative stress and portal hypertension in cirrhotic rats.

METHODS

In CCl(4)- and BDL-cirrhotic rats treated with rMnSOD (i.p. 15 μg/kg/day) or its vehicle for 7 days, mean arterial pressure (MAP), portal pressure (PP) and portal blood flow (PBF) or small mesenteric arterial flow (SMABF) were measured. In addition, in CCl(4)-cirrhotic rats, we evaluated the hepatic vasodilatory response to acetylcholine, liver fibrosis with Sirius red staining and hepatic stellate cell activation by α-smooth muscle actin (α-SMA) protein expression.

RESULTS

rMnSOD treatment significantly reduced PP either in CCl(4)- or BDL-cirrhotic rats without significant changes in splanchnic blood flow, suggesting a reduction in hepatic vascular resistance. MAP was not modified. Reduction in PP was associated with a significant reduction in liver fibrosis, and α-SMA protein expression as well as with improved vasodilatory response to acetylcholine.

CONCLUSIONS

Chronic rMnSOD administration to cirrhotic rats reduces portal pressure by reducing hepatic vascular resistance without deleterious effects on systemic hemodynamics, suggesting that it might constitute a new antioxidant to be considered as additional therapy for treating portal hypertension in cirrhosis.

Role of reduced manganese superoxide dismutase in ischemia-reperfusion injury: a possible trigger for autophagy and mitochondrial biogenesis?

Excessive generation of superoxide and mitochondrial dysfunction has been described as being important events during ischemia-reperfusion (I/R) injury. Our laboratory has demonstrated that manganese superoxide dismutase (MnSOD), a major mitochondrial antioxidant that eliminates superoxide, is inactivated during renal transplantation and renal I/R and precedes development of renal failure. We hypothesized that MnSOD knockdown in the kidney augments renal damage during renal I/R. Using newly characterized kidney-specific MnSOD knockout (KO) mice the extent of renal damage and oxidant production after I/R was evaluated. These KO mice (without I/R) exhibited low expression and activity of MnSOD in the distal nephrons, had altered renal morphology, increased oxidant production, but surprisingly showed no alteration in renal function. After I/R the MnSOD KO mice showed similar levels of injury to the distal nephrons when compared with wild-type mice. Moreover, renal function, MnSOD activity, and tubular cell death were not significantly altered between the two genotypes after I/R. Interestingly, MnSOD KO alone increased autophagosome formation, mitochondrial biogenesis, and DNA replication/repair within the distal nephrons. These findings suggest that the chronic oxidative stress as a result of MnSOD knockdown induced multiple coordinated cell survival signals including autophagy and mitochondrial biogenesis, which protected the kidney against the acute oxidative stress following I/R.

LMP-420, a small molecular inhibitor of TNF-α, prolongs islet allograft survival by induction of suppressor of cytokine signaling-1: synergistic effect with cyclosporin-A

Inflammatory insults following islet transplantation (ITx) hinders engraftment and long-term function of the transplanted (Tx) islets. Using a murine model of ITx, we determined the role of LMP-420, a novel TNF-α inhibitor, both individually and in combination with the immunosuppressant cyclosporine A (CSA) in islet engraftment and survival. Diabetic C57BL/6 mice were Tx with 500 BALB/c islets under the kidney capsule. Four cohorts were used: LMP-420 only, CSA only, combination of LMP-420 and CSA (LMP+CSA), and control (n = 12 per cohort). Serial monitoring of blood glucose levels revealed that LMP+CSA (35 ± 5 days) prolonged stable blood insulin levels compared to control (6 ± 4 days). Immunohistology demonstrated that coadministration (LMP+CSA) results in a significant decrease in CD8(+) T-cell infiltration (LMP+CSA: 31 ± 18 vs. control: 224 ± 51 cells, p < 0.001). Serum cytokine analysis revealed that LMP-420 administration resulted in an increase in the anti-inflammatory cytokine IL-10 (2.5-fold), and a decrease in TNF-α (threefold) with no change in IL-2. However, coadministration resulted in a marked decrease in both IL-2 and TNF-α (threefold) along with increase in IL-10 (threefold). Coadministration also demonstrated increase of antiapoptotic SOCS-1 and Mn-SOD expression and significant reduction of donor-specific antibodies (p < 0.005). In conclusion, LMP-420 administration with CSA results in the upregulation of anti-inflammatory and antiapoptotic mechanisms which facilitate islet allograft engraftment and survival.

High-level soluble expression of recombinant human manganese superoxide dismutase in Escherichia coli, and its effects on proliferation of the leukemia cell

Manganese superoxide dismutase (Mn-SOD) is one of the major enzymes responsible for the defense against oxidative damage due to reactive oxygen species (ROS) in the mitochondria. The present study aimed to produce and evaluate the genetically engineered manganese superoxide dismutase protein. A recombinant plasmid containing DNA segment coding Mn-SOD protein was transformed into Escherichia coli (E. coli) Rosetta-gami strain, for expression. After induction with IPTG, an expected molecular mass of 25 kDa was detected by SDS-PAGE. After Ni-NTA affinity chromatography purification, the purity rate came up to 95%. UV spectroscopy data for our preparations indicated that a peak at 275 nm existed in the spectrum. SOD activity assay showed that the activity of the rhMn-SOD was 1890.9 U/mg. The ORAC level of rhMn-SOD was 151492.2 uM Trolox equiv/mg. Furthermore, in vitro bioactivity assay indicated that the rhMn-SOD protein can inhibit the proliferation of the leukemia K562 cells.

Peroxynitrite mediates active site tyrosine nitration in manganese superoxide dismutase. Evidence of a role for the carbonate radical anion

Protein tyrosine nitration has been observed in a variety of human diseases associated with oxidative stress, such as inflammatory, neurodegenerative, and cardiovascular conditions. However, the pathways leading to nitration of tyrosine residues are still unclear. Recent studies have shown that peroxynitrite (PN), produced by the reaction of superoxide and nitric oxide, can lead to protein nitration and inactivation. Tyrosine nitration may also be mediated by nitrogen dioxide produced by the oxidation of nitrite by peroxidases. Manganese superoxide dismutase (MnSOD), which plays a critical role in cellular defense against oxidative stress by decomposing superoxide within mitochondria, is nitrated and inactivated under pathological conditions. In this study, MnSOD is shown to catalyze PN-mediated self-nitration. Direct, spectroscopic observation of the kinetics of PN decay and nitrotyrosine formation (k(cat) = 9.3 × 10(2) M(-1) s(-1)) indicates that the mechanism involves redox cycling between Mn(2+) and Mn(3+), similar to that observed with superoxide. Distinctive patterns of tyrosine nitration within MnSOD by various reagents were revealed and quantified by MS/MS analysis of MnSOD trypsin digest peptides. These analyses showed that three of the seven tyrosine residues of MnSOD (Tyr34, Tyr9, and Tyr11) were the most susceptible to nitration and that the relative amounts of nitration of these residues varied widely depending upon the nature of the nitrating agent. Notably, nitration mediated by PN, in both the presence and absence of CO2, resulted in nitration of the active site tyrosine, Tyr34, while nitration by freely diffusing nitrogen dioxide led to surface nitration at Tyr9 and Tyr11. Flux analysis of the nitration of Tyr34 by PN-CO2 showed that the nitration rate coincided with the kinetics of the reaction of PN with CO2. These kinetics and the 20-fold increase in the efficiency of tyrosine nitration in the presence of CO2 suggest a specific role for the carbonate radical anion (•CO3(-)) in MnSOD nitration by PN. We also observed that the nitration of Tyr34 caused inactivation of the enzyme, while nitration of Tyr9 and Tyr11 did not interfere with the superoxide dismutase activity. The loss of MnSOD activity upon Tyr34 nitration implies that the responsible reagent in vivo is peroxynitrite, acting either directly or through the action of •CO3(-).