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Lipin 1 is an intracellular protein acting as a phosphatidic acid phosphohydrolase enzyme controlling lipid metabolism. Human recessive mutations in LPIN1 cause recurrent, early-onset myoglobinuria, a condition normally associated with muscle pain and weakness. Whether and how lipin 1 deficiency in humans leads to peripheral neuropathy is yet unclear. Herein, two novel compound heterozygous mutations in LPIN1 with neurological disorders, but no myoglobinuria were identified in an adult-onset syndromic myasthenia family. The present study sought to explore the pathogenic mechanism of LPIN1 in muscular and neural development. Methods: The clinical diagnosis of the proband was compared to the known 48 cases of LPIN1 recessive homozygous mutations. Whole-exome sequencing was carried out on the syndromic myasthenia family to identify the causative gene. The pathogenesis of lipin 1 deficiency during somitogenesis and neurogenesis was investigated using the zebrafish model. Whole-mount in situ hybridization, immunohistochemistry, birefringence analysis, touch-evoke escape response and locomotion assays were performed to observe in vivo the changes in muscles and neurons. The conservatism of the molecular pathways regulated by lipin 1 was evaluated in human primary glioblastoma and mouse myoblast cells by siRNA knockdown, drug treatment, qRT-PCR and Western blotting analysis. Results: The patient exhibited adult-onset myasthenia accompanied by muscle fiber atrophy and nerve demyelination without myoglobinuria. Two novel heterozygous mutations, c.2047A>C (p.I683L) and c.2201G>A (p.R734Q) in LPIN1 , were identified in the family and predicted to alter the tertiary structure of LPIN1 protein. Lipin 1 deficiency in zebrafish embryos generated by lpin1 morpholino knockdown or human LPIN1 mutant mRNA injections reproduced the myotomes defects, a reduction both in primary motor neurons and secondary motor neurons projections, morphological changes of post-synaptic clusters of acetylcholine receptors, and myelination defects, which led to reduced touch-evoked response and abnormalities of swimming behaviors. Loss of lipin 1 function in zebrafish and mammalian cells also exhibited altered expression levels of muscle and neuron markers, as well as abnormally enhanced Notch signaling, which was partially rescued by the specific Notch pathway inhibitor DAPT. Conclusions: These findings pointed out that the compound heterozygous mutations in human LPIN1 caused adult-onset syndromic myasthenia with peripheral neuropathy. Moreover, zebrafish could be used to model the neuromuscular phenotypes due to the lipin 1 deficiency, where a novel pathological role of over-activated Notch signaling was discovered and further confirmed in mammalian cell lines., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Myoglobinuric acute renal failure (MARF) may develop after severe muscle injury. Heme oxygenase-1 (HO-1), a stress-response protein, has been implicated as a protective agent against MARF. We hypothesized that hyperbaric oxygen therapy (HBOT) may alleviate MARF by inducing renal HO-1 expression. Wistar-Albino rats were randomly assigned into three groups: Control (n = 4), MARF (n = 8), MARF + HBO (n = 8). MARF was induced by intramuscular glycerol (50%, 8 mL/kg) injection. Saline (8 mL/kg) was injected into the hind limb of the animals in the control group. Animals in the MARF + HBO group received two sessions of HBO therapy (90 min at 2.5 atm) 2 and 18 h after glycerol injection. Serum and tissue samples were taken at 24 h. Serum urea and creatinine levels increased in the MARF and MARF + HBO groups confirming the development of MARF. But, serum urea and creatinine levels were similar in MARF and MARF + HBO groups. Oxidative stress parameters were similar among all groups. Histological renal injury score was similar in MARF and MARF + HBO groups. HO-1 level, determined by immunohistochemistry, was significantly higher in MARF and MARF + HBO groups, compared to the control group. Although HO-1 level in MARF + HBO group was higher than MARF group, it was not statistically significant. We found that HBOT did not reduce renal injury in experimental MARF model. HBOT is used to reduce the muscle damage after crush injury, which may be accompanied by MARF. Therefore, more studies are needed to understand the effects of HBO treatment on renal functions after MARF.

Rhabdomyolysis accounts for ∼10% of acute kidney injuries. In glycerol-induced myoglobinuric acute kidney injury, we found an increase in the nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear protein, a key redox-sensitive transcription factor, and Nrf2-regulated genes and proteins including upregulation of heme oxygenase-1. In in vitro studies, pretreatment of LLC-PK1 cells with an activator of Nrf2 before myoglobin exposure significantly decreased oxidant generation and cytotoxicity, whereas Nrf2 inhibition and gene silencing exacerbated the injury. Chlormethiazole, a specific CYP2E1 transcription inhibitor, prevented an increase in catalytic iron in the kidneys, decreased oxidative stress, blocked nuclear translocation of the Nrf2 protein, decreased heme oxygenase-1 upregulation, and provided functional and histological protection against acute kidney injury. CYP2E1 inhibitors and gene silencing in renal tubular epithelial cells significantly decreased reactive oxygen species generation and provided marked protection against myoglobin-induced cytotoxicity. Thus, during CYP2E1-induced oxidative stress, the transcription factor Nrf2 has a pivotal role in the early adaptive response. Inhibition of CYP2E1 coupled with the prior induction of Nrf2 may be a valuable tool to reduce CYP2E1-mediated rhabdomyolysis-induced acute kidney injury.

Myoglobinuric acute renal failure (ARF) is a uremic syndrome caused by traumatic or non-traumatic skeletal muscle breakdown and intracellular elements that are released into the bloodstream. We hypothesized that hyperbaric oxygen (HBO) therapy could be beneficial in the treatment of myoglobinuric ARF caused by rhabdomyolysis. A total of 32 rats were used in the study. The rats were divided into four groups: control, control+hyperbaric oxygen (control+HBO), ARF, and ARF+hyperbaric oxygen (ARF+HBO). Glycerol (8 ml/kg) was injected into the hind legs of each of the rats in ARF and ARF+HBO groups. 2.5 atmospheric absolute HBO was applied to the rats in the control+HBO and ARF+HBO groups for 90 min on two consecutive days. Plasma urea, creatinine, sodium, potassium, calcium, aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase, creatinine kinase and urine creatinine and sodium were examined. Creatinine clearance and fractional sodium excretion could then be calculated. Superoxide dismutase, catalase, glutathione and malondialdehyde (MDA) levels were assessed in renal tissue. Tissue samples were evaluated by Hematoxylin-eosin, PCNA and TUNEL staining histopathologically. MDA levels were found to be significantly decreased whereas SOD and CAT were twofold higher in the ARF+HBO group compared to the ARF group. Renal function tests were ameliorated by HBO therapy. Semiquantitative evaluation of histopathological findings indicated that necrosis and cast formation was decreased by HBO therapy and TUNEL staining showed that apoptosis was inhibited. PCNA staining showed that HBO therapy did not increase regeneration. Ultimately, we conclude that, in accordance with our hypothesis, HBO could be beneficial in the treatment of myoglobinuric ARF.

A(3) adenosine receptor (AR) activation and inhibition worsen and improve, respectively, renal function after ischemia-reperfusion (I/R) injury in rats. We sought to further characterize the role of A(3) ARs in modulating renal function after either I/R or myoglobinuric renal injury. A(3) knockout mice had significantly lower plasma creatinines compared with C57 controls 24 h after I/R or myoglobinuric renal injury. C57 control mice pretreated with the A(3) AR antagonist [3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5 dicarboxylate] or agonist [0.125 mg/kg N(6)-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine (IB-MECA)] demonstrated improved or worsened renal function, respectively, after I/R or myoglobinuric renal injury. Higher doses of IB-MECA were lethal in C57 mice subjected to renal ischemia. H(1) but not H(2) histamine receptor antagonist prevented death in mice pretreated with IB-MECA before renal ischemia. Improvement in renal function was associated with significantly improved renal histology. In conclusion, preischemic A(3) AR activation (0.125 mg/kg IB-MECA) exacerbated renal I/R injury in mice. Mice lacking A(3) ARs or blocking A(3) ARs in wild-type mice resulted in significant renal protection from ischemic or myoglobinuric renal failure.

Background: Renal cortical/proximal tubule cholesterol accumulation, with preferential localization within plasma membrane "detergent resistant microdomains" (DRMs: rafts/caveolae), is a hallmark of the maintenance phase of acute renal failure (ARF). This study addressed two related issues: (1) Are maintenance-phase cholesterol increases accompanied by an up-regulation of caveolin, a DRM/caveolar-associated cholesterol binding protein? (2) Is DRM cholesterol/caveolin homeostasis acutely altered during the induction phase of ARF?, Methods: Mouse kidneys were subjected to ischemia +/- reperfusion (I/R) followed by assessment of cholesterol DRM partitioning. Acute cell injury effects on potential caveolin release from isolated proximal tubules or into urine also were assessed. Finally, renal cortical/isolated proximal tubule caveolin levels were determined 18 hours after I/R or myoglobinuric ARF., Results: Acute ischemia causes a rapid shift of cholesterol into cortical DRMs (>22%). Cholesterol migration into DRMs also was observed in ATP-depleted cultured proximal tubule (HK-2) cells. Acute hypoxic or toxic tubule injury induced plasma membrane caveolin release (Western blot). By the maintenance phase of ARF, marked renal cortical/proximal tubule caveolin increases resulted., Conclusions: Acute proximal tubular injury damages caveolar/DRM structures, as determined by cholesterol maldistribution and caveolin release. Post-injury, there is a dramatic up-regulation of renal cortical/proximal tubule caveolin, suggesting an increased caveolar mass. These findings indicate, to our knowledge for the first time, that dysregulation of caveolae/raft microdomain expression is a correlate of, and potential participant in, the induction and maintenance phases of ischemic and toxic forms of experimental ARF.

Iron catalyzed free radical formation and lipid peroxidation are accepted mechanisms of heme protein-induced acute renal failure. However, the source(s) of those free radicals which trigger lipid peroxidation in proximal tubular cells remains unknown. This study tested the potential involvement of mitochondrial electron transport, xanthine oxidase activity, and arachidonic acid metabolism in the heme-induced peroxidative state. The impact of cytosolic Ca2+ loading also was assessed. Rhabdomyolysis was induced in mice by glycerol injection, and two hours later heme-laden proximal tubular segments (PTS) were isolated for study. PTS from normal mice served as controls. During 30 to 60 minute incubations, heme loaded PTS developed progressive cytotoxicity (LDH release) and iron-dependent lipid peroxidation (malondialdehyde, MDA, generation; inhibited by deferoxamine). Site 2 (antimycin A) or site 3 (cyanide, hypoxia) mitochondrial respiratory chain inhibition completely blocked lipid peroxidation, whereas site 1 inhibition (rotenone) doubled its extent (presumably by shunting NADH through NADH dehydrogenase, a free radical generating system). Conversely, these agents did not substantially alter MDA in normal PTS. Normal and heme loaded PTS developed comparable degrees of LDH release during respiratory blockade irrespective of increased or decreased MDA production (indicating that lipid peroxidation was not a critical determinant of cell death). Neither increasing free arachidonic acid (PLA2 treatment) nor adding cyclooxygenase/lipoxygenase/cytochrome p450 inhibitors conferred a consistent protective effect. Altering free Ca2+ status (chelators; ionophore addition) and xanthine oxidase inhibition had no discernible impacts. Despite mitochondrial free radical production, mitochondrial function, as assessed by the ATP/ADP ratio, seemingly remained intact. In conclusion, (1) the terminal mitochondrial respiratory chain is the dominant source of free radicals which trigger PTS lipid peroxidation; (2) iron is a required secondary factor; (3) although mitochondria fuel lipid peroxidation, they do not appear to be critical targets of the heme-induced oxidant attack.

Mannitol (M) and deferoxamine (DFO) can each protect against myohemoglobinuric acute renal failure (MH-ARF). This study assessed M-DFO interactions during MH-ARF to help discern mechanisms of renal injury, and to define whether M + DFO exerts additive or synergistic antioxidant/cytoprotective effects. Rats subjected to the glycerol model of MH-ARF were treated with (a) M; (b) DFO; (c) M + DFO; or (d) no protective agents. Relative degrees of protection (24-h plasma urea/creatinine concentrations) were M + DFO greater than M greater than DFO greater than or equal to no therapy. To assess whether catalytic Fe is generated during MH-ARF, the bleomycin assay was applied to plasma/urine samples obtained 0-2 h post-glycerol injection. Although striking plasma and urinary increments were noted, excess renal hydroxyl radical (.OH) production was not apparent (gauged by the salicylate trap method). M increased catalytic Fe excretion (four times), whereas DFO eliminated its urinary (but not plasma) activity. To determine direct M/DFO effects on proximal tubular cell oxidant injury, isolated rat proximal tubular segments (PTS) were incubated with toxic dosages of FeSO4 or H2O2. Despite inducing cell injury (lactic dehydrogenase release), Fe caused no .OH production. DFO conferred dose-dependent cytoprotection, correlating with increased, not decreased, .OH generation. Although M scavenged this .OH excess, it had no additive or independent, protective effect. H2O2 cytotoxicity correlated with increased catalytic Fe (but not .OH) generation. The fact that DFO (but not .OH scavengers [M and dimethylthiourea]) blocked H2O2 toxicity implied Fe-dependent, .OH-independent cell killing. In conclusion, (a) striking catalytic Fe generation occurs during MH-ARF, but augmented intrarenal .OH production may not develop; (b) DFO can block Fe toxicity despite a prooxidant effect; (c) H2O2 PTS toxicity is Fe, but possibly not .OH, dependent; and (d) M does not mitigate oxidant PTS injury, either in the presence or absence of DFO, suggesting that its additive benefit with DFO in vivo occurs via a diuretic, not antioxidant effect.

A 36-year-old man was admitted because of sopor and dark urine after intravenous amphetamine injection. He subsequently developed myoglobinuria and acute renal failure. Serum myoglobin value was remarkably elevated to 83,000 ng/ml, and urine myoglobin was 400,000 ng/ml. Renal biopsy revealed tubular degeneration and tubular obstruction with myoglobin casts by immunofluorescence examination. Amphetamine-induced rhabdomyolysis was suspected to cause myoglobinuric acute renal failure.

Studies were undertaken to determine whether significant abnormalities were present in cardiac myoglobin in a case of primary paroxysmal myoglobinuria.No qualitative abnormality was found in cardiac myoglobin from a patient with myoglobinuria, compared to normal controls, using urea starch gel electrophoresis. Quantitative analysis, however, revealed depletion of cardiac myoglobin in the patient with myoglobinuria.It is considered that the basic defect in primary paroxysmal myoglobinuria is not related to myoglobin per se, and although evidence is lacking, an autoimmune process, as encountered in some of the hemolytic anemias, may be involved in this condition.