Minocycline prevents osmotic demyelination associated with aquaresis

Prolonged extracellular low sodium concentrations and subsequent their rapid correction modulate nitric oxide production dependent on NFAT5 in microglia

Hyponatremia is the most common clinical electrolyte disorder. Chronic hyponatremia has been recently reported to be associated with falls, fracture, osteoporosis, neurocognitive impairment, and mental manifestations. In the treatment of chronic hyponatremia, overly rapid correction of hyponatremia can cause osmotic demyelination syndrome (ODS), a central demyelinating disease that is also associated with neurological morbidity and mortality. Using a rat model, we have previously shown that microglia play a critical role in the pathogenesis of ODS. However, the direct effect of rapid correction of hyponatremia on microglia is unknown. Furthermore, the effect of chronic hyponatremia on microglia remains elusive. Using microglial cell lines BV-2 and 6-3, we show here that low extracellular sodium concentrations (36 mmol/L decrease; LS) suppress Nos2 mRNA expression and nitric oxide (NO) production of microglia. On rapid correction of low sodium concentrations, NO production was significantly increased in both cells, suggesting that acute correction of hyponatremia partly directly contributes to increased Nos2 mRNA expression and NO release in ODS pathophysiology. LS also suppressed expression and nuclear translocation of nuclear factor of activated T cells-5 (NFAT5), a transcription factor that regulates the expression of genes involved in osmotic stress. Furthermore, overexpression of NFAT5 significantly increased Nos2 mRNA expression and NO production in BV-2 cells. Expressions of Nos2 and Nfat5 mRNA were also modulated in microglia isolated from cerebral cortex in chronic hyponatremia model mice. These data indicate that LS modulates microglial NO production dependent on NFAT5 and suggest that microglia contribute to hyponatremia-induced neuronal dysfunctions.

Effects of hypernatremia on the microglia

Signs and symptoms of hypernatremia largely indicate central nervous system dysfunction. Acute hypernatremia can cause demyelinating lesions similar to that observed in osmotic demyelination syndrome (ODS). We have previously demonstrated that microglia accumulate in ODS lesions and minocycline protects against ODS by inhibiting microglial activation. However, the direct effect of rapid rise in the sodium concentrations on microglia is largely unknown. In addition, the effect of chronic hypernatremia on microglia also remains elusive. Here, we investigated the effects of acute (6 or 24 h) and chronic (the extracellular sodium concentration was increased gradually for at least 7 days) high sodium concentrations on microglia using the microglial cell line, BV-2. We found that both acute and chronic high sodium concentrations increase NOS2 expression and nitric oxide (NO) production. We also demonstrated that the expression of nuclear factor of activated T-cells-5 (NFAT5) is increased by high sodium concentrations. Furthermore, NFAT5 knockdown suppressed NOS2 expression and NO production. We also demonstrated that high sodium concentrations decreased intracellular Ca2+ concentration and an inhibitor of Na+/Ca2+ exchanger, NCX, suppressed a decrease in intracellular Ca2+ concentrations and NOS2 expression and NO production induced by high sodium concentrations. Furthermore, minocycline inhibited NOS2 expression and NO production induced by high sodium concentrations. These in vitro data suggest that microglial activity in response to high sodium concentrations is regulated by NFAT5 and Ca2+ efflux through NCX and is suppressed by minocycline.

Kidney-tonifying blood-activating decoction delays ventricular remodeling in rats with chronic heart failure by regulating gut microbiota and metabolites and p38 mitogen-activated protein kinase/p65 nuclear factor kappa-B/aquaporin-4 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Myocardial infarction has likely contributed to the increased prevalence of heart failure(HF).As a result of ventricular remodeling and reduced cardiac function, colonic blood flow decreases, causing mucosal ischemia and hypoxia of the villous structure of the intestinal wall.This damage in gut barrier function increases bowel wall permeability, leading to fluid metabolism disorder,gut microbial dysbiosis, increased gut bacteria translocation into the circulatory system and increased circulating endotoxins, thus promoting a typical inflammatory state.Traditional Chinese Medicine plays a key role in the prevention and treatment of HF.Kidney-tonifying Blood-activating(KTBA) decoction has been proved for clinical treatment of chronic HF.However,the mechanism of KTBA decoction on chronic HF is still unclear.

AIMS OF THE STUDY

The effect of KTBA decoction on gut microbiota and metabolites and p38MAPK/p65NF-κB/AQP4 signaling in rat colon was studied to investigate the mechanism that KTBA decoction delays ventricular remodeling and regulates water metabolism disorder in rats with HF after myocardial infarction based on the theory of "Kidney Storing Essence and Conducting Water".

MATERIAL AND METHODS

In vivo,a rat model of HF after myocardial infarction was prepared by ligating the left anterior descending coronary artery combined with exhaustive swimming and starvation.The successful modeling rats were randomly divided into five groups:model group, tolvaptan group(gavaged 1.35mg/(kg•D) tolvaptan),KTBA decoction group(gavaged 15.75g/(kg•D) of KTBA decoction),KTBA decoction combined with SB203580(p38MAPK inhibitor) group(gavaged 15.75g/(kg•D) of KTBA decoction and intraperitoneally injected 1.5mg/(kg•D) of SB203580),and KTBA decoction combined with PDTC(p65NF-kB inhibitor) group(gavaged 15.75g/(kg•D) of KTBA decoction and intraperitoneally injected 120mg/(kg•D) of PDTC).The sham-operation group and model group were gavaged equal volume of normal saline.After 4 weeks of intervention with KTBA decoction,the effect of KTBA decoction on the cardiac structure and function of chronic HF model rats was observed by ultrasonic cardiogram.General state and cardiac index in rats were evaluated.Enzyme linked immunosorbent assay(ELISA) was used to measure N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration in rat serum.Hematoxylin and eosin(H&E) staining,and transmission electron microscope(TEM) were used to observe the morphology and ultrastructure of myocardial and colonic tissue,and myocardial fibrosis was measured by Masson's staining.Cardiac E-cadherin level was detected by Western blot.The mRNA expression and protein expression levels of p38MAPK,I-κBα, p65NF-κB,AQP4,Occludin and ZO-1 in colonic tissue were detected by reverse transcription-quantitative real-time polymerase chain reaction(RT-qPCR) and immunohistochemistry. Protein expression of p38MAPK, p-p38MAPK,I-κBα,p-I-κBα,p65NF-κB, p-p65NF-κB,AQP4,Occludin and ZO-1 in rat colon was detected using Western blot.Colonic microbiota and serum metabolites were respectively analyzed by amplicon sequencing and liquid chromatography-mass spectrometry.In vitro, CCD-841CoN cell was placed in the ischemic solution under hypoxic conditions (94%N2,5%CO2,and 1%O2) in a 37 °C incubator to establish an ischemia and hypoxia model.The CCD-841CoN cells were divided into 7 groups, namely blank group and model group with normal rat serum plus control siRNA, tolvaptan group with rat serum containing tolvaptan plus control siRNA, KTBA group with rat serum containing KTBA plus control siRNA, KTBA plus p38MAPK siRNA group, KTBA plus p65NF-κB siRNA group,and KTBA plus AQP4siRNA group.After 24h and 48h of intervention with KTBA decoction,RT-qPCR,immunofluorescence and Western blot was used to detect the mRNA expression and protein expression levels of p38MAPK,I-κBα,p65NF-κB,AQP4, Occludin and ZO-1 in CCD-841CoN cells.

RESULTS

Compared with the model, KTBA decoction improved the general state, decraesed the serum NT-proBNP level,HW/BW ratio, LVIDd and LVIDs, increased E-cadherin level,EF and FS,reduced number of collagen fibers deposited in the myocardial interstitium,and recovered irregular arrangement of myofibril and swollen or vacuolated mitochondria with broken crista in myocardium.Moreover, KTBA decoction inhibited the expression of p38MAPK,I-κBα,and p65NF-κB and upregulated AQP4, Occludin and ZO-1 in colon tissues and CCD-841CoN cells.Additionally,p38siRNA or SB203580, p65siRNA or PDTC, and AQP4siRNA partially weakened the protective effects of KTBA in vitro and vivo.Notably,The LEfSe analysis results showed that there were six gut biomaker bacteria in model group, including Allobaculum, Bacillales,Turicibacter, Turicibacterales,Turicibacteraceae,and Bacilli. Besides, three gut biomaker bacteria containing Deltaproteobacteria, Desulfovibrionaceae,and Desulfovibrionales were enriched by KTBA treatment in chronic HF model.There were five differential metabolites, including L-Leucine,Pelargonic acid, Capsidiol,beta-Carotene,and L- Erythrulose, which can be regulated back in the same changed metabolic routes by the intervention of KTBA.L-Leucine had the positive correlation with Bacillales, Turicibacterales,Turicibacteraceae,and Turicibacter.L-Leucine significantly impacts Protein digestion and absorption, Mineral absorption,and Central carbon metabolism in cancer regulated by KTBA, which is involved in the expression of MAPK and tight junction in intestinal epithelial cells.

CONCLUSIONS

KTBA decoction manipulates the expression of several key proteins in the p38MAPK/p65NF-κB/AQP4 signaling pathway, modulates gut microbiota and metabolites toward a more favorable profile, improves gut barrier function, delays cardiomyocyte hypertrophy and fibrosis,and improves cardiac function.

The Spectrum of Movement Disorders in Cases with Osmotic Demyelination Syndrome

Background

Osmotic demyelination syndrome (ODS) can be a central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM) based on the regions involved even though they share the same disease process, aetiopathogenesis and time course.

Objectives

Present study aims to characterize the clinical, radiological features and the outcome of patients with ODS with movement disorders as the forthcoming manifestation.

Methods

Chart review of patients with ODS with movement disorders. Demographic, clinical and radiological details of the patients were reviewed.

Results

Eleven patients (six females; mean age: 48.3 ± 17.6 years) were included in the study. Parkinsonism alone and parkinsonism with dystonia was noted in four patients each (36.4%) while dystonia alone was noted in the other 3 (27.3%). Five patients (45.5%) had postural tremors. While 5 patients had dystonia early in the course of illness (3-7 days), it was delayed (6-9 months) in the other 2. A triphasic course was noted in two patients. The first phase of hyponatremia induced neurological impairment was followed by a second phase of worsening due to the immediate effect of ODS and a third delayed phase of worsening due to delayed effect of ODS. MRI showed both EPM and CPM in eight patients, EPM alone in two patients and CPM alone in 1 patient. Nine patients had a good outcome with mRS < 3.

Conclusion

Parkinsonism and dystonia are important manifestations of ODS. Triphasic course with a delayed phase of worsening of movement disorders is probably due to the maladaptive neuronal repair. The concept of triphasic ODS is first being described in our series.

Osmotic Demyelination Syndrome Associated with Hypernatremia Caused by Lactulose Enema in a Patient with Chronic Alcoholism

A 44-year-old man with chronic alcoholism presented with seizure and loss of consciousness. He was diagnosed with alcoholic hepatic encephalopathy, and his neurologic symptoms recovered after lactulose enema treatment. His initial serum sodium level was 141mEq/L. However, his mental state became confused after treatment with lactulose enema for five days, and his serum sodium level increased to 178mEq/L. After five days of gradual correction of serum sodium level from 178mEq/L to 140mEq/L, the patient's mental state recovered, but motor weakness in both limbs remained. Therefore, magnetic resonance imaging of the brain was performed. T2-weighted brain images showed bilateral symmetrical hyperintensities in the central pons, basal ganglia, thalami, hippocampi and unci, which were consistent with central pontine and extrapontine myelinolysis. We report a rare case of osmotic demyelination syndrome that occurred as a result of a rapid increase from a normal sodium level to hypernatremia caused by lactulose enema administered to treat alcoholic hepatic encephalopathy.

Central Pontine Myelinosis and Osmotic Demyelination Syndrome

BACKGROUND

Osmotic demyelination syndrome (ODS), which embraces central pontine myelinolysis (CPM) and extrapontine myelinosis (EPM), is often underdiagnosed in clinical practice, but can be fatal. In this article, we review the etiology, patho- physiology, clinical features, diagnosis, treatment, and prognosis of ODS.

METHODS

Pertinent publications from the years 1959 to 2018 were retrieved by a selective search in PubMed.

RESULTS

The most common cause of ODS is hyponatremia; particular groups of patients, e.g., liver transplant recipients, are also at risk of developing ODS. The pathophysiology of ODS consists of cerebral apoptosis and loss of myelin due to osmotic stress. Accordingly, brain areas that are rich in oligodendrocytes and myelin tend to be the most frequently affected. Patients with ODS often have a biphasic course, the first phase reflecting the underlying predisposing illness and the second phase reflecting ODS itself, with pontine dysfunction, impaired vigilance, and movement disorders, among other neurological abnormalities. The diagnostic modality of choice is magnetic resonance imaging (MRI) of the brain, which can also be used to detect oligosymptomatic ODS. The current mainstay of management is prevention; treatment strategies for manifest ODS are still experimental. The prognosis has improved as a result of MRI-based diagnosis, but ODS can still be fatal (33% to 55% of patients either die or remain permanently dependent on nursing care).

CONCLUSION

ODS is a secondary neurological illness resulting from a foregoing primary disease. Though rare overall, it occurs with greater frequency in certain groups of patients. Clinicians of all specialties should therefore be familiar with the risk constellations, clinical presentation, and prevention of ODS. The treatment of ODS is still experimental at present, as no evidence-based treatment is yet available.

Osmotic Demyelination: From an Oligodendrocyte to an Astrocyte Perspective

Osmotic demyelination syndrome (ODS) is a disorder of the central myelin that is often associated with a precipitous rise of serum sodium. Remarkably, while the myelin and oligodendrocytes of specific brain areas degenerate during the disease, neighboring neurons and axons appear unspoiled, and neuroinflammation appears only once demyelination is well established. In addition to blood‒brain barrier breakdown and microglia activation, astrocyte death is among one of the earliest events during ODS pathology. This review will focus on various aspects of biochemical, molecular and cellular aspects of oligodendrocyte and astrocyte changes in ODS-susceptible brain regions, with an emphasis on the crosstalk between those two glial cells. Emerging evidence pointing to the initiating role of astrocytes in region-specific degeneration are discussed.

Astroglial Modulation of Hydromineral Balance and Cerebral Edema

Maintenance of hydromineral balance (HB) is an essential condition for life activity at cellular, tissue, organ and system levels. This activity has been considered as a function of the osmotic regulatory system that focuses on hypothalamic vasopressin (VP) neurons, which can reflexively release VP into the brain and blood to meet the demand of HB. Recently, astrocytes have emerged as an essential component of the osmotic regulatory system in addition to functioning as a regulator of the HB at cellular and tissue levels. Astrocytes express all the components of osmoreceptors, including aquaporins, molecules of the extracellular matrix, integrins and transient receptor potential channels, with an operational dynamic range allowing them to detect and respond to osmotic changes, perhaps more efficiently than neurons. The resultant responses, i.e., astroglial morphological and functional plasticity in the supraoptic and paraventricular nuclei, can be conveyed, physically and chemically, to adjacent VP neurons, thereby influencing HB at the system level. In addition, astrocytes, particularly those in the circumventricular organs, are involved not only in VP-mediated osmotic regulation, but also in regulation of other osmolality-modulating hormones, including natriuretic peptides and angiotensin. Thus, astrocytes play a role in local/brain and systemic HB. The adaptive astrocytic reactions to osmotic challenges are associated with signaling events related to the expression of glial fibrillary acidic protein and aquaporin 4 to promote cell survival and repair. However, prolonged osmotic stress can initiate inflammatory and apoptotic signaling processes, leading to glial dysfunction and a variety of brain diseases. Among many diseases of brain injury and hydromineral disorders, cytotoxic and osmotic cerebral edemas are the most common pathological manifestation. Hyponatremia is the most common cause of osmotic cerebral edema. Overly fast correction of hyponatremia could lead to central pontine myelinolysis. Ischemic stroke exemplifies cytotoxic cerebral edema. In this review, we summarize and analyze the osmosensory functions of astrocytes and their implications in cerebral edema.

Chronic Hyponatremia Causes Neurologic and Psychologic Impairments

Hyponatremia is the most common clinical electrolyte disorder. Once thought to be asymptomatic in response to adaptation by the brain, recent evidence suggests that chronic hyponatremia may be linked to attention deficits, gait disturbances, risk of falls, and cognitive impairments. Such neurologic defects are associated with a reduction in quality of life and may be a significant cause of mortality. However, because underlying diseases such as adrenal insufficiency, heart failure, liver cirrhosis, and cancer may also affect brain function, the contribution of hyponatremia alone to neurologic manifestations and the underlying mechanisms remain unclear. Using a syndrome of inappropriate secretion of antidiuretic hormone rat model, we show here that sustained reduction of serum sodium ion concentration induced gait disturbances; facilitated the extinction of a contextual fear memory; caused cognitive impairment in a novel object recognition test; and impaired long-term potentiation at hippocampal CA3-CA1 synapses. In vivo microdialysis revealed an elevated extracellular glutamate concentration in the hippocampus of chronically hyponatremic rats. A sustained low extracellular sodium ion concentration also decreased glutamate uptake by primary astrocyte cultures, suggesting an underlying mechanism of impaired long-term potentiation. Furthermore, gait and memory performances of corrected hyponatremic rats were equivalent to those of control rats. Thus, these results suggest chronic hyponatremia in humans may cause gait disturbance and cognitive impairment, but these abnormalities are reversible and careful correction of this condition may improve quality of life and reduce mortality.

Identification of the novel autoantigen candidate Rab GDP dissociation inhibitor alpha in isolated adrenocorticotropin deficiency

Isolated adrenocorticotropin deficiency (IAD) is characterized by low or absent adrenocorticotropic hormone (ACTH) production. IAD is presumed to be caused in part by an autoimmune mechanism, and several lines of evidence have suggested the presence of anti-pituitary antibodies in IAD. However, the exact autoantigens remain unknown. The present study was designed to identify the autoantigen(s) in IAD using chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Rat anterior pituitary lysate was subjected to SDS-PAGE, and immunoblotting was performed using the sera from two patients with IAD and from a healthy subject. The bands detected by the patient serum samples, but not by the healthy subject sample, were excised, in-gel digested using trypsin, and subjected to LC-MS/MS analysis. On immunoblots, a 51-kDa band in the insoluble pellet was detected by the sera from the IAD patients but not from the healthy subject. Mass spectrometric analysis revealed the 51-kDa band contained Rab guanine nucleotide dissociation inhibitor (GDI) alpha. Consistent with the mass spectrometric analysis, a recombinant full-length human Rab GDI alpha was recognized by the two IAD patient samples but not by the healthy subject sample using immunoblotting. In total, anti-Rab GDI alpha antibodies were detected in serum samples from three of five patients with IAD (60%) but were absent in 5 healthy subjects. In addition, Rab GDI alpha was expressed in the anterior pituitary. In conclusion, it appears that Rab GDI alpha is a candidate autoantigen involved in IAD, and that anti-Rab GDI alpha antibodies are present predominantly in patients with IAD.

Urea minimizes brain complications following rapid correction of chronic hyponatremia compared with vasopressin antagonist or hypertonic saline

Hyponatremia is a common electrolyte disorder that carries significant morbidity and mortality. However, severe chronic hyponatremia should not be corrected rapidly to avoid brain demyelination. Vasopressin receptor antagonists (vaptans) are now being widely used for the treatment of hyponatremia along with other alternatives like hypertonic saline. Previous reports have suggested that, in some cases, urea can also be used to correct hyponatremia. Correction of severe hyponatremia with urea has never been compared to treatment with a vaptan or hypertonic saline with regard to the risk of brain complications in the event of a too rapid rise in serum sodium. Here, we compared the neurological outcome of hyponatremic rats corrected rapidly with urea, lixivaptan, and hypertonic saline. Despite similar increase in serum sodium obtained by the three drugs, treatment with lixivaptan or hypertonic saline resulted in a higher mortality than treatment with urea. Histological analysis showed that treatment with urea resulted in less pathological change of experimental osmotic demyelination than was induced by hypertonic saline or lixivaptan. This included breakdown of the blood-brain barrier, microglial activation, astrocyte demise, and demyelination. Thus, overcorrection of hyponatremia with urea resulted in significantly lower mortality and neurological impairment than the overcorrection caused by lixivaptan or hypertonic saline.