The cellular hydration state: a critical determinant for cell death and survival

Analysis of hemodynamics and impedance using bioelectrical impedance analysis in hypovolemic shock-induced swine model

To treat hypovolemic shock, fluid infusion or blood transfusion is essential to address insufficient volume. Much controversy surrounds resuscitation in hypovolemic shock. We aimed to identify the ideal fluid combination for treating hypovolemic shock-induced swine model, analyzing bioelectrical impedance and hemodynamics. Fifteen female three-way crossbred pigs were divided into three different groups. The three resuscitation fluids were (1) balanced crystalloid, (2) balanced crystalloid + 5% dextrose water, and (3) balanced crystalloid + 20% albumin. The experiment was divided into three phases and conducted sequentially: (1) controlled hemorrhage (1 L bleeding, 60 min), (2) resuscitation phase 1 (1 L fluid infusion, 60 min), and (3) resuscitation phase 2 (1 L fluid infusion, 60 min). Bioelectrical impedance analysis was implemented with a segmental multifrequency bioelectrical impedance analyzer. A total of 61 impedance measurements were assessed for each pig at six different frequencies in five segments of the pig. Pulse rate (PR), mean arterial pressure (MAP), stroke volume (SV), and stroke volume variation (SVV) were measured using a minimally invasive hemodynamic monitoring device. The three-dimensional graph showed a curved pattern when infused with 1 L of balanced crystalloid + 1 L of 5% dextrose water and 1.6 L of balanced crystalloid + 400 ml of 20% albumin. The 1M impedance increased in all groups during the controlled hemorrhage, and continuously decreased from fluid infusion to the end of the experiment. Only balanced crystalloid + 20% albumin significantly restored MAP and SV to the same level as the start of the experiment after the end of fluid infusion. There were no significant differences in MAP and SV from the time of recovery to the initial value of 1M impedance to the end of fluid infusion in all groups. The change and the recovery of hemodynamic indices such as MAP and SV coincide with the change and the recovery of 1M impedance. Using balanced crystalloid mixed with 20% albumin in hypovolemic shock-induced swine model may be helpful in securing hemodynamic stability, compared with balanced crystalloid single administration.

Chirality-Selected Coacervate by Chiral Gemini Surfactant

Chiral surfactants present opportunities to self-assemble into supramolecules with a chiral trait; however, the effects of stereochemistry on the formation of simple coacervates remain unclear. Here, we investigate the chirality-selected phase behavior in mixtures of chiral gemini surfactant 1,4-bis(dodecyl-N,N-dimethylammonium bromide)-2,3-butanediol (12-4(OH)2-12) with an oppositely charged chiral mandelic acid (MA). It demonstrates that altering the chirality of surfactants yields a heightened ability to regulate the phase behavior, leading to the formation of three different network-like structures, i.e., wormlike micelle, coacervate, and hydrogel, in the racemate, enantiomer, and mesomer, respectively. The different aggregate structures arise from the intermolecular and intramolecular hydrogen-bond interactions of the two hydroxyl groups located at stereogenic centers. Intriguingly, although they contain similar microstructures, the solid-like hydrogel and liquid-like wormlike micelle show similar low hydration ability and have no encapsulation capability, whereas only coacervate formed by the enantiomers of 12-4(OH)2-12 displays liquid-like characteristics, strong capacity to sequester diverse solutes, and high affinity for tightly bound water simultaneously. These findings further highlight the unique and advantageous properties of coacervates as a promising model for exploring the biological process and understanding how chirality plays a crucial role in early life scenarios and cell evolution at the molecular level.

Influence of Impaired Hydration Status on Postoperative in-Hospital Death in Patients with Acute Type A Aortic Dissection

Background

The hydration state of the body is getting more and more attention from researchers. The purpose of this study is to investigate the relationship between impaired hydration status and postoperative hospitalization death in patients with A AAD.

Methods

From January 2019 to October 2021, the clinical data of 299 patients undergoing A AAD surgery were retrospectively analyzed. Patients were divided into normal hydration group, imminent dehydration group and current dehydration group according to the dehydration standard at admission. Univariate and multivariate logistic regression analysis were used to determine the independent risk factors for in-hospital death of patients with A AAD.

Results

Postoperative in-hospital death in A AAD patients was significantly more common in the imminent and current dehydration groups (>295mmol/L) (26.7% vs 11.9%; P=0.001). The length of ICU stay was significantly longer in the impending and current dehydration groups (P<0.05). After controlling for other factors by multivariate logistic regression analysis, the results showed that the group of impending and current dehydration (>295) (OR=3.61, 95% confidence interval [CI]: 1.61-8.06; P=0.002), CRRT (OR=10.55, 95%[CI]: 3.59-31.01; P<0.001), lactic acid (OR=1.25, 95%[CI]: 1.13-1.38; P<0.001), CAD (OR=5.27, 95%[CI]: 1.12-24.80; P=0.035) was an independent risk factor for in-hospital death in A AAD patients. Albumin (OR=0.92, 95%[CI]: 0.85-0.99; P=0.040) is a protective factor.

Conclusion

The presence of high serum osmotic pressure on admission of A AAD patients can independently predict postoperative death, and the impaired body hydration status should be paid attention to.

Effects of Different Hydration Strategies in Young Men during Prolonged Exercise at Elevated Ambient Temperatures on Pro-Oxidative and Antioxidant Status Markers, Muscle Damage, and Inflammatory Status

Physical exercise is associated with an increase in the speed of metabolic processes to supply energy to working muscles and endogenous heat production. Intense sweating caused by the work performed at high ambient temperatures is associated with a significant loss of water and electrolytes, leading to dehydration. This study aimed to examine the effectiveness of different hydration strategies in young men during prolonged exercise at elevated ambient temperatures on levels of pro-oxidative and antioxidant status, oxidative status markers (TAC/TOC), muscle cell damage (Mb, LDH), and inflammatory status (WBC, CRP, IL-1β). The study was conducted on a group of 12 healthy men with average levels of aerobic capacity. The intervention consisted of using various hydration strategies: no hydration; water; and isotonic drinks. The examination was di-vided into two main stages. The first stage was a preliminary study that included medical exami-nations, measurements of somatic indices, and exercise tests. The exercise test was performed on a cycle ergometers. Their results were used to determine individual relative loads for the main part of the experiment. In the second stage, the main study was conducted, involving three series of weekly experimental tests using a cross-over design. The change in plasma volume (∆PV) measured im-mediately and one hour after the exercise test was significantly dependent on the hydration strategy (p = 0.003 and p = 0.002, respectively). The mean values of oxidative status did not differ signifi-cantly between the hydration strategy used and the sequence in which the test was performed. Using isotonic drinks, due to the more efficient restoration of the body’s water and electrolyte balance compared to water or no hydration, most effectively protects muscle cells from the negative effects of exercise, leading to heat stress of exogenous and endogenous origin.

Oxidative and osmotolerant effects in Salvator merianae (Squamata: Teiidae) red blood cells during hibernation

Hibernation is a natural condition of animals that lives in the temperate zone, although some tropical lizards also experience hibernation annually, such as the lizard native from South America, Salvator merianae, or "tegu" lizard. Even though physiological and metabolic characteristic associated with hibernation have been extensively studied, possible alterations in the red blood cells (RBC) integrity during this period remains unclear. Dehydration and fasting are natural consequences of hibernating for several months and it could be related to some cellular modifications. In this study, we investigated if the osmotic tolerance of RBCs of tegu lizard under hibernation is different from the cells obtained from animals while normal activity. Additionally, we indirectly investigated if the RBCs membrane of hibernating tegus could be associated with oxidation by quantifying oxidized biomolecules and the activity of antioxidant enzymes. Our findings suggest that RBCs are more fragile during the hibernation period, although we did not find evidence of an oxidative stress scenario associated with the accentuated fragility. Even though we did not exclude the possibility of oxidative damage during hibernation, we suggested that an increased RBCs volume as a consequence of hypoosmotic blood during hibernation could also affect RBCs integrity as noted.

Dose-Effect/Toxicity of Bupleuri Radix on Chronic Unpredictable Mild Stress and Normal Rats Based on Liver Metabolomics

Depression, one of the most prevalent psychiatric diseases, affects the quality of life of millions of people. Studies have shown that the lower polar fraction of Bupleuri Radix (PBR) elicited therapeutic effects in chronic unpredictable mild stress (CUMS) rats. In contrast, comparatively mild liver injury was observed in normal rats administered a high PBR dose. It is essential to clarify the effective and safe dose of PBR and its dose-effect/toxicity relationship. In this study, we used the CUMS model to evaluate the effects and toxicities of PBR and to decipher the dose-effect/toxicity relationship and mechanism using the liver metabonomics combined with multivariate statistical analysis. In CUMS rats, PBR improved the depression-like behaviors including reduced body growth rate, anhedonia, and locomotor activities, and markedly reduced the contents of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In control rats, PBR treatment altered ALT and AST from typical levels. Moreover, the effective dose range for CUMS rats was 12.6–163 g (herb)/kg, the median toxicity dose for CUMS and normal rats were 388 and 207 g (herb)/kg. The toxicological results showed that the cytokeratin-18 fragment level was increased significantly in CUMS rats given with 100 g (herb)/kg PBR. After a comprehensive analysis, the use of PBR dose was determined to be 12.6–50 g (herb)/kg. In CUMS rats, PBR could reverse amino acid metabolism, energy metabolism, sphingolipid metabolism, and β-oxidation of fatty acids to produce an anti-depressant effect in a dose-dependent manner. In control rats, two additional metabolic pathways were significantly perturbed by PBR, including glycerophospholipid metabolism and bile acid metabolism. Moreover, the comprehensive metabolic index including dose-effect index (DEI) and dose toxicity index (DTI) had a remarkable ability (ROC = 0.912, ROC = 0.878) to predict effect and toxicity. The DEI and DTI were used to determine the dose range of effect and toxicity which was shown high concordance with previous results. Furthermore, the CUMS rats possessed a higher toxicity tolerance dose of PBR which was consistent with the theory of “You Gu Wu Yun” in traditional Chinese medicine. The metabonomics techniques combined with correlation analysis could be used to discover indicators for comprehensive evaluations of efficacy and toxicity.

Impaired hydration status in acutely admitted older patients: prevalence and impact on mortality

BACKGROUND

impaired hydration is common in the older people, however studies of its effects on outcome in the acute setting are limited.

OBJECTIVES

to assess (i) the prevalence of impaired hydration, (ii) its relationship with laboratory markers of altered hydration and with (iii) short- and long-term mortality.

DESIGN

retrospective cohort study.

SETTING

University Hospital-Internal Medicine Department.

SUBJECTS

a total of 5,113 older patients consecutively acutely admitted from October 2015 to July 2016.

METHODS

according to calculated serum osmolarity at admission hydration status was stratified in: low osmolarity (<275 mmol/L), euhydration (275-295 mmol/L), impending (296-300 mmol/L) and current dehydration (>300 mmol/L). Relationships with serum sodium, potassium, glucose, urea, estimated glomerular filtration rate (eGFR), haematocrit, urea/creatinine ratio (Urea/Cr) and urine specific gravity (USG) were determined. Charlson Comorbidity Index, Modified Early Warning Score, Glasgow Prognostic Score, Norton score and Nutritional Risk Screening-2002 were calculated.

RESULTS

current and impending dehydration, euhydration and low-osmolarity were detected in 51.7, 17.1, 28.5 and 2.7% of the patients, respectively. Osmolarity correlated with urea (r = 0.846). Associations with serum sodium, creatinine, eGFR and urea/Cr were low but significant, being negligible that with USG and haematocrit. Serum sodium and urea increased in the transition from low- to high-osmolarity (P < 0.001 in all pairwise comparisons). In multivariate modelling current dehydration, functional dependence, clinical instability and high nutritional risk were associated (P < 0.001) with reduced short- and long-term survival.

CONCLUSIONS

impaired hydration is common in older people acutely admitted to medical care and is associated with poor outcome. Early assessment of calculated serum osmolarity is mandatory to target dehydration and hypoosmolar disorders.

Oxidative stress in response to heat stress in wild caught Namaqua rock mice, Micaelamys namaquensis

Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the future, which are likely to result in the mass die-off of several species of organisms. Oxidative stress induced by severe heat stress has previously been associated with a reduction in animal cognitive performance, depressed reproduction and lower life expectancy. Little is known about the non-lethal consequences of species should they survive extreme heat exposure. We investigated the oxidative stress experienced by the Namaqua rock mouse, a nocturnal rodent, using two experimental heat stress protocols, a 6 hour acute heat stress protocol without access to water and a 3-day heatwave simulation with ad libitum water. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers of oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defence. Incubator heat stress (heat and dehydration stress) was brought about by increasing the body temperatures of animals to 39-40.8 °C for 6 hours. Following incubator heat stress, significantly higher levels of MDA were observed in the liver. Dehydration did not explain the variation in oxidative markers and is likely a combined effect of thermal and dehydration stress. Individual body mass was significantly negatively correlated to kidney SOD and lipid peroxidation. A heatwave was simulated using a temperature cycle that would naturally occur during a heatwave in the species' local habitat, with a maximal ambient temperature of 38 °C. Following the simulated heatwave, SOD activity of the kidney demonstrated significantly lowered activity suggesting oxidative stress. Current heat waves in this species have the potential of causing oxidative stress. Heat and dehydration stress following exacerbated temperatures are likely to incur significant oxidative stress in multiple tissues demonstrating the importance of water availability to allow for rehydration to prevent oxidative stress.

Heat and dehydration induced oxidative damage and antioxidant defenses following incubator heat stress and a simulated heat wave in wild caught four-striped field mice Rhabdomys dilectus

Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage, but little is known about the non-lethal consequences of surviving severe heat exposure. Severe heat exposure can cause oxidative stress which can have negative consequences on animal cognition, reproduction and life expectancy. We investigated the current oxidative stress experienced by a mesic mouse species, the four striped field mouse, Rhabdomys dilectus through a heat wave simulation with ad lib water and a more severe temperature exposure with minimal water. Wild four striped field mice were caught between 2017 and 2019. We predicted that wild four striped field mice in the heat wave simulation would show less susceptibility to oxidative stress as compared to a more severe heat stress which is likely to occur in the future. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers for oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defense. Incubator heat stress was brought about by increasing the body temperatures of animals to 39-40.8°C for 6 hours. A heat wave (one hot day, followed by a 3-day heatwave) was simulated by using temperature cycle that wild four striped field mice would experience in their local habitat (determined through weather station data using temperature and humidity), with maximal ambient temperature of 39°C. The liver and kidney demonstrated no changes in the simulated heat wave, but the liver had significantly higher SOD activity and the kidney had significantly higher lipid peroxidation in the incubator experiment. Dehydration significantly contributed to the increase of these markers, as is evident from the decrease in body mass after the experiment. The brain only showed significantly higher lipid peroxidation following the simulated heat wave with no significant changes following the incubator experiment. The significant increase in lipid peroxidation was not correlated to body mass after the experiment. The magnitude and duration of heat stress, in conjunction with dehydration, played a critical role in the oxidative stress experienced by each tissue, with the results demonstrating the importance of measuring multiple tissues to determine the physiological state of an animal. Current heat waves in this species have the potential of causing oxidative stress in the brain with future heat waves to possibly stress the kidney and liver depending on the hydration state of animals.

Anticataractogenic effect of betaine in chick embryo hydrocortisone-induced cataract model

Background & objectives:

Cataract is one of the leading causes of blindness in the world. The aim of the present study was to investigate anticataractogenic effect of betaine in chick embryo hydrocortisone (HC)-induced cataract model.

Methods:

The study included 60 fertilized eggs divided into six groups each having 10 eggs: one group treated with only HC (HC group); three treated with both HC and different doses of betaine (HC/B 1.00, HC/B 0.50 and HC/B 0.25 groups) and two non-HC groups treated with only phosphate-buffered saline (PBS group) or betaine (B group). After the injections, lenses of the embryos were removed and classified into five stages according to the lens opacification. The amounts of reduced glutathione (GSH) in the removed lenses were measured.

Results:

All the lenses in non-HC-treated groups were clear, whereas in the HC-treated group, 90 per cent of the lenses had cataract (stages 4 and 5). The mean score of lens opacity was significantly lower in all HC/B groups compared to HC group (2.4-3.5 vs. 4.4, P<0.05). Among HC/B groups, the HC/B 0.25 group had significantly lower mean score of lens opacity compared to remaining HC/B groups treated with higher doses of betaine. In addition, the mean reduced GSH level was significantly higher in HC/B 0.25 group compared to HC, HC/B 1.00 and HC/B 0.50 groups (P<0.001).

Interpretation & conclusions:

The present results show beneficial anti-cataract and anti-oxidant effects of 0.25 μmol/egg betaine on HC-induced cataract in the chick embryo.

Attenuation of heat stress-induced spermatogenesis complications by betaine in mice

High temperatures can induce oxidative stress, impairment of spermatogenesis, and reduction of sperm quality and quantity concomitant with transient periods of partial or complete infertility in male mammals. Promising beneficial effects of betaine supplementation on the epididymal spermatozoa have been reported in experimental studies; however, its effects on testicular heat stress (HS)-induced impairment have yet to be determined. In the present study, betaine (Bet) was orally administrated (250 mg/kg day) during a 14-day period, before (Bet + HS group) or after (HS + Bet group) induction of testicular HS in 7-9 week-old male mice. HS was induced by testicular immersion in water at 42 °C in stress groups. Epididymal spermatozoa and testes were collected at days 14 and 28 after HS induction in order to analyze sperm characteristics, testicular oxidative status, and histological changes. Our studies showed that HS reduced testicular weight, the quality and quantity of epididymal spermatozoa, and impaired maturation of germinal cells. The levels of MDA, catalase, SOD, and GPX were increased in the testes of HS-induced mice (P < 0.01). Although betaine treatment before and after exposure to HS enhanced antioxidant defense (P < 0.05) and accelerated germinal epithelium regeneration, its effects on the characteristics of epididymal spermatozoa were scarce. On the other hand, in the absence of heat stress, quality and quantity of epididymal spermatozoa were improved following 14 days of betaine consumption. Our study revealed the beneficial effect of betaine on HS-induced complications of spermatogenesis, as well as its potency to improve epididymal spermatozoa in intact mice.

Effect of exercise-induced dehydration on circulatory markers of oxidative damage and antioxidant capacity

Dehydration is a common event associated with exercise. However, few studies have examined the effects of dehydration on plasma redox status in humans. Eighty-two athletes were recruited and baseline anthropometrics and blood samples were obtained. Athletes then engaged in a dehydration protocol, training until 3% of preweight body mass was lost. Athletes returned to the lab and had postdehydration blood collected. Athletes then consumed an isotonic drink until pre-exercise body weight was reestablished. Blood was then recollected (1 h post full rehydration (PFR)). Samples were centrifuged and the plasma snap frozen in liquid nitrogen and stored at −80 °C. Lipid and protein oxidative stress was determined by measuring F2-isoprostanes and protein carbonyls (PC), respectively. Antioxidant capacity was determined by the ferric reducing ability of plasma (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays. Plasma osmolality was determined using an osmometer. Statistical analysis utilized a 1-way ANOVA with posthoc testing. Values are reported as mean ± SD. Plasma osmolality was significantly elevated immediately postdehydration (p ≤ 0.001) but decreased to baseline at PFR. Plasma TEAC increased immediately postdehydration and at PFR (p ≤ 0.001). FRAP increased immediately postdehydration (p ≤ 0.001) and decreased to below baseline at PFR (p ≤ 0.05). Conversely, F2-isoprostanes declined significantly from baseline to immediately postdehydration and then significantly rose at PFR (p ≤ 0.001), whereas PC declined at PFR (p ≤ 0.01). This study indicates that dehydration and exercise cause a significant increase in plasma osmolality and antioxidant potential immediately postexercise. We propose dehydration significantly elevates antioxidant concentration which suppresses F2-isoprostanes and PC.

Anti-caspase-3 preconditioning increases proinsulin secretion and deteriorates posttransplant function of isolated human islets

Human islet isolation is associated with adverse conditions inducing apoptosis and necrosis. The aim of the present study was to assess whether antiapoptotic preconditioning can improve in vitro and posttransplant function of isolated human islets. A dose-finding study demonstrated that 200 μmol/L of the caspase-3 inhibitor Ac-DEVD-CMK was most efficient to reduce the expression of activated caspase-3 in isolated human islets exposed to severe heat shock. Ac-DEVD-CMK-pretreated or sham-treated islets were transplanted into immunocompetent or immunodeficient diabetic mice and subjected to static glucose incubation to measure insulin and proinsulin secretion. Antiapoptotic pretreatment significantly deteriorated graft function resulting in elevated nonfasting serum glucose when compared to sham-treated islets transplanted into diabetic nude mice (p < 0.01) and into immunocompetent mice (p < 0.05). Ac-DEVD-CMK pretreatment did not significantly change basal and glucose-stimulated insulin release compared to sham-treated human islets but increased the proinsulin release at high glucose concentrations (20 mM) thus reducing the insulin-to-proinsulin ratio in preconditioned islets (p < 0.05). This study demonstrates that the caspase-3 inhibitor Ac-DEVD-CMK interferes with proinsulin conversion in preconditioned islets reducing their potency to cure diabetic mice. The mechanism behind this phenomenon is unclear so far but may be related to the ketone CMK linked to the Ac-DEVD molecule. Further studies are required to identify biocompatible caspase inhibitors suitable for islet preconditioning.

Metabolic perturbations of kidney and spleen in murine cerebral malaria: (1)H NMR-based metabolomic study

A significant fraction of global population is under the threat of malaria. Majority of annual death is due to the more complicated form of the infection i.e. the cerebral form, also known as Cerebral Malaria (CM). Host parasite interaction is known to cause a cascade of events in various tissues like brain, liver, kidney, and spleen. We have employed (1)H NMR based metabolomics to understand the specific perturbations of various tissues in CM. In our previous paper we have delineated the differences between CM vis-a-vis non-cerebral malaria (NCM) mice in serum, liver and brain. In this paper we focus on their differences of metabolic profile in kidney and spleen as kidney dysfunction and splenomegaly are known to be associated to neurological outcome of the disease. Moreover we have also looked into how the biological compartments (kidney, spleen and serum) interact with each other. The various metabolites involved in such interactions and their correlational aspects across the compartments have been studied in CM, NCM and control mice. The idea was to find out the specific pathways that are altered in CM mice. Our results demonstrate that both the kidney as well as spleen metabolism are differentially perturbed in CM with respect to NCM. The results point out that glutamate levels are decreased in CM mice with respect to NCM mice both in case of spleen and kidney while creatine, myo-inositol and betaine levels are increased in kidney of CM mice with respect to NCM mice. From the analysis of Multiway Principal Component Analysis (MPCA) we see that lipid metabolism and TCA cycle is altered in kidney and spleen.

PPIP5K1 modulates ligand competition between diphosphoinositol polyphosphates and PtdIns(3,4,5)P3 for polyphosphoinositide-binding domains

We describe new signalling consequences for PPIP5K1 (diphosphoinositol pentakisphosphate kinase type 1)-mediated phosphorylation of InsP6 and 5-InsP7 to 1-InsP7 and InsP8. In NIH 3T3 cells, either hyperosmotic stress or receptor activation by PDGF (platelet-derived growth factor) promoted translocation of PPIP5K1 from the cytoplasm to the plasma membrane. The PBD1 (polyphosphoinositide-binding domain) in PPIP5K1 recapitulated that translocation. Mutagenesis of PBD1 to reduce affinity for PtdIns(3,4,5)P3 prevented translocation. Using surface plasmon resonance, we found that PBD1 association with vesicular PtdIns(3,4,5)P3 was inhibited by InsP6 and diphosphoinositol polyphosphates. However, the inhibition by PPIP5K1 substrates (IC50: 5-InsP7=5 μM and InsP6=7 μM) was substantially more potent than that of the PPIP5K1 products (IC50: InsP8=32 μM and 1-InsP7=43 μM). This rank order of ligand competition with PtdIns(3,4,5)P3 was also exhibited by the PH (pleckstrin homology) domains of Akt (also known as protein kinase B), GRP1 (general receptor for phosphoinositides 1) and SIN1 (stress-activated protein kinase-interaction protein 1). We propose that, in vivo, PH domain binding of InsP6 and 5-InsP7 suppresses inappropriate signalling ('noise') from stochastic increases in PtdIns(3,4,5)P3. That restraint may be relieved by localized depletion of InsP6 and 5-InsP7 at the plasma membrane following PPIP5K1 recruitment. We tested this hypothesis in insulin-stimulated L6 myoblasts, using mTOR (mechanistic/mammalian target of rapamycin)-mediated phosphorylation of Akt on Ser473 as a readout for SIN1-mediated translocation of mTORC (mTOR complex) 2 to the plasma membrane [Zoncu, Efeyan and Sabatini (2011) Nat. Rev. Mol. Cell Biol. 12, 21-35]. Knockdown of PPIP5K1 expression was associated with a 40% reduction in Ser473 phosphorylation. A common feature of PtdIns(3,4,5)P3-based signalling cascades may be their regulation by PPIP5K1.

Osmotic regulation of hepatic betaine metabolism

Betaine critically contributes to the control of hepatocellular hydration and provides protection of the liver from different kinds of stress. To investigate how the hepatocellular hydration state affects gene expression of enzymes involved in the metabolism of betaine and related organic osmolytes, we used quantitative RT-PCR gene expression studies in rat hepatoma cells as well as metabolic and gene expression profiling in primary hepatocytes of both wild-type and 5,10-methylenetetrahydrofolate reductase (MTHFR)-deficient mice. Anisotonic incubation caused coordinated adaptive changes in the expression of various genes involved in betaine metabolism, in particular of betaine homocysteine methyltransferase, dimethylglycine dehydrogenase, and sarcosine dehydrogenase. The expression of betaine-degrading enzymes was downregulated by cell shrinking and strongly induced by an increase in cell volume under hypotonic conditions. Metabolite concentrations in the culture system changed accordingly. Expression changes were mediated through tyrosine kinases, cyclic nucleotide-dependent protein kinases, and JNK-dependent signaling. Assessment of hepatic gene expression using a customized microarray chip showed that hepatic betaine depletion in MTHFR(-/-) mice was associated with alterations that were comparable to those induced by cell swelling in hepatocytes. In conclusion, the adaptation of hepatocytes to changes in cell volume involves the coordinated regulation of betaine synthesis and degradation and concomitant changes in intracellular osmolyte concentrations. The existence of such a well-orchestrated response underlines the importance of cell volume homeostasis for liver function and of methylamine osmolytes such as betaine as hepatic osmolytes.

Oxidative Stress and DNA Damage Induced by Chromium in Liver and Kidney of Goldfish, Carassius auratus

Chromium (Cr) is an abundant element in the Earth’s crust. It exhibits various oxidation states, from divalent to hexavalent forms. Cr has diverse applications in various industrial processes and inadequate treatment of the industrial effluents leads to the contamination of the surrounding water resources. Hexavalent chromium (Cr (VI)) is the most toxic form, and its toxicity has been associated with oxidative stress. The present study was designed to investigate the toxic potential of Cr (VI) in fish. In this research, we investigated the role of oxidative stress in chromium-induced genotoxicity in the liver and kidney cells of goldfish, Carassius auratus. Goldfish were acclimatized to the laboratory conditions and exposed them to 5% and 10% of 96 hr-LC₅₀ (85.7 mg/L) of aqueous Cr (VI) in a continuous flow through system. Fish were sampled every 7 days for a period of 28 days to analyze the lipid hydroperoxides (LHP) levels and genotoxic potentials in the liver and kidney. LHP levels were analyzed by spectrophotometry while genotoxicity was assessed by single cell gel electrophoresis (comet) assay. LHP levels in the liver increased significantly at week 1, followed by a decrease. LHP levels in the kidney increased significantly at weeks 1, 2, and 3, and decreased at week 4 compared to the control. The percentage of DNA damage increased in both liver and kidney at both test concentrations. The results clearly indicate that Cr (VI) induces significant levels of DNA damage in liver and kidney cells of goldfish. The induced LHP levels in both organs were concentration-dependent and were directly correlated with the levels of DNA damage. The two tested Cr (VI) concentrations induced significant levels of oxidative stress in both organs, however the kidney appears to be more vulnerable and sensitive to Cr-induced toxicity than the liver.

Changes in lymph proteome induced by hemorrhagic shock: the appearance of damage-associated molecular patterns

BACKGROUND

Damage-associated molecular patterns (DAMPs) released from host tissue after trauma and hemorrhagic shock (HS) have been shown to activate polymorphonuclear cells (PMNs) and lead to acute lung injury and systemic inflammatory response syndrome. The avenue by which DAMPs reach the circulation is unclear; however post-HS lymph has been shown to contain biologically active mediators. We therefore studied the time course of DAMP detection in systemic lymph and the effect of isotonic versus hypertonic resuscitation on DAMPs production and PMN activation in vitro.

METHODS

A canine HS/hind-limb lymph cannulation model was used. Animals were bled to a mean arterial pressure of 40 mm Hg and were resuscitated with shed blood plus equivalent amounts of Na+as either lactated Ringer's solution or 7.5% hypertonic saline solution (HSS). Lymph samples were collected at baseline, end-shock, and at various times after resuscitation. DAMPs were isolated from lymph samples and detected by Western blot for high-mobility group box 1 and mitochondrial DNA. Priming of naive PMNs was indexed by mitogen-associated protein kinase phosphorylation. Human pulmonary microvascular endothelial cell monolayers were established and exposed to the various lymph samples. Endothelial intracellular adhesion molecule expression, apoptosis, and monolayer permeability were determined.

RESULTS

DAMPs were detected in lymph samples starting at the end of the shock period and peaking at 120 minutes after resuscitation. HSS resuscitation resulted in the highest levels of DAMPs detected in systemic lymph and plasma. PMN mitogen-associated protein kinase activation was noted during the resuscitation phase and peaked 120 minutes after resuscitation. Similar temporal changes in human pulmonary microvascular endothelial cell intracellular adhesion molecule expression and cellular injury were noted after shock with the greatest effect noted with the hypertonic saline resuscitation regimen.

CONCLUSION

Lymph represents an important avenue for the delivery of DAMPs into the systemic circulation after HS. HSS lead to a significant increase in DAMPs production in the model. This finding may account for the conflicting data regarding the salutary effects of HSS resuscitation noted in clinical versus experimental shock studies. ).

Variability of plasma and urine betaine in diabetes mellitus and its relationship to methionine load test responses: an observational study

Background

Since betaine is an osmolyte and methyl donor, and abnormal betaine loss is common in diabetes mellitus (>20% patients), we investigated the relationship between betaine and the post-methionine load rise in homocysteine, in diabetes and control subjects. The post-methionine load test is reported to be both an independent vascular risk factor and a measure of betaine sufficiency.

Methods

Patients with type 2 diabetes (n = 34) and control subjects (n = 17) were recruited. We measured baseline fasting plasma and 4-hour post-methionine load (L-methionine, 0.1 mg/kg body weight) concentrations of homocysteine, betaine, and the betaine metabolite N,N-dimethylglycine. Baseline urine excretions of betaine, dimethylglycine and glucose were measured on morning urine samples as the ratio to urine creatinine. Statistical determinants of the post-methionine load increase in homocysteine were identified in multiple linear regression models.

Results

Plasma betaine concentrations and urinary betaine excretions were significantly (p < 0.001) more variable in the subjects with diabetes compared with the controls. Dimethylglycine excretion (p = 0.00014) and plasma dimethylglycine concentrations (p = 0.039) were also more variable. In diabetes, plasma betaine was a significant negative determinant (p < 0.001) of the post-methionine load increase in homocysteine. However, it was not conclusive that this was different from the relationship in the controls. In the patients with diabetes, a strong relationship was found between urinary betaine excretion and urinary glucose excretion (but not with plasma glucose).

Conclusions

Both high and low plasma betaine concentrations, and high and low urinary betaine excretions, are more prevalent in diabetes. The availability of betaine affects the response in the methionine load test. The benefits of increasing betaine intake should be investigated.

Corticoadrenal activity in rat regulates betaine-homocysteine S-methyltransferase expression with opposite effects in liver and kidney

Betaine-homocysteine S-methyltransferase (BHMT) is an enzyme that converts homocysteine (Hcy) to methionine using betaine as a methyl donor. Betaine also acts as osmolyte in kidney medulla, protecting cells from high extracellular osmolarity. Hepatic BHMT expression is regulated by salt intake. Hormones, particularly corticosteroids, also regulate BHMT expression in rat liver. We investigated to know whether the corticoadrenal activity plays a role in kidney BHMT expression. BHMT activity in rat kidneys is several orders of magnitude lower than in rat livers and only restricted to the renal cortex. This study confirms that corticosteroids stimulate BHMT activity in the liver and, for the first time in an animal model, also up-regulate the BHMT gene expression. Besides, unlike the liver, corticosteroids in rat kidney down-regulate BHMT expression and activity. Given that the classical effect of adrenocortical activity on the kidney is associated with sodium and water re-absorption by the distal tubule leading to volume expansion, by promoting lesser use of betaine as a methyl donor, corticosteroids would preserve betaine for its other role as osmoprotectant against changes in the extracellular osmotic conditions. We conclude that corticosteroids are, at least in part, responsible for the inhibition of BHMT expression and activity in rat kidneys.

Exercise-induced dehydration with and without environmental heat stress results in increased oxidative stress

While in vitro work has revealed that dehydration and hyperthermia can elicit increased cellular and oxidative stress, in vivo research linking dehydration, hyperthermia, and oxidative stress is limited. The purpose of this study was to investigate the effects of exercise-induced dehydration with and without hyperthermia on oxidative stress. Seven healthy male, trained cyclists (power output (W) at lactate threshold (LT): 199 ± 19 W) completed 90 min of cycling exercise at 95% LT followed by a 5-km time trial (TT) in 4 trials: (i) euhydration in a warm environment (EU-W, control), (ii) dehydration in a warm environment (DE-W), (iii) euhydration in a thermoneutral environment (EU-T), and (iv) dehydration in a thermoneutral environment (DE-T) (W: 33.9 ± 0.9 °C; T: 23.0 ± 1.0 °C). Oxidized glutathione (GSSG) increased significantly postexercise in dehydration trials only (DE-W: p < 0.01, DE-T: p = 0.03), and while not significant, total glutathione (TGSH) and thiobarbituric acid reactive substances (TBARS) tended to increase postexercise in dehydration trials (p = 0.08 for both). Monocyte heat shock protein 72 (HSP72) concentration was increased (p = 0.01) while lymphocyte HSP32 concentration was decreased for all trials (p = 0.02). Exercise-induced dehydration led to an increase in GSSG concentration while maintenance of euhydration attenuated these increases regardless of environmental condition. Additionally, we found evidence of increased cellular stress (measured via HSP) during all trials independent of hydration status and environment. Finally, both 90-min and 5-km TT performances were reduced during only the DE-W trial, likely a result of combined cellular stress, hyperthermia, and dehydration. These findings highlight the importance of fluid consumption during exercise to attenuate thermal and oxidative stress during prolonged exercise in the heat.

Inhibiting ice recrystallization and optimization of cell viability after cryopreservation

The ice recrystallization inhibition activity of various mono- and disaccharides has been correlated with their ability to cryopreserve human cell lines at various concentrations. Cell viabilities after cryopreservation were compared with control experiments where cells were cryopreserved with dimethylsulfoxide (DMSO). The most potent inhibitors of ice recrystallization were 220 mM solutions of disaccharides; however, the best cell viability was obtained when a 200 mM d-galactose solution was utilized. This solution was minimally cytotoxic at physiological temperature and effectively preserved cells during freeze-thaw. In fact, this carbohydrate was just as effective as a 5% DMSO solution. Further studies indicated that the cryoprotective benefit of d-galactose was a result of its internalization and its ability to mitigate osmotic stress, prevent intracellular ice formation and/or inhibit ice recrystallization. This study supports the hypothesis that the ability of a cryoprotectant to inhibit ice recrystallization is an important property to enhance cell viability post-freeze-thaw. This cryoprotective benefit is observed in three different human cell lines. Furthermore, we demonstrated that the ability of a potential cryoprotectant to inhibit ice recrystallation may be used as a predictor of its ability to preserve cells at subzero temperatures.

Inhibition of interferon-α-induced signaling by hyperosmolarity and hydrophobic bile acids

Apart from viral conditions, host factors such as elevated bile acid concentrations are determinants of successful interferon-α (IFN-α) treatment in patients with chronic hepatitis C or B. The present study demonstrates that hydrophobic bile acids inhibit Jak1- and Tyk2-phosphorylation, which lead to blockade of STAT1-mediated IFN-α-signaling in the sodium-taurocholate cotransporting peptide (NTCP)-transfected human hepatoma cell line HepG2, resulting in a decreased mRNA and protein expression of IFN-stimulated genes such as myxovirus resistance protein A (MxA) or dsRNA-activated protein kinase (PKR). In addition, hyperosmotic stress leads to an inhibition of IFN-α-induced Jak1- and Tyk2-phosphorylation, and STAT1/STAT2-phosphorylation and gene expression. This inhibitory effect of hydrophobic bile acids or hyperosmolarity is not due to caspase-mediated cleavage or lysosomal degradation of the cognate receptors or to the generation of oxidative stress, activation of p38- or Erk-mediated MAPK pathways or phosphatase activity. Preincubation with the organic osmolyte betaine blocked the inhibitory effect of bile acids or hyperosmolarity on MxA protein expression, but had no effect on transcript levels or activation of STAT1, suggesting that betaine mediates its effects on MxA expression at a translational or post-translational level. Our findings could provide a rationale for betaine use in cholestatic HBV/HCV patients undergoing interferon therapy.

Choline and betaine in health and disease

Choline is an essential nutrient, but is also formed by de novo synthesis. Choline and its derivatives serve as components of structural lipoproteins, blood and membrane lipids, and as a precursor of the neurotransmitter acetylcholine. Pre-and postnatal choline availability is important for neurodevelopment in rodents. Choline is oxidized to betaine that serves as an osmoregulator and is a substrate in the betaine-homocysteine methyltransferase reaction, which links choline and betaine to the folate-dependent one-carbon metabolism. Choline and betaine are important sources of one-carbon units, in particular, during folate deficiency. Choline or betaine supplementation in humans reduces concentration of total homocysteine (tHcy), and plasma betaine is a strong predictor of plasma tHcy in individuals with low plasma concentration of folate and other B vitamins (B₂, B₆, and B₁₂) in combination TT genotype of the methylenetetrahydrofolate reductase 677 C->T polymorphism. The link to one-carbon metabolism and the recent availability of food composition data have motivated studies on choline and betaine as risk factors of chronic diseases previously studied in relation to folate and homocysteine status. High intake and plasma level of choline in the mother seems to afford reduced risk of neural tube defects. Intake of choline and betaine shows no consistent relation to cancer or cardiovascular risk or risk factors, whereas an unfavorable cardiovascular risk factor profile was associated with high choline and low betaine concentrations in plasma. Thus, choline and betaine showed opposite relations with key components of metabolic syndrome, suggesting a disruption of mitochondrial choline oxidation to betaine as part of the mitochondrial dysfunction in metabolic syndrome.

Diphosphoinositol polyphosphates: what are the mechanisms?

In countries where adulthood is considered to be attained at age eighteen, 2011 can be the point at which the diphosphoinositol polyphosphates might formally be described as "coming of age", since these molecules were first fully defined in 1993 (Menniti et al., 1993; Stephens et al., 1993b). But from a biological perspective, these polyphosphates cannot quite be considered to have matured into the status of being independently-acting intracellular signals. This review has discussed several of the published proposals for mechanisms by which the diphosphoinositol polyphosphates might act. We have argued that all of these hypotheses need further development.We also still do not know a single molecular mechanism by which a change in the levels of a particular diphosphoinositol polyphosphate can be controlled. Yet, despite all these gaps in our understanding, there is an enduring anticipation that these molecules have great potential in the signaling field. Reflecting our expectations of all teenagers, it should be our earnest hope that in the near future the diphosphoinositol polyphosphates will finally grow up.

Short-term effects of thyroid hormones during development: Focus on signal transduction

Extranuclear or nongenomic effects of thyroid hormones are mediated by receptors located at the plasma membrane or inside cells, and are independent of protein synthesis. Recently the alphaVbeta3 integrin was identified as a cell membrane receptor for thyroid hormones, and a wide variety of nongenomic effects have now been shown to be induced through binding of thyroid hormones to this receptor. However, also other thyroid hormone receptors can produce nongenomic effects, including the cytoplasmic TRalpha and TRbeta receptors and probably also a G protein-coupled membrane receptor, and increasing importance is now given to thyroid hormone metabolites like 3,5-diiodothyronine and reverse T(3) that can mimick some nongenomic effects of T(3) and T(4). Signal transduction from the alphaVbeta3 integrin may proceed through at least three independent pathways (protein kinase C, Src or mitogen-activated kinases) but the details are still unknown. Thyroid hormones induce nongenomic effects on at least three important Na(+)-dependent transport systems, the Na(+)/K(+)-ATPase, the Na(+)/H(+) exchanger, and amino acid transport System A, leading to a mitogenic response in embryo cells; but modulation of the same transport systems may have different roles in other cells and at different developmental stages. It seems that thyroid hormones in many cases can modulate nongenomically the same targets affected by the nuclear receptors through long-term mechanisms. Recent results on nongenomic effects confirm the old theory that the primary role of thyroid hormones is to keep the steady-state level of functioning of the cell, but more and more mechanisms are discovered by which this goal can be achieved.

Plasma and urine betaine and dimethylglycine variation in healthy young male subjects

OBJECTIVES

We aimed to compare the individuality (within subject consistency) of plasma and urine betaine and N,N-dimethylglycine.

DESIGN AND METHODS

In two separate groups of 8 males (ages 19 to 40), plasma (10) and urine (6) samples were collected either over a single day or over an 8 week period. The individuality of the betaine and N,N-dimethylglycine plasma concentrations and excretions were estimated by one-way repeated measures analysis of variance. The reliability coefficients and indices of individuality were calculated. The between-subject variation in the study population was compared with that in a normal population (n=192 for plasma, 205 for urine).

RESULTS

Plasma betaine concentrations were significantly different between subjects over 24 h and 8 weeks (p<0.00001). Plasma dimethylglycine concentrations were different over 24 h. Urine betaine and dimethylglycine excretions were different in both (p<0.0001). Betaine was more individual than dimethylglycine in both plasma and urine. Compared with a normal healthy population, the between-subject variation in plasma betaine was less (p<0.001) in the study group, but similar for dimethylglycine and for urine betaine.

CONCLUSIONS

Plasma betaine and urinary betaine excretions are more individual than dimethylglycine. Plasma and urine betaine are highly individual in the general population.

Discovery of sarcosine dimethylglycine methyltransferase from Galdieria sulphuraria

An enzyme with sarcosine dimethylglycine methyltransferase (SDMT) activity has been identified in the thermophilic eukaryote, Galdieria sulphuraria. The crystal structure of the enzyme, solved to a resolution of 1.95 A, revealed a fold highly similar to that of mycolic acid synthases. The kcat and apparent K(M) values were 64.3 min(-1) and 2.0 mM for sarcosine and 85.6 min(-1) and 2.8 mM for dimethylglycine, respectively. Apparent K(M) values of S-adenosylmethionine were 144 and 150 microM for sarcosine and dimethylglycine, respectively, and the enzyme melting temperature was 61.1 degrees C. Modeling of cofactor binding in the active site based on the structure of methoxy mycolic acid synthase 2 revealed a number of conserved interactions within the active site.

Ionic determinants of pH of acidic compartments under hypertonic conditions in trout hepatocytes

Exposure of trout hepatocytes to hypertonicity induced a decrease in acridine orange (AO) fluorescence, indicating a corresponding decrease in pH inside the lumen of acidic compartments (pH(L)). Pre-exposure of cells to the specific V-ATPase inhibitor bafilomycin A1 (0.3 micromol l(-1)) increased AO fluorescence - unmasking H(+) leaks under steady-state conditions - and partially removed the hypertonicity-induced pH(L) decrease. The sustainability of the luminal acidification, but not the acidification itself, appeared to depend on a low K(+) and a high Cl(-) conductance under hypertonic conditions. Increasing K(+) conductance using the specific ionophore valinomycin (10 micromol l(-1)) or removal of extracellular Cl(-) after an instant drop in AO fluorescence resulted in a reversal of luminal acidity. The alkalinization measured under hypertonic conditions in the absence of Cl(-) was largely attenuated when cells were bathed in HCO(3)(-)-free medium, signifying the possible presence of Cl(-)/HCO(3)(-) exchange. Under steady-state conditions, while a slight and brief pH(L) increase was measured upon exposure of cells to valinomycin, Cl(-) removal, unexpectedly, induced a decrease in pH(L), indicating a role for extracellular Cl(-) in limiting luminal acidification. This was confirmed by the substantial pH(L) decrease measured upon exposure of cells to the anion exchanger inhibitor SITS (0.5 mmol l(-1)). Furthermore, hypertonicity-induced acidification was still noticeable in the presence of SITS. On the other hand, the hypertonicity-induced acidification was significantly reduced in the absence of extracellular Na(+) or Ca(2+). However, BAPTA-AM induced an increase in steady-state pH(L) that was independent of V-ATPase inhibition. Moreover, the BAPTA-induced alkalinization was still apparent after depletion of intracellular Ca(2+) using the Ca(2+) ionophore A23187 in Ca(2+)-free medium. We conclude that pH(L) of trout hepatocytes is sensitive to hypertonicity and ionic determinants of hypertonicity. Thus, changes in pH(L) should be considered when studying pH adaptations to hypertonic stress.

The nucleolus exhibits an osmotically regulated gatekeeping activity that controls the spatial dynamics and functions of nucleolin

We demonstrate that physiologically relevant perturbations in the osmotic environment rheostatically regulate a gatekeeping function for the nucleolus that controls the spatial dynamics and functions of nucleolin. HeLa cells and U2-OS osteosarcoma cells were osmotically challenged with 100-200 mm sorbitol, and the intranuclear distribution of nucleolin was monitored by confocal microscopy. Nucleolin that normally resides in the innermost fibrillar core of the nucleolus, where it assists rDNA transcription and replication, was expelled within 30 min of sorbitol addition. The nucleolin was transferred into the nucleoplasm, but it distributed there non-uniformly; locally high levels accumulated in 4',6-diamidino-2-phenylindole-negative zones containing euchromatic (transcriptionally active) DNA. Inositol pyrophosphates also responded within 30 min of hyperosmotic stress: levels of bisdiphosphoinositol tetrakisphosphate increased 6-fold, and this was matched by decreased levels of its precursor, diphosphoinositol pentakisphosphate. Such fluctuations in inositol pyrophosphate levels are of considerable interest, because, according to previously published in vitro data, they regulate the degree of phosphorylation of nucleolin through a novel kinase-independent phosphotransferase reaction ( Saiardi, A., Bhandari, A., Resnick, R., Cain, A., Snowman, A. M., and Snyder, S. H. (2004) Science 306, 2101-2105 ). However, by pharmacologically intervening in inositol pyrophosphate metabolism, we found that it did not supervise the osmotically driven switch in the biological activities of nucleolin in vivo.

Biochemistry of oxidative stress

The terms 'antioxidant', 'oxidative stress' and 'oxidative damage' are widely used but rarely defined. This brief review attempts to define them and to examine the ways in which oxidative stress and oxidative damage can affect cell behaviour both in vivo and in cell culture, using cancer as an example.

Sex differences in the control of plasma concentrations and urinary excretion of glycine betaine in patients attending a lipid disorders clinic

OBJECTIVES

To find whether the control of betaine metabolism differs between male and female patients and identify the effects of insulin and other hormones.

DESIGN AND METHODS

Data from non-diabetic lipid clinic patients (82 female symbol and 76 male symbol) were re-analyzed by sex. Data on insulin, thyroid hormones and leptin were included in models to identify factors affecting the circulation and excretion of betaine and its metabolites.

RESULTS

Different factors influenced plasma concentrations and urinary excretion of betaine, dimethylglycine and homocysteine in males and females. In males, apolipoprotein B (negative), thyroid stimulating hormone (positive) and insulin (negative) predicted circulating betaine, consistent with betaine-homocysteine methyltransferase mediated control. In females, insulin positively predicted plasma dimethylglycine. Urinary betaine excretion positively predicted circulating homocysteine in males (p<0.001), whereas dimethylglycine excretion (also indicating betaine loss) was a stronger positive predictor (p<0.001) in females. Carnitine affected betaine homeostasis.

CONCLUSIONS

Betaine metabolism is under endocrine control, and studies should use sex stratified groups.

Purification, sequencing, and molecular identification of a mammalian PP-InsP5 kinase that is activated when cells are exposed to hyperosmotic stress

Mammalian cells utilize multiple signaling mechanisms to protect against the osmotic stress that accompanies plasma membrane ion transport, solute uptake, and turnover of protein and carbohydrates (Schliess, F., and Haussinger, D. (2002) Biol. Chem. 383, 577-583). Recently, osmotic stress was found to increase synthesis of bisdiphosphoinositol tetrakisphosphate ((PP)2-InsP4), a high energy inositol pyrophosphate (Pesesse, X., Choi, K., Zhang, T., and Shears, S. B. (2004) J. Biol. Chem. 279, 43378-43381). Here, we describe the purification from rat brain of a diphosphoinositol pentakisphosphate kinase (PPIP5K) that synthesizes (PP)2-InsP4. Partial amino acid sequence, obtained by mass spectrometry, matched the sequence of a 160-kDa rat protein containing a putative ATP-grasp kinase domain. BLAST searches uncovered two human isoforms (PPIP5K1 (160 kDa) and PPIP5K2 (138 kDa)). Recombinant human PPIP5K1, expressed in Escherichia coli, was found to phosphorylate diphosphoinositol pentakisphosphate (PP-InsP5) to (PP)2-InsP4 (Vmax = 8.3 nmol/mg of protein/min; Km = 0.34 microM). Overexpression in human embryonic kidney cells of either PPIP5K1 or PPIP5K2 substantially increased levels of (PP)2-InsP4, whereas overexpression of a catalytically dead PPIP5K1(D332A) mutant had no effect. PPIP5K1 and PPIP5K2 were more active against PP-InsP5 than InsP6, both in vitro and in vivo. Analysis by confocal immunofluorescence showed PPIP5K1 to be distributed throughout the cytoplasm but excluded from the nucleus. Immunopurification of overexpressed PPIP5K1 from osmotically stressed HEK cells (0.2 M sorbitol; 30 min) revealed a persistent, 3.9 +/- 0.4-fold activation when compared with control cells. PPIP5Ks are likely to be important signaling enzymes.

An abnormal urinary excretion of glycine betaine may persist for years

OBJECTIVES

Does abnormal betaine excretion persist?

DESIGN AND METHODS

Patients (10) with abnormal excretion in 1998 were recalled in 2005. Subsequent urine samples were collected on 4 days from persistently abnormal subjects.

RESULTS

Half the 1998 abnormal patients were abnormal in 2005. Only 1/20 controls was abnormal (p=0.015). All patients with abnormal excretion in 1998 and 2005 had abnormal excretion on successive days while no controls did.

CONCLUSIONS

High betaine excretion may be chronic and a health risk.

Extracellular glutamine is a critical modulator for regulatory volume increase in human glioma cells

Mammalian cells regulate their volume to prevent unintentional changes in intracellular signaling, cell metabolism, and DNA integrity. Intentional cell volume changes occur as cells undergo proliferation, apoptosis, or cell migration. To regulate cell volume, cells use channels and transport systems to flux osmolytes across the plasma membrane followed by the obligatory movement of water. While essentially all cells are capable of regulatory volume decrease (RVD), regulatory volume increase (RVI) mechanisms have only been reported in some cell types. In this investigation, we used human glioma cells as a model system to determine conditions necessary for RVI. When exposed to hyperosmotic conditions through the addition of 30 mosM NaCl or sucrose, D54-MG and U251 glioma cell lines and glioma cells from acute patient biopsies shrunk transiently but were able to fully recover their original cell volume within 40-70 min. This ability was highly temperature sensitive and absolutely required the presence of low millimolar concentrations of l-glutamine in the extracellular solution. Other known substrates of glutamine transporters such as methyl-amino isobutyric acid (MeAIB), alanine, and threonine were unable to support RVI. The ability of cells to undergo RVI also required the presence of Na+, K+, and Cl- and was inhibited by the NKCC inhibitor, bumetanide, consistent with the involvement of a Na+/K+/2Cl- cotransporter (NKCC). Moreover, the expression of NKCC1 was demonstrated by Western blot. We concluded that regulatory volume increase in human glioma cells occurs through the uptake of Na+, K+, and Cl- by NKCC1 and is modulated by the presence of glutamine.

Inter- and intra-individual variations in normal urinary glycine betaine excretion

OBJECTIVES

To establish whether normal human subjects excrete glycine betaine at a constant rate.

DESIGN AND METHODS

Urine was collected from ten normal healthy male subjects for 14 days, during which fluid intake was systematically varied from <800 mL to >3 L per day. Glycine betaine, sorbitol and creatinine excretions were estimated per day and as millimole per mol creatinine.

RESULTS

The intrasubject SD of urine glycine betaine was 3.5 mmol/mol creatinine, and the intersubject SD 5.8 mmol/mol creatinine. The intrasubject SD of plasma glycine betaine was 10.2 mol/L and the intersubject SD 14.2 mol/L. Water load had little effect on glycine betaine excretion and plasma glycine betaine. After 12 years, excretions and plasma concentrations tended to parallel the initial results.

CONCLUSIONS

Normal subjects have consistent individual glycine betaine excretions that are not strongly influenced by urine volume. Abnormal excretions, or significant changes in excretion, can be interpreted as indicating a pathological process.

CD95 activation in the liver: ion fluxes and oxidative signaling

Apoptosis is characterized by typical features as cell shrinkage, nuclear condensation, DNA fragmentation, and apoptotic body formation. Whereas some signs of apoptosis are cell type-and death signal-dependent, apoptotic cell volume decrease is an early and ubiquitous event and little is known about the signalling events, which are localized upstream of the plasma membrane transport steps leading to apoptotic cell volume decrease and the proapoptotic events, which are induced by osmolyte loss and cell shrinkage. Ion fluxes and oxidative signaling were recently shown to play an important role in signal transduction with respect to apoptotic cell death within the liver, as a ceramide-dependent activation of the NADPH oxidase was identified as the source of reactive oxygen species generation in rat hepatocytes upon treatment with CD95 ligand, hydrophobic bile salts or hyperosmolarity. The NADPH oxidase-derived ROS signal then allows via Yes, JNK, and EGFR activation for CD95 tyrosine phosphorylation as a prerequisite for CD95 targeting to the plasma membrane and formation of the death inducing signalling complex. Other covalent modifications such as CD95-tyrosine-nitration or CD95-serine/threonine-phosphorylation can interfere with the CD95 activation process. The findings not only provide a mechanistic explanation for the high susceptibility of dehydrated cells for apoptosis, but also give insight into the role of ion fluxes and oxidative signaling with respect to apoptotic cell death within the liver.

Glutamine: a Trojan horse in ammonia neurotoxicity

Mechanisms involved in hepatic encephalopathy still remain to be defined. Nonetheless, it is well recognized that ammonia is a major factor in its pathogenesis, and that the astrocyte represents a major target of its CNS toxicity. In vivo and in vitro studies have shown that ammonia evokes oxidative/nitrosative stress, mitochondrial abnormalities (the mitochondrial permeability transition, MPT) and astrocyte swelling, a major component of the brain edema associated with fulminant hepatic failure. How ammonia brings about these changes in astrocytes is not well understood. It has long been accepted that the conversion of glutamate to glutamine, catalyzed by glutamine synthetase, a cytoplasmic enzyme largely localized to astrocytes in brain, represented the principal means of cerebral ammonia detoxification. Yet, the "benign" aspect of glutamine synthesis has been questioned. This article highlights evidence that, at elevated levels, glutamine is indeed a noxious agent. We also propose a mechanism by which glutamine executes its toxic effects in astrocytes, the "Trojan horse" hypothesis. Much of the newly synthesized glutamine is subsequently metabolized in mitochondria by phosphate-activated glutaminase, yielding glutamate and ammonia. In this manner, glutamine (the Trojan horse) is transported in excess from the cytoplasm to mitochondria serving as a carrier of ammonia. We propose that it is the glutamine-derived ammonia within mitochondria that interferes with mitochondrial function giving rise to excessive production of free radicals and induction of the MPT, two phenomena known to bring about astrocyte dysfunction, including cell swelling. Future therapeutic approaches might include controlling excessive transport of newly synthesized glutamine to mitochondria and its subsequent hydrolysis.

Endosomal Acidification and Activation of NADPH Oxidase Isoforms Are Upstream Events in Hyperosmolarity-induced Hepatocyte Apoptosis

Hyperosmotic exposure of rat hepatocytes induced a rapid oxidative-stress(ROS) response as an upstream signal for proapoptotic CD95 activation. This study shows that hyperosmotic ROS formation involves a rapid ceramide- and protein kinase Czeta (PKCzeta)-dependent serine phosphorylation of p47phox and subsequent activation of NADPH oxidase isoforms. Hyperosmotic p47phox phosphorylation and ROS formation were sensitive to inhibition of sphingomyelinases and were strongly blunted after knockdown of acidic sphingomyelinase (ASM) or of p47phox protein. Hyperosmolarity induced a rapid bafilomycin- and 4,4 '-diisothiocyanostilbene-2,2 '-disulfonic acid disodium salt (DIDS)-sensitive acidification of a vesicular compartment, which was accessible to endocytosed fluorescein isothiocyanate-dextran and colocalized with ASM, PKCzeta, and the NADPH oxidase isoform Nox 2 (gp91phox). Bafilomycin and DIDS prevented the hyperosmolarity-induced increase in ceramide formation, p47phox phosphorylation, and ROS formation. As shown recently (Reinehr, R., Becker, S., Höngen, A., and Häussinger, D. (2004) J. Biol. Chem. 279, 23977-23987), hyperosmolarity induced a Yes-dependent activation of JNK and the epidermal growth factor receptor (EGFR), followed by EGFR-CD95 association, EGFR-catalyzed CD95-tyrosine phosphorylation, and translocation of the EGFR-CD95 complex to the plasma membrane, where formation of the deathinducing signaling complex occurs. These proapoptotic responses were not only sensitive to inhibitors of sphingomyelinase, PKCzeta, or NADPH oxidases but also to ASM knockdown, bafilomycin, and DIDS, i.e. maneuvers largely preventing hyperosmolarity-induced endosomal acidification and/or ceramide formation. In hepatocytes from p47phox knock-out mice, hyperosmolarity failed to activate the CD95 system. The data suggest that hyperosmolarity induces endosomal acidification as an important upstream event for CD95 activation through stimulation of ASM-dependent ceramide formation and activation of NADPH oxidase isoforms.

Hyperosmotic activation of the CD95 death receptor system

Apoptosis is characterized by cell shrinkage, nuclear condensation, DNA fragmentation and apoptotic body formation. These features distinguish apoptosis from other types of cell death, such as necrosis. Whereas some signs of apoptosis, such as externalization of phosphatidylserine, altered mitochondrial function or activation of caspases are cell type- and death signal-dependent, apoptotic cell volume decrease (AVD) is an early and ubiquitous event and little is known about the signalling events, which are localized upstream of the plasma membrane transport steps leading to AVD and the proapoptotic events, which are induced by osmolyte loss and cell shrinkage. In hepatocytes hyperosmotic shrinkage sensitizes the cells towards CD95 ligand-induced apoptosis by activating the CD95 system. This complex process with a NADPH oxidase-derived reactive oxygen species signal as an important upstream event, allows via Yes, JNK and epidermal growth factor-receptor activation for CD95 tyrosine phosphorylation as a prerequisite for CD95 targeting to the plasma membrane and formation of the death inducing signalling complex. Other covalent modifications such as CD95-tyrosine-nitration or CD95-serine/threonine-phosphorylation can interfere with the CD95 activation process. The findings not only provide a mechanistic explanation for the high susceptibility of dehydrated cells for apoptosis, but also give insight into the role of AVD.