Neural responses to oral administration of erythritol vs. sucrose and sucralose explain differences in subjective liking ratings.

INTRODUCTION: High sugar intake is associated with many chronic diseases. However, non-caloric sweeteners (NCSs) might fail to successfully replace sucrose due to the mismatch between their rewarding sweet taste and lack of caloric content. The natural NCS erythritol has been proposed as a sugar substitute due to its satiating properties despite being non-caloric. We aimed to compare brain responses to erythritol vs. sucrose and the artificial NCS sucralose in a priori taste, homeostatic, and reward brain regions of interest (ROIs). METHODS: We performed a within-subject, single-blind, counterbalanced fMRI study in 30 healthy men (mean ± SEM age:24.3 ± 0.8 years, BMI:22.3 ± 0.3 kg/m2). Before scanning, we individually matched the concentrations of both NCSs to the perceived sweetness intensity of a 10% sucrose solution. During scanning, participants received 1 mL sips of the individually titrated equisweet solutions of sucrose, erythritol, and sucralose, as well as water. After each sip, they rated subjective sweetness liking. RESULTS: Liking ratings were significantly higher for sucrose and sucralose vs. erythritol (both pHolm = 0.0037); water ratings were neutral. General Linear Model (GLM) analyses of brain blood oxygen level-depended (BOLD) responses at qFDR<0.05 showed no differences between any of the sweeteners in a priori ROIs, but distinct differences were found between the individual sweeteners and water. These results were confirmed by Bayesian GLM and machine learning-based models. However, several brain response patterns mediating the differences in liking ratings between the sweeteners were found in whole-brain multivariate mediation analyses. Both subjective and neural responses showed large inter-subject variability. CONCLUSION: We found lower liking ratings in response to oral administration of erythritol vs. sucrose and sucralose, but no differences in neural responses between any of the sweeteners in a priori ROIs. However, differences in liking ratings between erythritol vs. sucrose or sucralose are mediated by multiple whole-brain response patterns.

Erythritol Can Inhibit the Expression of Senescence Molecules in Mouse Gingival Tissues and Human Gingival Fibroblasts.

Oral aging causes conditions including periodontal disease. We investigated how the sugar alcohol erythritol, which has anti-caries effects, impacts aging periodontal tissues and gingival fibroblasts in mice and humans in vivo and in vitro. Mice were classified into three groups: control groups of six-week-old (YC) and eighteen-month-old mice (AC) and a group receiving 5% w/w erythritol water for 6 months (AE). After rearing, RNA was extracted from the gingiva, and the levels of aging-related molecules were measured using PCR. Immunostaining was performed for the aging markers p21, γH2AX, and NF-κB p65. p16, p21, γH2AX, IL-1ß, and TNFα mRNA expression levels were higher in the gingiva of the AC group than in the YC group, while this enhanced expression was significantly suppressed in AE gingiva. NF-κB p65 expression was high in the AC group but was strongly suppressed in the AE group. We induced senescence in cultured human gingival fibroblasts using H2O2 and lipopolysaccharide before erythritol treatment, which reduced elevated senescence-related marker (p16, p21, SA-ß-gal, IL-1ß, and TNFα) expression levels. Knockdown of PFK or PGAM promoted p16 and p21 mRNA expression, but erythritol subsequently rescued pyruvate production. Overall, intraoral erythritol administration may prevent age-related oral mucosal diseases.

Evaluation of Solutions Containing Fluoride, Sodium Trimetaphosphate, Xylitol, and Erythritol, Alone or in Different Associations, on Dual-Species Biofilms.

Although the association of polyols/polyphosphates/fluoride has been demonstrated to promote remarkable effects on dental enamel, little is known on their combined effects on biofilms. This study assessed the effects of solutions containing fluoride/sodium trimetaphosphate (TMP)/xylitol/erythritol on dual-species biofilms of Streptococcus mutans and Candida albicans. Biofilms were grown in the continuous presence of these actives alone or in different associations. Quantification of viable plate counts, metabolic activity, biofilm biomass, and extracellular matrix components were evaluated. Overall, fluoride and TMP were the main actives that significantly influenced most of the variables analyzed, with a synergistic effect between them for S. mutans CFUs, biofilm biomass, and protein content of the extracellular matrix (p < 0.05). A similar trend was observed for biofilm metabolic activity and carbohydrate concentrations of the extracellular matrix, although without statistical significance. Regarding the polyols, despite their modest effects on most of the parameters analyzed when administered alone, their co-administration with fluoride and TMP led to a greater reduction in S. mutans CFUs and biofilm biomass compared with fluoride alone at the same concentration. It can be concluded that fluoride and TMP act synergistically on important biofilm parameters, and their co-administration with xylitol/erythritol significantly impacts S. mutans CFUs and biomass reduction.

Erythritol modulates the polarization of macrophages: Potential role of tumor necrosis factor-α and Akt pathway.

Low-calorie sweeteners are substitutes for sugar and frequently used by patients with cardiometabolic diseases. Erythritol, a natural low-calorie sugar alcohol, was linked to cardiometabolic diseases in several recent metabolomics studies. However, the characterization of its role in disease development is lacking. Macrophage polarization orchestrates the immune response in various inflammatory conditions, most notably cardiometabolic disease. Therefore, the physiological effects of Erythritol on THP-1 macrophages were investigated. We observed an increased cellular abundance of proinflammatory M1 macrophages, characterized by CD11c, TNF-α, CD64, CD38, and HLA-DR markers and decreased anti-inflammatory M2 macrophages, characterized by mannose receptor CD206. The, Erythritol increased ROS generation, and the activation of the AKT pathway, cytosolic calcium overload, and cell cycle arrest at the G1 phase. Concomitantly, an increased population of necroptotic macrophages was observed. In conclusion, we provide evidence that Erythritol induced the proinflammatory phenotype in THP-1 macrophages and this was associated with an increased population of necroptotic macrophages. PRACTICAL APPLICATIONS: This assessment provides evidence of the effects of Erythritol on macrophages, particularly THP-1-derived macrophages. Our results support the role of Erythritol in driving the inflammation that is associated with cardiometabolic diseases and provide insights in the role of Erythritol as an inducer of necroptosis in THP-1 derived macrophages that could be associated the disease.

Atividade antimicrobiana de Stevia rebaudiana Bertoni e de adoçantes não calóricos sobre bactérias cariogênicas: estudo in vitro / Antimicrobial activity of Stevia rebaudiana Bertoni and non-caloric sweeteners on cariogenic bacteria: in vitro study

Objetivo: avaliar a atividade antimicrobiana in vitro da planta Stevia rebaudiana Bertoni e de adoçantes não calóricos sobre o crescimento de Streptococcus mutanse Lactobacillus casei, micro-organismos cariogênicos presentes na cavidade bucal. Materiais e método: o estudo foi realizado utilizando as cepas padrões de S.mutans (UA159) e L. casei (ATCC7469). Foram avaliados diferentes compostos não calóricos substitutos dasacarose nas concentrações de 1%, 5% e 10%: eritritol(ER), Fit Sucralose® (SU), Stevita® (ST), solução de Steviarebaudiana Bertoni (SSr) e, como controle positivo,digluconato de clorexidina (DC). A análise do efeito inibitório desses compostos no crescimento das bactériasfoi feita por meio da técnica de difusão em ágar. Resultado:observou-se que existe um efeito inibitório decrescimento de ambos os micro-organismos por parte da SSr e do ER, enquanto os demais adoçantes testa dosnão tiveram efeito inibitório sobre esses micro-organismos.Conclusão: os resultados demonstram que SSR eER apresentam efeito inibidor no crescimento das cepastestadas de S. mutans e L. casei. (AU)

Objective: The study evaluated the in vitro antimicrobial activity of the Stevia rebaudiana Bertoni plant and non-caloric sweeteners on the growth of Streptococcus mutans and Lactobacillus casei, which are cariogenic microorganisms present in the oral cavity. Materials and method: The study was conducted using the standard strains of S. mutans (UA159) and L. casei (ATCC7469). Different non-caloric compounds were evaluated at concentrations of 1%, 5%, and 10%: erythritol (ER), Fit Sucralose™ (SU), Stevita™ (ST), Stevia rebaudiana Bertoni solution (SSr), and chlorhexidine digluconate (CD) as positive control. The inhibitory effect of these compounds on the growth of bacteria were analyzed by the agar diffusion technique. Result: There was a growth inhibition effect for both microorganisms by SSr and ER, whereas the other sweeteners tested had no inhibitory effect on the microorganisms. Conclusion: The results showed that SSr and ER present an inhibitory effect on the growth the strains tested of S. mutans and L. casei. (AU)

Clinical and laboratory evaluation of the effects of different treatment modalities on titanium healing caps: a randomized, controlled clinical trial.

OBJECTIVES: The objective of this study is to evaluate the effects of treatment modalities on titanium surface characteristics and surrounding tissues. MATERIALS AND METHODS: Eighteen participants each had four titanium healing caps (HC) attached to four newly inserted implants. After healing, each HC was randomly assigned to either (1) titanium curettes (TC), (2) stainless steel ultrasonic tip (PS), (3) erythritol air-polishing powder (EP), or (4) only rubber cup polishing (CON). Probing depths (PD), bleeding on probing (BOP), matrix metalloproteinase 8 (MMP-8), and periopathogens were recorded before and 3 months following instrumentation. After final assessments, HCs were removed, cleaned, and subjected to (a) bacterial colonization (Streptococcus gordonii, 24 h; mixed culture, 24 h) and (b) gingival fibroblasts (5 days). HC surfaces were analyzed with a scanning electron microscope (SEM). RESULTS: No significant differences between the groups were evident before or after instrumentation for PD and BOP (except TC showed a significant decrease in PD; p = 0.049). MMP-8 levels and bacterial loads were always very low. MMP-8 decreased further after instrumentation, while bacteria levels showed no change. No significant differences (p > 0.05) were evident in bacterial colonization or fibroblast attachment. A comparison of the overall mean SEM surface roughness scores showed a significant difference between all groups (p < 0.0001) with the lowest roughness after EP. CONCLUSIONS: All treatments performed yielded comparable outcomes and may be implemented safely. CLINICAL RELEVANCE: Clinicians may fear implant surface damage, but all instrumentation types are safe and non-damaging. They can be implemented as needed upon considering the presence of staining and soft and hard deposits.

Effects of L-carnitine, erythritol and betaine on pro-inflammatory markers in primary human corneal epithelial cells exposed to hyperosmotic stress.

PURPOSE: To explore the effects of osmoprotectants on pro-inflammatory mediator production in primary human corneal epithelial cells (HCECs) exposed to hyperosmotic stress. METHODS: HCECs cultured in iso-osmolar medium (312 mOsM) were switched to hyperosmotic media with or without prior incubation with 2-20 mM of l-carnitine, erythritol or betaine for different time periods. The mRNA expression and protein production of pro-inflammatory markers in HCECs were evaluated by RT-qPCR and ELISA. RESULTS: Hyperosmolar media significantly stimulated the mRNA and protein expression of pro-inflammatory cytokines, TNF-α, IL-1ß and IL-6, and chemokines, IL-8, CCL2 and CCL20 in HCECs in an osmolarity dependent manner. The stimulated expression of these pro-inflammatory mediators was significantly but differentially suppressed by l-carnitine, erythritol or betaine. l-Carnitine displayed the greatest inhibitory effects and down-regulated 54-77% of the stimulated mRNA levels of TNF-α (down from 12.3-5.7 fold), IL-1ß (2.2-0.9 fold), IL-6 (7.3-2.9 fold), IL-8 (4.6-2.0 fold), CCL2 (15.3-3.5 fold) and CCL20 (4.1-1.5 fold) in HCECs exposed to 450 mOsM. The stimulated protein production of TNF-α, IL-1ß, IL-6 and IL-8 was also significantly suppressed by l-carnitine, erythritol and betaine. l-carnitine suppressed 49-79% of the stimulated protein levels of TNF-α (down from 81.3 to 17.4 pg/ml), IL-1ß (56.9-29.2 pg/ml), IL-6 (12.8-4.6 ng/ml) and IL-8 (21.2-10.9 ng/ml) by HCECs exposed to 450 mOsM. Interestingly, hyperosmolarity stimulated increase in mRNA and protein levels of TNF-α, IL-1ß and IL-6 were significantly suppressed by a transient receptor potential vanilloid channel type 1 (TRPV1) activation inhibitor capsazepine. CONCLUSIONS: l-carnitine, erythritol and betaine function as osmoprotectants to suppress inflammatory responses via TRPV1 pathway in HCECs exposed to hyperosmotic stress. Osmoprotectants may have efficacy in reducing innate inflammation in dry eye disease.

Osmoprotectants suppress the production and activity of matrix metalloproteinases induced by hyperosmolarity in primary human corneal epithelial cells.

PURPOSE: Hyperosmolarity has been recognized as a proinflammatory stress in the pathogenesis of dry eye disease. This study investigated the suppressive effect of osmoprotectants (L-carnitine, erythritol, and betaine) on the production and activity of matrix metalloproteinases (MMPs) in primary human corneal epithelial cells (HCECs) exposed to hyperosmotic stress. METHODS: Primary HCECs were established from fresh donor limbal tissue explants. The cultures in iso-osmolar medium (312 mOsM) were switched to hyperosmotic media with or without prior incubation with different concentrations of L-carnitine, erythritol, or betaine (2, 10, or 20 mM). The mRNA expression of the MMPs was determined with reverse transcription and quantitative real-time PCR (RT-qPCR). Protein production and activity were evaluated with immunofluorescent staining and gelatin zymography. RESULTS: Hyperosmotic media (400, 450, or 500 mOsM) significantly stimulated mRNA expression of collagenase MMP-13, gelatinases MMP-9 and MMP-2, stromelysin MMP-3, and matrilysin MMP-7, mostly in an osmolarity-dependent fashion. The stimulated mRNA expression and protein production of these MMPs were significantly but differentially suppressed by L-carnitine, erythritol, or betaine, as evaluated with RT-qPCR and immunofluorescent staining. Interestingly, these osmoprotectants not only suppressed production but also inhibited activation of MMP-9 and MMP-2, as evaluated with gelatin zymography. CONCLUSIONS: Our findings for the first time demonstrate that osmoprotectants, L-carnitine, erythritol, and betaine, suppress the gene expression, protein production, and enzymatic activity of MMPs in HCECs exposed to hyperosmotic stress. L-carnitine appears to have the broadest and strongest suppressive effect on these MMPs. These osmoprotectants may have potential effects in protecting ocular surface epithelia from MMP-mediated disorders in dry eye disease.

2-methyl-L-erythritol glycosides from Gardenia jasminoides.

Two new glycosides, 2-methyl-L-erythritol-4-O-(6-O-trans-sinapoyl)-ß-D-glucopyranoside (1) and 2-methyl-L-erythritol-1-O-(6-O-trans-sinapoyl)-ß-D-glucopyranoside (2), along with two known triterpenoids (3-4), four quinic acid derivatives (5-8) and one flavonoid (9) were isolated from the fruit of Gardenia jasminoides. Their structures were elucidated through MS and 2D NMR experiments (HMQC and HMBC). Inhibitory effects of the isolated compounds on nitric oxide production in lipopolysaccharide-activated macrophages were evaluated. Though 2-methyl-D-erythritol and its glycosides have been reported in a few references, this is the first report about 2-methyl-L-erythritol glycosides. Based on this finding, we propose that 2-methyl-L-erythritol might be a new intermediate in the non-mevalonate biosynthesis of terpenoids.

Effect of exogenous erythritol on growth and survival of Brucella.

Erythritol has been considered as an important factor for the pathogenesis of Brucella abortus 2308 and its ability to cause abortion in ruminants. There is a lack of laboratory models to study the Brucella-erythritol relationship, as commonly used murine models do not have erythritol. We tested the effect of exogenous erythritol on the growth of Brucella in iron minimal medium (IMM), in infected macrophage culture and in infected mice to determine if these models can be used to study the relationship between Brucella and erythritol. An effect of erythritol on Brucella growth was only seen in IMM. There appear to be no effect of erythritol on Brucella growth in macrophage cell cultures or in mice. This shows that administration of erythritol to the mice or macrophages cannot mimic the environment in ruminants during pregnancy and thus cannot be used as models to understand the effect of erythritol on Brucella pathogenesis.

Biosurfactant mannosyl-erythritol lipid inhibits secretion of inflammatory mediators from RBL-2H3 cells.

BACKGROUND: Biosurfactant mannosyl-erythritol lipids (MELs) are glycolipids produced by microbes that have various biological activities. It has been reported that MELs exhibit excellent surface-activity and also various bioactivities, such as induction of cell differentiation and apoptosis. However, little is known about their action related to drug discovery or drug seeds. METHODS: We investigated the effects of MELs on the secretion of inflammatory mediators from mast cells that play a central role in allergic responses. Mast cells secrete three kinds of inflammatory mediators and we quantified these secreted mediators by photometer or ELISA. The action mechanisms of MELs were studied by Ca(2+)-sensitive fluorescence dye and Western blotting of phosphorylated proteins. RESULTS: MELs inhibited exocytotic release by antigen stimulation in a dose-dependent manner. We also found that MELs inhibited antigen-induced secretion of leukotriene C(4) and cytokine TNF-α (tumor necrosis factor-α). The inhibitory action of MELs on mediator secretion was mediated by inhibition of Ca(2+) increase, phosphorylation of MAP kinases and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) that serve as a molecular machinery for exocytotic membrane fusion. CONCLUSIONS: MELs have anti-inflammatory action inhibiting the secretion of inflammatory mediators from mast cells. GENERAL SIGNIFICANCE: MELs affects two of major intracellular signaling pathways including Ca(2+) increase and MAP kinases. MELs also inhibited the phosphorylation of SNARE proteins that is crucial for not only exocytosis but also intracellular vesicular trafficking.

K+-independent initiation of motility in chum salmon sperm treated with an organic alcohol, glycerol.

Sperm of salmonid fishes are quiescent in the presence of millimolar concentrations of extracellular K+, but motility initiation occurs when sperm are suspended in K+-free medium. In this study, glycerol (CH2OHCHOHCH2OH) treatment of intact sperm in the presence of K+ induced the initiation of motility even though a large amount of K+ was present. Another organic alcohol, erythritol (CH2OH(CHOH)2CH2OH), had a similar effect, but ethylene glycol (CH2OHCH2OH) did not initiate sperm motility. Furthermore, this glycerol-treated sperm showed motility without subsequent addition of ATP and cAMP. CCCP, an uncoupler of the mitochondrial electron-transport chain involved in ATP synthesis, suppressed motility of glycerol-treated sperm, suggesting that ATP synthesis is required for dynein to slide microtubules in glycerol-treated sperm. The amount of intracellular cAMP ([cAMP]i) in glycerol-treated sperm did not increase on motility activation, but a protein kinase A (PKA) inhibitor, H-89, inhibited glycerol-treated sperm motility. In addition, phosphorylation of protein associated with motility initiation also occurred in glycerol-treated sperm, suggesting that the glycerol treatment induces activation of PKA without an increase in [cAMP]i. Taken together, it can be concluded that organic alcohol, glycerol and erythritol induce phosphorylation for motility initiation, bypassing the increase in [cAMP]i as a result of a decrease in extracellular K+ concentration.

Production of the siderophore 2,3-dihydroxybenzoic acid is required for wild-type growth of Brucella abortus in the presence of erythritol under low-iron conditions in vitro.

Production of the siderophore 2,3-dihyroxybenzoic acid (2,3-DHBA) is required for the wild-type virulence of Brucella abortus in cattle. A possible explanation for this requirement was uncovered when it was determined that a B. abortus dhbC mutant (BHB1) defective in 2,3-DHBA production displays marked growth restriction in comparison to its parent strain, B. abortus 2308, when cultured in the presence of erythritol under low-iron conditions. This phenotype is not displayed when these strains are cultured under low-iron conditions in the presence of other readily utilizable carbon and energy sources. The addition of either exogenous 2,3-DHBA or FeCl(3) relieves this growth defect, suggesting that the inability of the B. abortus dhbC mutant to display wild-type growth in the presence of erythritol under iron-limiting conditions is due to a defect in iron acquisition. Restoring 2,3-DHBA production to the B. abortus dhbC mutant by genetic complementation abolished the erythritol-specific growth defect exhibited by this strain in low-iron medium, verifying the relationship between 2,3-DHBA production and efficient growth in the presence of erythritol under low-iron conditions. The positive correlation between 2,3-DHBA production and growth in the presence of erythritol was further substantiated by the observation that the addition of erythritol to low-iron cultures of B. abortus 2308 stimulated the production of 2,3-DHBA by increasing the transcription of the dhbCEBA operon. Correspondingly, the level of exogenous iron needed to repress dhbCEBA expression in B. abortus 2308 was also greater when this strain was cultured in the presence of erythritol than that required when it was cultured in the presence of any of the other readily utilizable carbon and energy sources tested. The tissues of the bovine reproductive tract are rich in erythritol during the latter stages of pregnancy, and the ability to metabolize erythritol is thought to be important to the virulence of B. abortus in pregnant ruminants. Consequently, the experimental findings presented here offer a plausible explanation for the attenuation of the B. abortus 2,3-DHBA-deficient mutant BHB1 in pregnant ruminants.

Functional expression and characterization of EryA, the erythritol kinase of Brucella abortus, and enzymatic synthesis of L-erythritol-4-phosphate.

The eryA gene of the bacterial pathogen Brucella abortus has been functionally expressed in Escherichia coli. The resultant EryA was shown to catalyze the ATP-dependent conversion of erythritol to L-erythritol-4-phosphate (L-E4P). The steady state kinetic parameters of this reaction were determined and the enzyme was used to prepare L-E4P which was shown to be a weak inhibitor of 2-C-methyl-D-erythritol-4-phosphate cytidyltransferase (YgbP).

Mannosylerythritol lipid induces characteristics of neuronal differentiation in PC12 cells through an ERK-related signal cascade.

Rat pheochromocytoma PC12 cells undergo neuronal differentiation in response to nerve growth factor (NGF). The differentiation involves protein kinase cascades that include the kinases MEK and ERK, as well as activation of the transcription factors c-Jun and c-Fos. We show here, that exposure of PC12 cells to mannosylerythritol lipid (MEL), a yeast extracellular glycolipid, enhances the activity of acetylcholinesterase and interrupts the cell cycle at the G1 phase, with resulting outgrowth of neurites and partial cellular differentiation. Treatment with MEL stimulates the phosphorylation of ERK to a similar extent as treatment with NGF, although, the appearance of phosphorylated ERK is somewhat delayed. Both the MEL-induced outgrowth of neurites and the increase in the activity of acetylcholinesterase are prevented by PD98059, a specific inhibitor of MEK. Northern blotting analysis of c-jun transcripts and analysis of transcription in PC12 cells of a c-jun/CAT reporter construct demonstrated a significant increase in the rate of transcription of the c-jun gene upon treatment with MEL. The sequence elements required for the MEL-mediated activation of transcription of the c-jun gene are located between nucleotides -126 and -79 in the 5' flanking region. Our results suggest that MEL induces characteristics of neuronal differentiation in PC12 cells, with transactivation of the c-jun gene, via an ERK-related signal cascade that is partially overlapping the pathways activated in response to NGF. These results might provide the groundwork for the use of microbial extracellular glycolipids as novel reagents for the treatment of cancer cells.

[Effect of antiseptics and redox-cycling agents on Corynebacterium ammoniagenes and related microorganisms in relation to synthesis of a new macroergic compound]. / Deistvie antisepticheskikh sredstv i redokstsikliruiushchikh agentov na Corynebacterium ammoniagenes i rodstvennye mikroorganizmy v sviazi s sintezom novogo makroérga.

Sublethal concentration of the antiseptic composition Desoxon-1 was shown to provoke in cells of Corinebacterium ammoniagenes in a liquid medium the biosynthesis and accumulation of a novel macroergic 2-methylbutane-1,2,3,4-tetraol-2,4-cyclopyrophosphate. This substance is also synthesized when C. ammoniagenes is cultivated in a solid agar medium supplemented with benzylviologen. Cells preloaded with the new cyclopyrophosphate maintain its content when treated with 4% phenol, DP-2, Desoxon-1 or boiled and heated in an autoclave. Experiments with Mycobacterium tuberculosis and BCG revealed the ability of these bacteria to grow in a medium supplemented with BV++ possibly due to ability of synthesis of a new cyclopyrophosphate which was shown to correlate with resistance toward redox-cycling drugs. Accumulation of polyphosphates in the control cells of M. tuberculosis was illustrated by 31P-NMR spectroscopy and disappearance of the polyphosphates during cultivation in a BV(++)-supplemented medium. No signal of the new cyclopyrophosphate was yet registered in cells of M. tuberculosis by 31P-NMR.

Effect of cyclosporine and steroids on canine bile flow.

Cyclosporine and hydrocortisone are the main immunosuppressants used in transplant surgery. The purpose of this study was to determine the effect of intravenous administration of cyclosporine and hydrocortisone on bile flow in dogs. Cyclosporine in doses of 0.5, 1.0 and 1.5 mg.kg-1.hr-1 were administered along with 18 mumol/min intravenous sodium taurocholate to dogs with chronic biliary and gastric fistulas. Bile volume and bile chloride concentration and output were increased by cyclosporine in a dose-related manner, whereas bile salt concentration decreased and bile salt output was unchanged. Hydrocortisone produced small but significant increases in bile flow only at the highest dose of hydrocortisone administered. Subsequently, experiments were performed when sodium taurocholate was administered in progressively increasing doses (9, 18 and 36 mumol/min), with the dose changed every hour. Bile volume, [14C]erythritol clearance in bile and bile salt concentrations were measured with and without cyclosporine and hydrocortisone administration. Cyclosporine increased the bile salt-independent fraction of canalicular bile flow and ductular bile flow. Experiments evaluating the role of the cyclosporine carrier polyoxyethylated castor oil (Cremophor EL) demonstrated that this substance had no independent choleretic activity, whereas cyclosporine dissolved in ethanol and administered without Cremophor EL significantly increased bile flow. The results of this study indicate that cyclosporine stimulates chloride-rich choleresis independent of bile salt secretion.

Cytotoxicity of hyperthermia combined with bleomycin or cis-platinum in cultured RIF cells: modification by thermotolerance and by polyhydroxy compounds.

The effect of thermotolerance and of polyhydroxy compounds on the cytotoxicity of bleomycin and cis-platinum was studied in cultured RIF tumor cells. Cell survival in response to drug-heat treatments was compared in cells not previously exposed to hyperthermia and in preheated cells that had developed thermotolerance. Since cellular accumulation of polyhydroxy compounds is a potential mechanistic basis of thermotolerance, we also compared cell survival of thermotolerant cells and chemically heat-protected cells. The cytotoxicity of bleomycin and cis-platinum in control cells treated with drug plus heat (43 degrees C, 1 h) was increased synergistically over the cytotoxicity of drug and heat alone. In thermotolerant cells, the synergistic interaction was largely reversed with the bleomycin-heat combination but retained with cis-platinum at 43 degrees C. In the absence of heat, bleomycin and cis-platinum showed similar cytotoxicity in control and thermotolerant cells. The addition of heat protectors (erythritol or galactose) modified the drug-heat cytotoxicity similar to thermotolerance. The synergistic interaction of bleomycin-43 degrees C, but not cis-platinum-43 degrees C, was reversed by the polyhydroxy compounds.

Protection against heat-induced cell killing by polyols in vitro.

The polyols erythritol and adonitol reduced 45 degrees heat killing in asynchronous Chinese hamster ovary cells. Heat protection by glycerol and erythritol increased with the apparent intracellular concentration, as inferred from cell volume measurements, and the number of hydroxyl groups per alcohol molecule. The nonlinear tetrahydroxy alcohol pentaerythritol did not protect but sensitized to heat killing. On cell survival curves, the reduced cell killing of protected cells was expressed by an increased Do for the pentahydroxy alcohol adonitol (0.3 M), whereas equimolar concentrations of glycerol increased primarily the Dq (quasithreshold dose) with little increase in Do. The distribution of Chinese hamster ovary cells within the cell cycle was unaffected by the presence of 0.3 M glycerol in the culture medium. However, the polyols erythritol and sorbitol caused a small but significant loss of cells from the heat-resistant G1 compartment. The cell cycle redistribution with prolonged incubation (6 hr) in polyol-supplemented medium is expected to increase the heat sensitivity of the perturbed cell population; the observed heat protection by polyols suggests that heat resistance in the presence of polyols is not an artifact of an asynchronous cell system. Instead, the data identify a family of heat-protective compounds that may occur naturally in mammalian cells.