Visual Acuity and Retinal Thickness and Sensitivity after Intravitreal Ranibizumab Injection for Macular Edema in Branch Retinal Vein Occlusion.

Background/Objectives: To investigate changes in visual acuity and retinal sensitivity and thickness after intravitreal ranibizumab injection (IRI) for macular edema in branch retinal vein occlusion (BRVO) patients. Methods: This study evaluated 34 patients with treatment-naïve BRVO and at least 6 months' follow-up after pro re nata IRI. Best-corrected visual acuity (BCVA) was determined as the logarithm of the minimum angle of resolution (logMAR). In nine retinal regions, retinal sensitivity was calculated by MP-3 microperimetry; and in nine macular subfields, retinal thickness was measured by optical coherence tomography (OCT); evaluations were performed before IRI and then monthly for 6 months. Results: IRI significantly improved visual acuity and retinal sensitivity and thickness. In patients with good improvement in BCVA (change in logMAR > 0.2), IRI significantly improved retinal sensitivity in eight of nine regions, i.e., in all except the outer non-occluded region, and in patients with poor improvement in BCVA (change in logMAR < 0.2), in six of nine regions, i.e., not in the inner, outer non-occluded, and outer temporal regions. We found significant differences in the trend profile in the foveal, outer occluded, and inner nasal regions between patients with good and poor improvement in BCVA. Conclusions: The findings suggest that IRI improves visual acuity and retinal sensitivity and thickness and that retinal effects may vary between patients with good and poor visual improvement.

Uptake of Fluorescein via a pH-Dependent Monocarboxylate Transporter by Human Kidney 2 (HK-2) Cells.

Herein, we investigated whether a fluorescent probe for an organic anion transporter (OAT), fluorescein (FLS), could be accumulated by human kidney 2 (HK-2) cells derived from human kidney proximal tubular epithelia. HK-2 cells took up FLS in a pH-dependent and concentration-dependent manner. FLS accumulation by HK-2 cells was inhibited by monocarboxylic acids, ibuprofen, rosuvastatin, and indoleacetic acid but not by typical substrates for OATs. A typical protonophore, carbonyl cyanide p-trichloromethoxyphenylhydrazone completely abolished FLS accumulation by HK-2 cells. The FLS efflux process from the preloaded HK-2 cells exhibited substantial trans-stimulation by the excess amount of extracellular FLS transport inhibitable monocarboxylate compounds such as 2,4-dichloro phenoxyacetic acid, fluvastatin, ibuprofen, indoleacetic acid, salicylic acid and rosuvastatin, indicating that the FLS transporter can recognize and accumulate them into the cells in a pH-dependent manner. The involvement of the FLS transporter in the reabsorption of monocarboxylic compounds was indicated by demonstrating that the pH-dependent FLS uptake is inhibited by various monocarboxylates in rabbit renal brush border membrane vesicles. pH-dependent FLS uptake was trans-stimulated by the inhibitable monocarboxylates. Collectively, the present data indicate that the pH-dependent transporters expressed in HK-2 cells are involved in the reabsorption of monocarboxylates from the urinary fluid into the tubular epithelia.

Dual action of serotonin on local excitatory and inhibitory neural circuits regulating the corticotropin-releasing factor neurons in the paraventricular nucleus of the hypothalamus.

Serotonergic neurons originating from the raphe nuclei have been proposed to regulate corticotropin-releasing factor (CRF) neurons in the paraventricular nucleus of the hypothalamus (PVH). Since glutamate- and γ-aminobutyric acid (GABA)-containing neurons, constituting the hypothalamic local circuits, innervate PVH CRF neurons, we examined whether they mediate the actions of serotonin (5-hydroxytryptamine [5-HT]) on CRF neurons. Spontaneous excitatory postsynaptic currents (sEPSCs) or spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded in PVH CRF neurons, under whole cell patch-clamp, using the CRF-modified yellow fluorescent protein (Venus) ΔNeo mouse. Serotonin elicited an increase in the frequency of sEPSCs in 77% of the cells and a decrease in the frequency of sIPSCs in 71% of the cells, tested in normal medium. Neither the amplitude nor decay time of sEPSC and sIPSC was affected, thus the site(s) of action of serotonin may be presynaptic. In the presence of tetrodotoxin (TTX), serotonin had no significant effects on either parameter of sEPSC or sIPSC, indicating that the effects of serotonin are action potential-dependent, and that the presynaptic interneurons are largely intact within the slice; distant neurons may exist, though, since some 20%-30% of neurons did not respond to serotonin without TTX. We next examined through what receptor subtype(s) serotonin exerts its effects on presynaptic interneurons. DOI (5-HT2A/2C agonist) mimicked the action of serotonin on the sIPSCs, and the serotonin-induced decrease in sIPSC frequency was inhibited by a selective 5-HT2C antagonist RS102221. 8-OH-DPAT (5-HT1A/7 agonist) mimicked the action of serotonin on the sEPSCs, and the serotonin-induced increase in sEPSC frequency was inhibited by a selective 5-HT7 antagonist SB269970. Thus, serotonin showed a dual action on PVH CRF neurons, by upregulating glutamatergic- and downregulating GABAergic interneurons; the former may partly be mediated by 5-HT7 receptors, whereas the latter by 5-HT2C receptors. The CRF-Venus ΔNeo mouse was useful for the electrophysiological examination.

Anti-Vascular Endothelial Growth Factor Therapy with or Without Initial Steroid Therapy for Macular Edema in Branch Retinal Vein Occlusion.

Purpose: In branch retinal vein occlusion (BRVO), administering steroid injections to inhibit expression of inflammatory factors in the first phase of macular edema may reduce recurrence of the edema. The purpose of our study was to investigate the functional and morphological prognosis and frequency of recurrence after injection of an anti-vascular endothelial growth factor (VEGF) with and without initial steroid therapy to treat macular edema with BRVO. Patients and Methods: Patients with BRVO and macular edema (41 eyes) received intravitreal ranibizumab injection (IRI) alone (IRI group, 21 eyes) or subtenon triamcinolone (STTA) injection and IRI (combination group, 20 eyes). Patients in both groups with recurrent macular edema received further IRI as appropriate. A laser flare meter was used to assess aqueous flare values, and an optical coherence tomography device was used to measure central macular thickness (CMT). Before the first treatment, we obtained samples of aqueous humor and analyzed them by the suspension array method to evaluate VEGF, placental growth factor (PlGF), platelet-derived growth factor (PDGF)-AA, soluble intercellular adhesion molecule (sICAM)-1, monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-6, IL-8, and interferon-inducible 10-kDa protein (IP-10). Results: The two groups were not significantly different with regard to levels of VEGF, PlGF, PDGF-AA, sICAM-1, MCP-1, IL-6, IL-8, or IP-10. Best-corrected visual acuity, CMT, and aqueous flare value (IRI group, baseline 8.69 ± 4.55 photon counts/ms; combination group, baseline 9.21 ± 3.72 photon counts/ms) improved significantly in both groups without significant intergroup differences. Analyses showed no significant intergroup differences in the mean number of IRIs during the 12-month follow-up, but the proportion of patients without recurrence (ie, who received only one IRI) was significantly higher in the combination group than in the IRI group (P = 0.032). Furthermore, the time to initial recurrence was significantly longer in the combination group than in the IRI group (P = 0.003). Conclusion: These findings suggest that initial STTA injection and IRI may have a synergistic effect in patients with BRVO and macular edema in that they increase the time between anti-VEGF treatments.

Effects of Intravitreal Ranibizumab Injection on Peripheral Retinal Microcirculation and Cytokines in Branch Retinal Vein Occlusion with Macular Edema.

Background and Objectives: To investigate peripheral blood flow in retinal vessels and vessel diameters after intravitreal ranibizumab injection (IRI) and the relationship between these parameters and cytokines in branch retinal vein occlusion (BRVO) with macular edema. Materials and Methods: We assessed relative flow volume (RFV) and the width of the main and branch retinal arteries and veins in the occluded and non-occluded regions before and after IRI in 37 patients with BRVO and macular edema. Measurements were made using laser speckle flowgraphy (LSFG). When performing IRI, we obtained samples of aqueous humor and analyzed them using the suspension array method to evaluate vascular endothelial growth factor (VEGF), placental growth factor (PlGF), platelet-derived growth factor (PDGF)-AA, soluble intercellular adhesion molecule (sICAM)-1, monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-6, IL-8, and interferon-inducible 10-kDa protein (IP-10). Results: In both retinal regions, before and after IRI, the RFV in the main artery and vein showed a significant correlation with the summed RFV in the respective branch vessels 1 and 2. In the occluded region, the RFV in the main vein was significantly negatively correlated with MCP-1, PDGF-AA, IL-6, and IL-8; the RFV in branch vein 1 was significantly negatively correlated with PlGF, MCP-1, IL-6, and IL-8; PDGF-AA was significantly negatively correlated with the width of the main and branch veins; and the RFVs of the main artery and vein decreased significantly from before to 1 month after IRI. Conclusions: Contrary to expectations, the study found that anti-VEGF therapy does not affect RFV in arteries and veins in patients with BRVO and macular edema. Furthermore, retinal blood flow is poor in patients with high MCP-1, IL-6, and IL-8. Finally, high PDGF-AA may result in smaller venous diameters and reduced retinal blood flow.

Elucidation of a Thermodynamical Feature Attributed to Substrate Binding to the Prokaryotic H+/Oligopeptide Cotransporter YdgR with Calorimetric Analysis: The Substrate Binding Driven by the Change in Entropy Implies the Release of Bound Water Molecules from the Binding Pocket.

Here, we have elucidated the substrate recognition mechanism by a prokaryotic H+/oligopeptide cotransporter, YdgR, using isothermal titration calorimetry. Under acidic conditions (pH 6.0), the binding of a dipeptide, Val-Ala, to YdgR elicited endothermic enthalpy, which compensated for the increase in entropy due to dipeptide binding. A series of dipeptides were used in the binding titration. The dipeptides represent Val-X and X-Val, where X is Ala, Ser, Val, Tyr, or Phe. Most dipeptides revealed endothermic enthalpy, which was completely compensated by the increase in entropy due to dipeptide binding. The change in enthalpy due to binding correlated well with the change in entropy, whereas the Gibbs free energy involved in the binding of the dipeptide to YdgR remained unchanged irrespective of dipeptide sequences, implying that the binding reaction was driven by entropy, that is, the release of bound water molecules in the binding pocket. It is also important to clarify that, based on the prediction of water molecules in the ligand-binding pocket of YdgR, the release of three bound water molecules in the putative substrate binding pocket occurred through binding to YdgR. In the comparison of Val-X and X-Val dipeptides, the N-terminal region of the binding pocket might contain more bound water molecules than the C-terminal region. In light of these findings, we suggest that bound water molecules might play an important role in substrate recognition and binding by YdgR.

Role of Novel Inflammatory Factors in Central Retinal Vein Occlusion with Macular Edema.

Background and Objectives: To investigate associations among the aqueous humor levels of novel inflammatory factors, including FMS-related tyrosine kinase 3 ligand (Flt-3L), fractalkine, CXC chemokine ligand 16 (CXCL-16), and endocan-1; the severity of macular edema in central retinal vein occlusion (CRVO); and the prognosis of CRVO with macular edema after antivascular endothelial growth factor (VEGF) therapy. Materials and Methods: Aqueous humor was obtained during anti-VEGF treatment with intravitreal ranibizumab injection (IRI) in patients with CRVO and macular edema (n = 19) and during cataract surgery in patients with cataracts (controls, n = 20), and the levels of VEGF and novel inflammatory factors were measured. Macular edema was evaluated by central macular thickness (CMT) and neurosensory retinal thickness (TNeuro), and improvement was evaluated by calculating the percentage change in CMT and TNeuro from before to 1 month after IRI. Results: The levels of VEGF and the novel inflammatory factors were significantly higher in the CRVO group, and the levels of Flt-3L, CXCL-16, and endocan-1 were significantly correlated with each other and with the aqueous flare value. Baseline levels of Flt-3L, CXCL-16, and endocan-1 had a significantly negative correlation with the change in CMT, and the baseline level of CXCL-16 was significantly negatively correlated with the change in TNeuro. Conclusions: Relations among novel inflammatory factors should be further investigated. These findings may help improve understanding of macular edema in CRVO patients and aid the development of new treatments targeting novel inflammatory factors.

Protonation State of a Histidine Residue in Human Oligopeptide Transporter 1 (hPEPT1) Regulates hPEPT1-Mediated Efflux Activity.

To clarify the role of an amino acid residue in the pH-dependent efflux process in Chinese hamster ovary (CHO) cells expressing the human oligopeptide transporter hPEPT1 (CHO/hPEPT1), we determined the effect of extracellular pH on the hPEPT1-mediated efflux process. The efflux of glycylsarcosine (Gly-Sar), a typical substrate for hPEPT1, was determined using an infinite dilution method after cells were preloaded with [3H]-Gly-Sar. The efflux of [3H]-Gly-Sar was stimulated by 5 mM unlabeled hPEPT1 substrates in the medium. This trans-stimulation phenomenon showed that hPEPT1 mediated the efflux of [3H]-Gly-Sar from CHO/hPEPT1 and that hPEPT1 is a bi-directional transporter. We then determined the effect of extracellular pH (varying from 8.0 to 3.5) on the efflux activity. The efflux activity by hPEPT1 decreased with the decrease in extracellular pH. The Henderson-Hasselbälch-type equation, which fitted well to the pH-profile of efflux activity, indicated that a single amino acid residue with a pKa value of approximately 5.7 regulates the efflux activity. The pH-profile of the efflux activity remained almost unchanged irrespective of the proton gradient across the plasma membrane. In addition, the chemical modification of the histidine residue with diethylpyrocarbonate completely abolished the efflux activity from cells, which could be prevented by the presence of 10 mM Gly-Sar. These data indicate that the efflux process of hPEPT1 is also regulated in a pH-dependent manner by the protonation state of a histidine residue located at or near the substrate recognition site facing the extracellular space.

Machine-learning prediction of self-care activity by grip strengths of both hands in poststroke hemiplegia.

To investigate the relationships between grip strengths and self-care activities in stroke patients using a non-linear support vector machine (SVM).Overall, 177 inpatients with poststroke hemiparesis were enrolled. Their grip strengths were measured using the Jamar dynamometer on the first day of rehabilitation training. Self-care activities were assessed by therapists using Functional Independence Measure (FIM), including items for eating, grooming, dressing the upper body, dressing the lower body, and bathing at the time of discharge. When each FIM item score was ≥6 points, the subject was considered independent. One thousand bootstrap grip strength datasets for each independence and dependence in self-care activities were generated from the actual grip strength. Thereafter, we randomly assigned the total bootstrap datasets to 90% training and 10% testing datasets and inputted the bootstrap training data into a non-linear SVM. After training, we used the SVM algorithm to predict a testing dataset for cross-validation. This validation procedure was repeated 10 times.The SVM with grip strengths more accurately predicted independence or dependence in self-care activities than the chance level (mean ±â€Šstandard deviation of accuracy rate: eating, 0.71 ±â€Š0.04, P < .0001; grooming, 0.77 ±â€Š0.03, P < .0001; upper-body dressing, 0.75 ±â€Š0.03, P < .0001; lower-body dressing, 0.72 ±â€Š0.05, P < .0001; bathing, 0.68 ±â€Š0.03, P < .0001).Non-linear SVM based on grip strengths can prospectively predict self-care activities.

[Relevance of the five-repetition sit-to-stand test for diagnosing sarcopenia in elderly inpatients with cardiac disease].

PURPOSE: The aim of this study was to determine the reference values for diagnosing sarcopenia using the five-repetition sit-to-stand test in elderly inpatients with cardiac disease. METHODS: We studied 71 inpatients with cardiac disease ≥65 years of age (mean age 78.0±7.9 years, 42.3% women) who were admitted between April 2015 and March 2016. Patients were assessed for sarcopenia, and we performed the five-repetition sit-to-stand test. We defined sarcopenia using the Asian Working Group for Sarcopenia-suggested diagnostic algorithm. A logistic regression analysis was performed to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of the relationship between sarcopenia and the five-repetition sit-to-stand test. A multivariate analysis showed that the age, admission diagnosis, the New York Heart Association classification, the Charlson comorbidity index, and the ratio of extracellular to total body water were relevant covariates. The cut-off value of the five-repetition sit-to-stand test to diagnose sarcopenia was determined using a receiver operating characteristic curve. RESULTS: Sarcopenia was diagnosed in 25 patients (35.2%). A multivariate logistic regression analysis showed that the five-repetition sit-to-stand test was significantly associated with sarcopenia (p=0.024), and the OR (95% CI) was 1.31 (1.04-1.65). The cut-off value of the five-repetition sit-to-stand test to diagnose sarcopenia was 10.9 s (sensitivity 80.0%, specificity 70.0%, area under the curve 0.83). CONCLUSIONS: The five-repetition sit-to-stand test is a useful screening tool for sarcopenia in elderly inpatients with cardiac disease. The cut-off value to diagnose sarcopenia was 10.9 s in this study.

Transport of 2,4-dichloro phenoxyacetic acid by human Na+-coupled monocarboxylate transporter 1 (hSMCT1, SLC5A8).

Using X. laevis oocyte expression system, we investigated whether human Na+-coupled monocarboxylate transporter 1 (SLC5A8, hSMCT1) is involved in 2,4-dichlorophenoxyacetate (2,4-D) uptake by the renal tubular epithelial cells. 2,4-D is a herbicide that causes nephrotoxicity. Heterologous expression of hSMCT1 in X. laevis oocytes conferred the ability to take up 2,4-D; the induced uptake process was Na+-dependent and electrogenic. The Na+-dependent uptake of 2,4-D was inhibited not only by known hSMCT1 substrates, but also by many structural analogs of 2,4-D. The currents induced by 2,4-D, 4-chlorophenoxyacetate (4-CPA) and 2-methyl-4-chlorophenoxyacetate (MCPA) were saturable: the rank order of the maximal induced current and the affinity for hSMCT1was 2,4-D > 4-CPA > MCPA. The relationship between the structures of the derivatives and their transport activity implied specific structural features in a compound for recognition as a substrate by hSMCT1. Furthermore, we have demonstrated using purified rabbit renal brush-border membrane vesicles that 2,4-D potently inhibited the Na+-dependent uptake of pyroglutamate, a typical substrate for Smct1, and that 2,4-D uptake process was Na+-dependent, saturable and inhibitable by a potent blocker, ibuprofen. We conclude that hSMCT1 is involved partially in the renal reabsorption of 2,4-D and its derivatives and their nephrotoxicity.

[The isometric knee extension strength threshold for maintaining walking speed and step length in older male inpatients].

AIM: To clarify the minimum knee extension muscle strength needed to maintain walking speed and step length in older male inpatients. METHOD: The participants were 786 male inpatients of ≥65 years of age without cerebrovascular disorder, orthopedic disease, malignancy, or dementia. We investigated the participants' isometric knee extension muscle force (kgf/kg), maximum walking speed (m/s) and step length, based on their medical records. The relationship of walking speed and step length to isometric knee extension muscle force was fitted to linear and nonlinear models, and the respective R2 values were compared. Next, the muscle force data were divided into two groups, and two linear functions were calculated. Then, the muscle force value that minimized the sum of the residual sum of squares of the two linear function expressions was obtained. RESULTS: The R2 values of each equation in the nonlinear model were higher than those in the linear model. Among all participants, the muscle force values that minimized the sum of the residual sum of squares for walking speed and step length were 0.33 kgf/kg and 0.43 kgf/kg, respectively. Among participants of ≤74 years of age, the muscle force value that minimized the sum of the residual sum of squares was 0.30 kgf/kg for both walking speed and step length, whereas the values were 0.32 kgf/kg and 0.43 kgf/kg, respectively, in participants of ≥75 years of age. CONCLUSION: Walking speed and step length were significantly decreased in male inpatients of 65-74 years of age when the isometric knee extension force values for both were <0.30 kgf/kg. In contrast, among male inpatients of ≥75 years of age, these values were significantly decreased when the respective isometric knee extension muscle force values were <0.32 kgf/kg and <0.43 kgf/kg.

Impairment in toileting behavior after a stroke.

AIM: Dependence for toileting is the most problematic aspect for patients after a stroke. However, the relative difficulty of each component of toileting and the predictors for independent performance of these activities are unknown. We investigated these issues in stroke patients using Boltzmann sigmoid and generalized linear modeling. METHODS: We carried out a cross-sectional correlation study, including 107 adult inpatients, hospitalized for a stroke. We assessed the activity components of toileting, as well as evaluated physical impairment using the Fugl-Meyer Assessment, impairments in balance using the Berg Balance Scale, cognitive impairments using the Mini-Mental State Examination and the presence or absence of unilateral spatial neglect or aphasia. RESULTS: Boltzmann sigmoid modeling showed that the total scores required to obtain a response at 50% of the maximal value for the required components of toileting ranged between 2.691 and 34.962 points, for the components of "wearing pants" and "cutting the toilet paper," respectively. A generalized linear model showed that the Berg Balance Scale score was a significant predictor for independent performance on most component activities of toileting. CONCLUSIONS: The component of toileting that was easiest to carry out was cutting the toilet paper, and the most difficult was wearing pants. Balance impairment was an independent predictor of independent toileting after stroke. This detailed toileting assessment enabled us to document the most difficult components of toileting, and to assess the motor and process skills required for independent toileting. Geriatr Gerontol Int 2018; 18: 1166-1172.

The Phenomenon of Albumin-Mediated Hepatic Uptake of Organic Anion Transport Polypeptide Substrates: Prediction of the In Vivo Uptake Clearance from the In Vitro Uptake by Isolated Hepatocytes Using a Facilitated-Dissociation Model.

The effects of bovine serum albumin and human serum albumin on the unbound hepatic uptake clearance (PSu,inf) of the organic anion-transporting polypeptide substrates 1-anilino-8-naphthalene sulfonate (ANS) and pitavastatin (PTV) were determined using primary cultured rat hepatocytes and isolated human hepatocytes, respectively. The PSu,inf value of hepatocytes was estimated by dividing the initial uptake rate of these anions by their unbound concentrations. The PSu,inf values for ANS and PTV were enhanced in the presence of albumin, thereby demonstrating the phenomenon of "albumin-mediated" hepatic uptake. We previously constructed a "facilitated-dissociation" model, in which the interaction of the ligand-albumin complex with the cell surface enhanced the dissociation of that complex to provide unbound ligand for uptake to the hepatocytes [J Pharmacokinet Biopharm 16:165-181 (1988)]. That model was able to describe accurately the relationship between the enhancement of the PSu,inf values and the albumin concentration. By considering the enhancement of hepatic uptake clearance by albumin using this facilitated-dissociation model, we could predict accurately the PSu,inf in vivo from that obtained in isolated hepatocytes. In the light of these findings, we suggest that the facilitated-dissociation model is applicable to describing the phenomenon of albumin-mediated hepatic uptake via organic anion transporters and to evaluating hepatic uptake clearance in vivo.

Involvement of monocarboxylate transporter 1 (SLC16A1) in the uptake of l-lactate in human astrocytes.

PURPOSE: Astrocytes, the most abundant glial cells in the central nervous system (CNS), help neurons survive. Monocarboxylate transporters (MCTs) are reported to transport l-lactate, which is important for CNS physiology and cognitive function. However, it remains unclear which MCT isoform is functionally expressed by human astrocytes. The aim of this study was to establish the contribution of each MCT isoform to l-lactate transport in human astrocytes. METHODS: The function of l-lactate transport was studied using NHA cells as a human astrocyte model and radiolabeled l-lactate. The expression of MCT in human astrocytes was detected by immunohistochemistry staining. RESULTS: The cellular uptake of l-lactate was found to be pH- and concentration-dependent with a Km value for l-lactate uptake of 0.64mM. This Km was similar to what has been previously established for MCT1-mediated l-lactate uptake. α-Cyano-4- hydroxycinnamate (CHC) and 5-oxoproline, which are both MCT1 inhibitors, were found to significantly inhibit the uptake of l-lactate, suggesting MCT1 is primarily responsible for l-lactate transport. Moreover, MCT1 protein was expressed in human astrocytes. CONCLUSION: pH-dependent l-lactate transport is mediated by MCT1 in human astrocytes.

The flexible cytoplasmic loop 3 contributes to the substrate affinity of human monocarboxylate transporters.

Human monocarboxylate transporters (hMCTs/SLC16As) mediate the transport of small molecular weight monocarboxylates. Among hMCTs, hMCT1 exhibits high-affinity l-lactate transport and broad substrate recognition, whereas hMCT4 shows highly specific substrate recognition and low-affinity l-lactate transport, indicating that hMCT1 and hMCT4 have different roles in the body. However, the molecular mechanism of transporter-mediated substrate transport remains unknown. The aim of this study is to identify the domain, which determines the substrate selectivity and affinity of hMCT1 and hMCT4. We constructed a chimera, hMCT4/1, in which the cytoplasmic loop 3 (TM6/7loop) region of hMCT4 was replaced by the corresponding region of hMCT1. Xenopus laevis oocyte heterologous expression system was used to characterize functional features of the chimera. We have demonstrated that the substrate affinity of hMCT1 and hMCT4 depends on the TM6/7loop. Non-conserved His237 residue in the TM6/7loop functions as a regulatory moiety of the substrate affinity. In contrast, the substrate selectivity of the transporters did not depend on the TM6/7loop, suggesting that the domain is not directly involved in substrate recognition. Our study provides important insights into the structures and functions of hMCT1 and hMCT4 transporters. These findings contribute to the development of novel hMCT1 and/or hMCT4 inhibitors as anticancer agents.

Interaction of atorvastatin with the human glial transporter SLC16A1.

Solute carrier (SLC) 16A1 is a pH-dependent carrier of 5-oxoproline, a derivative of the amino acid. SLC16A1 interacts with carboxylate group-containing substrates, which are also present in atorvastatin, and might be the reason for its ability to interact with atorvastatin. Does atorvastatin interact with the carrier? Does it also interact with the carrier via the substrate recognition site? This study was carried out to answer these questions. Polymerase chain reaction was used to determine the expression of SLC16A1 in normal human astrocytes. We induced SLC16A1 expression in a mammalian cell line and in Xenopus laevis oocytes. We used [(3)H] 5-oxoproline for direct measurement of SLC16A1-specific transport activity. SLC16A1 was clearly observed in normal human astrocytes. 3-Hydroxy-3-methyl-glutaryl-CoA reductase inhibitors inhibited the SLC16A1-specific transport of 5-oxoproline. Atorvastatin was the most potent inhibitor, with an inhibition constant of 40µM. The drug was a non-competitive inhibitor of SLC16A1. In the present study, we showed non-competitive inhibition of SLC16A1-specific transport activity by atorvastatin. However, the affinity between the drug and the carrier was extremely low. Therefore, the interaction of atorvastatin with SLC16A1 is unlikely to be a problem in clinical practice.

Effect of diclofenac on SLC16A3/MCT4 by the Caco-2 cell line.

In the present study, we demonstrated that monocarboxylate transporter 4 (MCT4) is functionally expressed in Caco-2 cells. We studied the effects of 4 nonsteroidal anti-inflammatory drugs on the uptake of l-lactate as a good substrate of MCT4 by the cells. The monocarboxylate drugs inhibited the uptake of l-lactate into the cells. Diclofenac, as a member of the aryl-acetic acid group of nonsteroidal anti-inflammatory drugs, was the most potent inhibitor, with an inhibition constant of 20 µM. In the next study, we determined the type of inhibition for diclofenac. An l-lactate carrier is non-competitively inhibitable by the drug. We also demonstrated, in Xenopus oocyte expression system, potential of diclofenac for MCT4 inhibitor. The present results could provide a useful tool to discover MCT4-specific inhibitors.

Involvement of Monocarboxylate Transporter 4 Expression in Statin-Induced Cytotoxicity.

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are the most widely used cholesterol-lowering agents for prevention of obstructive cardiovascular events. However, statins can cause a variety of skeletal muscle problems, and exercise leads to an increase in statin-induced muscle injury. Exercise induces the protein content of monocarboxylate transporter 4 (MCT4), which is expressed strongly in skeletal muscle and is thought to play a major role in the transport of metabolically important monocarboxylates such as l-lactate. We previously reported that α-cyano-4-hydroxycinnamate, an MCT4 inhibitor, increased the inhibition of growth of RD cells, a prototypic embryonal rhabdomyosarcoma cell line (an RD cell line), as a model of in vitro skeletal muscle, induced by a statin. However, it is unclear whether statin-induced RD cell cytotoxicity is associated with MCT4 expression. We, therefore, examined the relationship between statin-induced cytotoxicity and MCT4 expression in RD cells. Atorvastatin reduced the number of viable cells and upregulated MCT4, but not MCT1, mRNA level in a concentration-dependent manner. MCT4 knockdown suppressed atorvastatin-, simvastatin-, and fluvastatin-induced reduction of cell viability and apoptosis compared with negative control-treated cells. In this study, we demonstrated that MCT4 expression is associated with statin-induced cytotoxicity.

Influence of high glucose state on bromopyruvate-induced cytotoxity by human colon cancer cell lines.

BACKGROUND: Attention must be paid to chemotherapy for cancer patients in a hyperglycemia state. It is difficult for chemotherapy to cure cancer in patients in a hyperglycemia state. This study was carried out to determine the change in cell viability after treatment with bromopyruvate, which is an alkylating drug with anti-tumor activity, in a high glucose condition. METHODS: The function of l-lactate and bromopyruvate transport was studied using human colon cancer cell lines (LoVo and HT-29) and radiolabeled l-lactate and bromopyruvate. Cell viability was monitored by the trypan blue exclusion assay. The expression level of human monocarboxylate transporter 1 (hMCT1) was evaluated by Western blot analysis. RESULTS: Bromopyruvate-induced cell death was suppressed by a high glucose condition. l-Lactate and bromopyruvate uptake were suppressed by a high glucose condition. hMCT1 as a bromopyruvate carrier was functionally expressed in the cells. However, the expression of hMCT1 was suppressed by a high glucose state. CONCLUSIONS: Down-regulation of hMCT1 by a high glucose state is one of the possibilities of the bromopyruvate resistance. We should pay scrupulous attention to cancer chemotherapy for patients who have developed diabetes.