Involvement of sodium-glucose cotransporter-1 activities in maintaining oscillatory Cl- currents from mouse submandibular acinar cells.

In salivary acinar cells, cholinergic stimulation induces elevations of cytosolic [Ca2+]i to activate the apical exit of Cl- through TMEM16A Cl- channels, which acts as a driving force for fluid secretion. To sustain the Cl- secretion, [Cl-]i must be maintained to levels that are greater than the electrochemical equilibrium mainly by Na+-K+-2Cl- cotransporter-mediated Cl- entry in basolateral membrane. Glucose transporters carry glucose into the cytoplasm, enabling the cells to produce ATP to maintain Cl- and fluid secretion. Sodium-glucose cotransporter-1 is a glucose transporter highly expressed in acinar cells. The salivary flow is suppressed by the sodium-glucose cotransporter-1 inhibitor phlorizin. However, it remains elusive how sodium-glucose cotransporter-1 contributes to maintaining salivary fluid secretion. To examine if sodium-glucose cotransporter-1 activity is required for sustaining Cl- secretion to drive fluid secretion, we analyzed the Cl- currents activated by the cholinergic agonist, carbachol, in submandibular acinar cells while comparing the effect of phlorizin on the currents between the whole-cell patch and the gramicidin-perforated patch configurations. Phlorizin suppressed carbachol-induced oscillatory Cl- currents by reducing the Cl- efflux dependent on the Na+-K+-2Cl- cotransporter-mediated Cl- entry in addition to affecting TMEM16A activity. Our results suggest that the sodium-glucose cotransporter-1 activity is necessary for maintaining the oscillatory Cl- secretion supported by the Na+-K+-2Cl- cotransporter activity in real time to drive fluid secretion. The concerted effort of sodium-glucose cotransporter-1, Na+-K+-2Cl- cotransporter, and apically located Cl- channels might underlie the efficient driving of Cl- secretion in different secretory epithelia from a variety of animal species.

Taste-taste associations in chemotherapy-induced subjective taste alterations: findings from a questionnaire survey in an outpatient clinic.

PURPOSE: Chemotherapy-induced taste alteration is a side effect that can result in malnutrition and reduced quality of life in cancer patients. However, the underlying causes of this phenomenon remain unclear, and evidence-based treatments have not been established. This study focused on patients' subjective symptoms of taste alterations aimed to explore how the sensitivity to basic tastes changes due to anticancer agents and how alterations in one taste perception are associated with changes in other tastes during chemotherapy. METHODS: A cross-sectional questionnaire-based interview survey was conducted on 215 patients undergoing chemotherapy. The subjective sensitivity to each basic taste was assessed using a visual analog scale, and the incidence of taste alterations due to different chemotherapy regimens was calculated. Multivariate logistic regression analysis was performed to determine whether there were associations between changes in one taste sensitivity and changes in other taste sensitivities. RESULTS: Approximately half (49.5%) of the patients experienced chemotherapy-induced taste alterations. An analysis of subjective changes in basic tastes revealed that the salt and umami taste systems were more sensitive to chemotherapy than other taste systems. Patients with altered sensitivity to sweet taste were significantly more likely to report altered sensitivity to salt, bitter, and sour tastes. Moreover, umami-salt and bitter-sour taste sensitivities were significantly related to each other. CONCLUSION: This study suggests that changes in subjective sensitivities to one basic taste during chemotherapy may be accompanied by changes in other tastes in specific combinations. Considering taste associations in dietary guidance may help improve the nutritional status of cancer patients experiencing taste alterations due to chemotherapy.

Resting saliva volume as a risk factor for hypogeusia: A retrospective study.

OBJECTIVES: The causes of hypogeusia include zinc deficiency, systemic illness, and consumption of drugs. Notably, patients with oral cavity diseases such as oral candidiasis and salivary gland hypofunction may present with risk factors that remain unreported. Hence, this study aimed to investigate the relationship between age, sex, smoking status, serum zinc concentration, oral candidiasis, saliva volume, and taste function in patients with hypogeusia. SUBJECTS AND METHODS: Overall, 335 participants who complained of taste abnormalities underwent a taste test. Based on the recognition threshold value, the participants were classified as normal individuals (recognition threshold of 1 and 2) and patients with hypogeusia (recognition threshold of ≥3). The clinical characteristics, including resting saliva volume (RSV) and stimulated saliva volume (SSV), were compared, and a multivariate logistic regression analysis focusing on RSV was performed. RESULTS: Patients with hypogeusia had a lower RSV than normal individuals for all tastes, but not for SSV. Based on the results of regression analysis, RSV was identified as an independent predictor of hypogeusia for salty and bitter tastes. Moreover, the proportion of patients with decreased RSV increased as the number of taste qualities exceeding the reference recognition threshold increased. Furthermore, a decrease in RSV was associated with an increase in the recognition threshold for salty and bitter tastes. CONCLUSIONS: Based on the results of the present study, moisturizing the oral cavity may be useful against hypogeusia.

Effect of irinotecan administration on amiloride-sensitive sodium taste responses in mice.

Taste alteration is a frequently reported side effect in patients receiving the chemotherapeutic agent, irinotecan. However, the way in which irinotecan causes taste disturbance and the type of taste impairment that is affected remain elusive. Here, we used the two-bottle preference test to characterize behavioral taste responses and employed immunohistochemical analyses to clarify the types and mechanisms of taste alteration induced, in mice, by irinotecan administration. Irinotecan administration resulted in a reduced intake of sodium taste solution but had no effect on sweet taste responses, as determined in the two-bottle preference test. In the presence of amiloride, which inhibits the function of the epithelial sodium channel (ENaC) in the periphery, the intake of sodium taste solution was comparable between the irinotecan-treated and control groups. Immunohistochemical analyses revealed that α-ENaC immunoreactivity detected in taste bud cells decreased slowly after irinotecan administration, and that administration of irinotecan had little effect on the number of cells expressing the cellular proliferation marker, Ki67, within or around taste buds. Our results imply that irinotecan administration may be responsible for altered behavioral sodium taste responses originating from ENaC function in the periphery, while being accompanied by the reduction of α-ENaC expression at the apical membrane of taste receptor cells without disturbing taste cell renewal.

Characterization of the fatty acid profile in the ventral midbrain of mice exposed to dietary imbalance between omega-6 and omega-3 fatty acids during specific life stages.

OBJECTIVE: Omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are essential nutrients. Dietary imbalance between these PUFAs, in particular high in n-6 PUFAs and low in n-3 PUFAs (n-6high/n-3low), is common in modern society. We have previously reported that C57BL/6 mouse male offspring derived from mothers exposed to an n-6high/n-3low diet during the gestation had an augmented ventral midbrain dopamine system in adulthood; however, the fatty acid composition in this brain region has not yet been investigated. This follow-up study aims to characterize the fatty acid profile of the ventral midbrain of mice exposed to the n-6high/n-3low diet during specific life stages. RESULTS: n-6 PUFAs, especially linoleic acid, were increased in the ventral midbrain of offspring exposed to the n-6high/n-3low diet during the gestation compared to those exposed to a well-balanced control diet throughout life. On the other hand, n-3 PUFAs, especially docosahexaenoic acid, were decreased in the ventral midbrain of offspring exposed to the n-6high/n-3low diet during the gestation, lactation, or postweaning period compared to those exposed to the control diet throughout life. Thus, exposure to the n-6high/n-3low diet in pregnancy increases linoleic acid and that in any life stage decreases docosahexaenoic acid in the offspring's ventral midbrain.

The biphasic effect of extracellular glucose concentration on carbachol-induced fluid secretion from mouse submandibular glands.

Cholinergic agonists evoke elevations of the cytoplasmic free-calcium concentration ([Ca2+ ]i ) to stimulate fluid secretion in salivary glands. Salivary flow rates are significantly reduced in diabetic patients. However, it remains elusive how salivary secretion is impaired in diabetes. Here, we used an ex vivo submandibular gland perfusion technique to characterize the dependency of salivary flow rates on extracellular glucose concentration and activities of glucose transporters expressed in the glands. The cholinergic agonist carbachol (CCh) induced sustained fluid secretion, the rates of which were modulated by the extracellular glucose concentration in a biphasic manner. Both lowering the extracellular glucose concentration to less than 2.5 mM and elevating it to higher than 5 mM resulted in decreased CCh-induced fluid secretion. The CCh-induced salivary flow was suppressed by phlorizin, an inhibitor of the sodium-glucose cotransporter 1 (SGLT1) located basolaterally in submandibular acinar cells, which is altered at the protein expression level in diabetic animal models. Our data suggest that SGLT1-mediated glucose uptake in acinar cells is required to maintain the fluid secretion by sustaining Cl- secretion in real-time. High extracellular glucose levels may suppress the CCh-induced secretion of salivary fluid by altering the activities of ion channels and transporters downstream of [Ca2+ ]i signals.

Role of postsynaptic inositol 1, 4, 5-trisphosphate receptors in depotentiation in guinea pig hippocampal CA1 neurons.

The long-term potentiation (LTP) in the field excitatory postsynaptic potential (EPSP) induced at hippocampal CA1 pyramidal neuron synapses by delivery of high frequency stimulation (HFS), a tetanus of 100 pulses at 100Hz, is decreased (depotentiation) by a train of low frequency stimulation (LFS) of 1000 pulses at 2Hz applied 30min later. Inositol 1, 4, 5-trisphosphate receptors (IP3Rs) activated both during the HFS and after the LFS are involved in this depotentiation, the former triggering, and the latter modifying, LTP induction (decreasing the amplitude of the LTP established by the priming HFS). Furthermore, the decrease in the LTP at CA1 synapses requires activation of IP3Rs during LFS and activation of calcineurin after LFS. These results suggest that, at hippocampal CA1 neuron synapses, HFS-induced IP3R activation, which is modulated by the subsequent LFS, results in postsynaptic protein dephosphorylation after the LFS, leading to a decrease in the field EPSP and in the HFS-induced LTP.

Different rate-limiting activities of intracellular pH regulators for HCO3- secretion stimulated by forskolin and carbachol in rat parotid intralobular ducts.

Intracellular pH (pHi) regulation fundamentally participates in maintaining HCO3- release from HCO3--secreting epithelia. We used parotid intralobular ducts loaded with BCECF to investigate the contributions of a carbonic anhydrase (CA), anion channels and a Na+-H+ exchanger (NHE) to pHi regulation for HCO3- secretion by cAMP and Ca2+ signals. Resting pHi was dispersed between 7.4 and 7.9. Forskolin consistently decreased pHi showing the dominance of pHi-lowering activities, but carbachol gathered pHi around 7.6. CA inhibition suppressed the forskolin-induced decrease in pHi, while it allowed carbachol to consistently increase pHi by revealing that carbachol prominently activated NHE via Ca2+-calmodulin. Under NHE inhibition, forskolin and carbachol induced the remarkable decreases in pHi, which were slowed predominantly by CA inhibition and by CA or anion channel inhibition, respectively. Our results suggest that forskolin and carbachol primarily activate the pHi-lowering CA and pHi-raising NHE, respectively, to regulate pHi for HCO3- secretion.

TMEM16E (GDD1) exhibits protein instability and distinct characteristics in chloride channel/pore forming ability.

TMEM16E/GDD1 has been shown to be responsible for the bone-related late-onset disease gnathodiaphyseal dysplasia (GDD), with the dominant allele (TMEM16E(gdd) ) encoding a missense mutation at Cys356. Additionally, several recessive loss-of-function alleles of TMEM16E also cause late-onset limb girdle muscular dystrophy. In this study, we found that TMEM16E was rapidly degraded via the proteasome pathway, which was rescued by inhibition of the PI3K pathway and by the chemical chaperone, sodium butyrate. Moreover, TMEM16E(gdd) exhibited lower stability than TMEM16E, but showed similar propensity to be rescued. TMEM16E did not exhibit cell surface calcium-dependent chloride channel (CaCC) activity, which was originally identified in TMEM16A and TMEM16B, due to their intracellular vesicle distribution. A putative pore-forming domain of TMEM16E, which shared 39.8% similarity in 98 amino acids with TMEM16A, disrupted CaCC activity of TMEM16A via domain swapping. However, the Thr611Cys mutation in the swapped domain, which mimicked conserved cysteine residues between TMEM16A and TMEM16B, reconstituted CaCC activity. In addition, the GDD-causing cysteine mutation made in TMEM16A drastically altered CaCC activity. Based on these findings, TMEM16E possesses distinct function other than CaCC and another protein-stabilizing machinery toward the TMEM16E and TMEM16E(gdd) proteins should be considered for the on-set regulation of their phenotypes in tissues.

Predicting pharmacokinetic stability by multiple oral administration of atypical antipsychotics.

Lower fluctuation, i.e., lower peak-to-trough plasma-concentration variation at steady-state pharmacokinetics, has several advantages for the treatment of schizophrenia with antipsychotics. The reduction of peak concentration can decrease the risk of dose-dependent side effects, such as extrapyramidal symptom and somnolence, and by contrast the increase in trough concentration can decrease the incidence of lack of efficacy due to subtherapeutic drug concentration. Using a one-compartment simulation technique with pharmacokinetic parameters of each atypical antipsychotic collected from package inserts, the fluctuation index was calculated. Among the antipsychotics, the indices varied from 0.018 to 1.9, depending on dosing regimens, formulations and several pharmacokinetic properties. The order of simulated fluctuation index is active-moiety aripiprazole (b.i.d.)

Impairment of hippocampal long-term potentiation and failure of learning in mice treated with d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol.

Gangliosides (sialic acid-containing glycosphingolipids) play important roles in many physiological functions, including synaptic plasticity in the hippocampus, which has been suggested as the basal cellular process of learning and memory in the brain. In the present study, long-term potentiation (LTP) and long-term depression (LTD) in CA1 hippocampal neurons and learning behavior were examined in mice treated with (D)-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol ((D)-PDMP), an inhibitor of ganglioside biosynthesis. Mice treated with (D)-PDMP, but not those treated with (L)-PDMP, showed impairment of LTP induction in hippocampal CA1 neurons without any significant change in LTD formation and also showed a failure of learning in the 4-pellet taking test. These results indicate that de novo synthesis of gangliosides in the brain is involved in synaptic plasticity of LTP in mouse hippocampal CA1 neurons and plays important roles in learning and memory.

Suppressive effect of preconditioning low-frequency stimulation on subsequent induction of long-term potentiation by high frequency stimulation in hippocampal CA3 neurons.

We investigated the role of inositol 1, 4, 5-trisphosphate receptors (IP3Rs), activated during preconditioning low-frequency afferent stimulation (LFS), in the subsequent induction of long-term potentiation (LTP) in CA3 neurons in hippocampal slices from mature guinea pigs. Induction of LTP in the field excitatory postsynaptic potential (EPSP) by the delivery of high-frequency stimulation (HFS, a tetanus of two trains of 100 pulses at 100Hz with a 10s interval) to mossy fiber-CA3 neuron synapses was suppressed when CA3 synapses were preconditioned by the LFS of 1000 pulses at 2Hz and this effect was inhibited when the LFS preconditioning was performed in the presence of an IP3R antagonist or a protein phosphatase inhibitor. Furthermore, activation of group 1 metabotropic glutamate receptors (mGluRs) during HFS canceled the effects of an IP3R antagonist given during preconditioning LFS on the subsequent LTP induction at mossy fiber-CA3 synapses. These results suggest that, in hippocampal mossy fiber-CA3 neuron synapses, activation of IP3Rs during a preconditioning LFS results in dephosphorylation events that lead to failure of the HFS to induce subsequent LTP.

Solitary fibrous tumor of the pleura suddenly induced hypoglycemia before surgical treatment.

We present a case of a solitary fibrous tumor of the pleura with sudden onset, recurrent hypoglycemia. A 76-year-old smoking male with type-II diabetes mellitus admitted to our hospital for dyspnea and general malaise. Radiological findings revealed a large tumor occupying the right hemithorax. After bronchoscopic examination, the patient developed a fever and began to wheeze. Treatment with antibiotics and several other drugs improved his symptoms. Percutaneous needle biopsy confirmed the diagnosis. After these medical interventions, the patient suddenly developed recurrent hypoglycemia. After the right pneumonectomy, the patient never experienced hypoglycemia again. We should consider the possible relation between hypoglycemia and solitary fibrous tumor of the pleura, even when the patient is not hypoglycemic during the initial examination.

Membrane potential modulation of ionomycin-stimulated Ca(2+) entry via Ca (2+)/H (+) exchange and SOC in rat submandibular acinar cells.

Ionomycin (IM) at 5 microM mediates the Ca(2+)/H(+) exchange, while IM at 1 microM activates the store-operated Ca(2+) entry channels (SOCs). In this study, the effects of depolarization on both pathways were examined in rat submandibular acinar cells by increasing extracellular K(+) concentration ([K(+)](o)). IM (5 microM, the Ca(2+)/H(+) exchange) increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) to an extremely high value at 151 mM [K(+)](o). However, with increasing [K(+)](o), the rates of Ca(2+) entry decreased in a linear relationship. The reversal potential (E (rev)) for the Ca(2+)/H(+) exchange was +93 mV, suggesting that IM (5 microM) exchanges 1 Ca(2+) for 1 H(+). Thus, depolarization decreases the Ca(2+) influx via the Ca(2+)/H(+) exchange because of its electrogenicity (1 Ca(2+) for 1 H(+)). On the other hand, IM (1 microM, the SOCs) abolished an increase in [Ca(2+)](i) at 151 mM [K(+)](o). With increasing [K(+)](o), the rate of Ca(2+) entry immediately decreased linearly. The E (rev) for the SOC was +3.7 mV, suggesting that the SOCs are nonselective cation channels and less selective for Ca(2+) over Na(+) (P (Ca)/P (Na) = 8.2). Moreover, an increase in extracellular Ca(2+) concentration (20 mM) enhanced the Ca(2+) entry via the SOCs at 151 mM [K(+)](o), suggesting depolarization does not inhibit the SOCs and decreases the driving force for the Ca(2+) entry. This suggests that membrane potential changes induced by a secretory stimulation finely regulate the [Ca(2+)](i) via the SOCs in rat submandibular acinar cells. In conclusion, IM increases [Ca(2+)](i) via two pathways depending on its concentration, the exchange of 1 Ca(2+) for 1 H(+) at 5 muM and the SOCs at 1 microM.

Pharmacologic modulation of alveolar liquid clearance in transplanted lungs by phentolamine and FK506.

BACKGROUND: The lung's capacity to clear alveolar fluid can determine the severity of the edema seen after transplantation. We recently observed that alveolar liquid clearance was decreased in transplanted lungs. This study evaluates the ability of phentolamine and FK506 to modulate the severity of lung injury and the decline in alveolar liquid clearance after transplantation. METHODS: A canine orthotopic single-lung transplantation model was used. The lungs were preserved with a low-potassium-dextran solution (50 mL/kg) and transplanted after 3 hours of cold ischemia. The experimental protocol included a control group, a phentolamine group, in which donor lungs were infused with phentolamine (2 mg/kg), and a FK506 group, in which the animals received FK506 (25 mg/kg per hour) intravenously during reperfusion. After 4 hours of reperfusion, alveolar liquid clearance, wet-to-dry ratios, lung epithelial Na(+) channel expression, and the response to beta-adrenergic stimulation were measured. RESULTS: The increase in wet-to-dry ratios of transplanted lungs was less pronounced in the phentolamine and FK506 groups. The FK506 treatment led to improvement of alveolar liquid clearance. Neither phentolamine nor FK506 influenced lung epithelial Na(+) channel expression in transplanted lungs or preserved alveolar cell ability to respond to beta-adrenergic stimulation. CONCLUSIONS: Phentolamine or FK506 treatment during reperfusion improves alveolar liquid clearance and decreases the severity of lung injury.

Involvement of cytoskeletal integrity in the regulation of Cl- and amylase secretion from rat parotid acinar cells.

The cytoskeleton serves as a signal modulator for Ca2+ and cAMP-regulated cell functions including the secretion of ions and granule contents. The interaction between Ca2+ and cAMP signaling systems potentiates amylase secretion and suppresses Cl- secretion in the parotid glands. In this study, we investigated the role of the cytoskeleton in the modulation of Cl- and amylase secretion from rat parotid acinar cells upon activation of each intracellular signaling system and their interaction. Cytochalasin D markedly inhibited the Ca2+-activated outwardly rectifying Cl- current at positive membrane potentials and carbachol (CCh)-induced Cl- currents in the whole-cell configuration at -80 mV, whereas colchicine enhanced Cl- currents. Cytochalasin D, but not colchicine, markedly inhibited CCh-induced Cl- secretion. Synergistic actions of CCh and forskolin on Cl- and amylase secretion were observed even in the presence of cytochalasin D. These results suggest that the synergistic effects of Ca2+ and cAMP signaling systems on amylase and Cl- secretion do not require actin filament integrity but that secretion by the two signals themselves does require actin filament integrity.

Suppression of carbachol-induced oscillatory Cl- secretion by forskolin in rat parotid and submandibular acinar cells.

Sympathetic stimulation induces weak salivation compared with parasympathetic stimulation. To clarify this phenomenon in salivary glands, we investigated cAMP-induced modulation of Ca(2+)-activated Cl(-) secretion from rat parotid and submandibular acinar cells because fluid secretion from salivary glands depends on the Cl(-) secretion. Carbachol (Cch), a Ca(2+)-increasing agent, induced hyperpolarization of the cells with oscillatory depolarization in the current clamp mode of the gramicidin-perforated patch recording. In the voltage clamp mode at -80 mV, Cch induced a bumetanide-sensitive oscillatory inward current, which was larger in rat submandibular acinar cells than in parotid acinar cells. Forskolin and IBMX, cAMP-increasing agents, did not induce any marked current, but they evoked a small nonoscillatory inward current in the presence of Cch and suppressed the Cch-induced oscillatory inward current in all parotid acinar cells and half (56%) of submandibular acinar cells. In the current clamp mode, forskolin + IBMX evoked a small nonoscillatory depolarization in the presence of Cch and reduced the amplitude of Cch-induced oscillatory depolarization in both acinar cells. The oscillatory inward current estimated at the depolarized membrane potential was suppressed by forskolin + IBMX. These results indicate that cAMP suppresses Ca(2+)-activated oscillatory Cl(-) secretion of parotid and submandibular acinar cells at -80 mV and possibly at the membrane potential during Cch stimulation. The suppression may result in the weak salivation induced by sympathetic stimulation.