Colorectal adenoma detection rate using texture and color enhancement imaging versus white light imaging with chromoendoscopy: a propensity score matching study.

BACKGROUND AND AIM: Few studies have evaluated the adenoma detection rate (ADR) of colonoscopy with texture and color enhancement imaging (TXI), a novel image-enhancing technology. This study compares the detection of colorectal polyps using TXI to that using white light imaging (WLI). METHODS: This single-center retrospective study used propensity-matched scoring based on the patients' baseline characteristics (age, sex, indication, bowel preparation, endoscopist, colonoscope type, and withdrawal time) to compare the results of patients who underwent chromoendoscopy using WLI or TXI at the Toyoshima Endoscopy Clinic. The differences in polyp detection rates and the mean number of detected polyps per colonoscopy were determined between the TXI and WLI groups. RESULTS: After propensity score matching, 1970 patients were enrolled into each imaging modality group. The mean patient age was 57.2 ± 12.5 years, and 44.5% of the cohort were men. The ADR was higher in the TXI group than in the WLI group (55.0% vs 49.4%, odds ratio: 1.25). High-risk ADR were more common in the TXI group than in the WLI group (17.6% vs 12.8%; OR: 1.45). The mean number of adenomas per colonoscopy (APC) was higher in the TXI group than in the WLI group (1.187 vs 0.943, OR: 1.12). APC with a flat morphology (1.093 vs 0.848, OR: 1.14) and APC of <6 mm (0.992 vs 0.757, OR: 1.16) were higher in the TXI group than in the WLI group. CONCLUSION: Compared to WLI, TXI improved the ADR in patients who underwent chromoendoscopy based on actual clinical data.

Feasibility of Colorectal Endoscopic Submucosal Dissection in Elderly Patients: The Impact of Sarcopenia.

INTRODUCTION: Colorectal cancer is a public health concern associated with high incidence rates. Sarcopenia is a known risk factor for postoperative complications, although an association between increased complications after colorectal endoscopic submucosal dissection (ESD) and sarcopenia remains undocumented. Herein, we aimed to explore the feasibility of colorectal ESD in patients with sarcopenia. METHODS: This retrospective study included 499 patients (69 with and 430 without sarcopenia). We evaluated the short- and long-term outcomes of colorectal ESD. RESULTS: There were no significant differences between the two groups regarding en bloc, R0, or curative resection rates. However, poor bowel preparation was significantly more common in the sarcopenia group. Moreover, patients with sarcopenia exhibited a significant increase in complications (37.7% vs. 10.5%). Multivariate analysis revealed that sarcopenia (odds ratio [OR]: 3.78, 95% confidence interval [Cl]: 1.85-7.73, p < 0.001), anticoagulation therapy (OR: 3.59, 95% Cl: 1.86-6.92, p < 0.001), procedure time (OR: 1.28, 95% Cl: 1.11-1.47, p < 0.001), and resection size (OR: 1.25, 95% Cl: 1.03-1.52, p = 0.02) were significantly correlated with the Common Terminology Criteria for Adverse Events (CTCAE) ≥ grade 2. The correlation between sarcopenia and CTCAE ≥ grade 2 was maintained after matching, resulting in more extended hospital stays in patients with sarcopenia. However, we detected no association between sarcopenia and overall survival and ESD-related death. CONCLUSION: Sarcopenia is a risk factor for complications in colorectal ESD, suggesting that colorectal ESD could be performed for patients with sarcopenia, although much caution should be taken.

Transcriptome analysis reveals the essential role of NK2 homeobox 1/thyroid transcription factor 1 (NKX2-1/TTF-1) in gastric adenocarcinoma of fundic-gland type.

BACKGROUND: Gastric adenocarcinoma of fundic-gland type (GA-FG) is a gastric malignancy with little relation to Helicobacter pylori. Clinical characteristics of GA-FG have been established, but molecular mechanisms leading to tumorigenesis have not yet been elucidated. METHODS: We subjected three GA-FG tumors-normal mucosa pairs to microarray analysis. Network analysis was performed for the top 30 up-regulated gene transcripts, followed by immunohistochemical staining to confirm the gene expression analysis results. AGS and NUGC4 cells were transfected with the gene-encoding NK2 homeobox 1/thyroid transcription factor 1 (NKX2-1/TTF-1) to evaluate transcriptional changes in its target genes. RESULTS: Comprehensive gene expression analysis identified 1410 up-regulated and 1395 down-regulated gene probes with ≥ two-fold difference in expression. Among the top 30 up-regulated genes in GA-FG, we identified transcription factor NKX2-1/TTF-1, a master regulator of lung/thyroid differentiation, together with surfactant protein B (SFTPB), SFTPC, and secretoglobin family 3A member 2(SCGB3A2), which are regulated by NKX2-1/TTF-1. Immunohistochemical analysis of 16 GA-FG specimens demonstrated significantly higher NKX2-1/TTF-1 and SFTPB levels, as compared to that in adjacent normal mucosa (P < 0.05), while SCGB3A2 levels did not differ (P = 0.341). Transduction of NKX2-1/TTF-1 into AGS and NUGC4 cells induced transactivation of SFTPB and SFTPC, indicating that NKX2-1/TTF-1 can function as normally in gastric cells as it can in the lung cells. CONCLUSIONS: Our first transcriptome analysis of GA-FG indicates significant expression of NKX2-1/TTF1 in GA-FG. Immunohistochemistry and cell biology show ectopic expression and normal transactivation ability of NKX2-1/TTF-1, suggesting that it plays an essential role in GA-FG development.

Reduced DEFA5 Expression and STAT3 Activation Underlie the Submucosal Invasion of Early Gastric Cancers.

INTRODUCTION: Submucosal invasion is a core hallmark of early gastric cancer (EGC) with poor prognosis. However, the molecular mechanism of the progression from intramucosal gastric cancer (IMGC) to early submucosal-invasive gastric cancer (SMGC) is not fully understood. The objective of this study was to identify genes and pathways involved in the submucosal invasion in EGC using comprehensive gene expression analysis. METHODS: Gene expression profiling was performed for eight cases of IMGC and eight cases of early SMGC with submucosal invasion ≥500 µm. To validate the findings of gene expression analysis and to examine the gene expression pattern in tissues, immunohistochemical (IHC) staining was performed for 50 cases of IMGC and SMGC each. RESULTS: Gene expression analysis demonstrated that the expression levels of small intestine-specific genes were significantly decreased in SMGC. Among them, defensin alpha 5 (DEFA5) was the most downregulated gene in SMGC, which was further validated in SMGC tissues by IHC staining. Gene set enrichment analysis showed a strong association between SMGC, the JAK-STAT signaling pathway, and the upregulation of STAT3-activating cytokines. The expression of phosphorylated STAT3 was significant in the nucleus of tumor cells in SMGC tissues but not in areas expressing DEFA5. CONCLUSION: The results of this study strongly suggest that the downregulation of DEFA5 and the activation of STAT3 play a significant role in the submucosal invasion of EGC.

Risk factors for incomplete resection with pharyngeal endoscopic submucosal dissection and long-term prognosis after resection.

BACKGROUND: Advances in endoscopic imaging technology have led to an increase in detection of superficial pharyngeal squamous carcinoma. Endoscopic submucosal dissection (ESD) has been reported to be effective for the treatment of these lesions, however there is still insufficient evidence on the long-term results of pharyngeal ESD. METHODS: This is a single-center retrospective study of all cases of superficial pharyngeal cancer that underwent ESD as primary treatment between January 2010 and May 2022. A total of 83 lesions in 63 patients were analyzed. RESULTS: The en bloc resection rate was 100%, and R0 resection rate was 59.0%, with an adverse event rate of 6.0%. During a mean observation period of 1134 days, there were 0 cases of disease-specific metastasis or death. However, the 5-year cumulative incidence of metachronous head and neck cancer after resection was 27.1% and the 5-year overall survival and 10-year overall survival after pharyngeal ESD were 87.0% and 69.6%, respectively. Of the 34 cases with non-R0 resection, local recurrence occurred in 8.8%. Location of lesion (p = 0.011), disparity between demarcation of the lesion with NBI and iodine staining (p = 0.026), and non-effective laryngeal elevation (p = 0.080) were risk factors for non-R0 resection. CONCLUSION: Pharyngeal ESD is effective and safe. Further studies are needed to improve and standardize indications and strategies for pharyngeal ESD.

Repeated steroid injection and polyglycolic acid shielding for prevention of refractory esophageal stricture.

BACKGROUND: Postoperative stricture and refractory stricture are severe adverse events which occur after expansive esophageal endoscopic submucosal dissection (ESD). The aim of this study was to assess the efficacy of steroid injection, polyglycolic acid (PGA) shielding, and of additional steroid injection thereafter for the prevention of refractory esophageal stricture. METHODS: This is a retrospective cohort study of 816 consecutive cases of esophageal ESD performed between 2002 and 2021 at the University of Tokyo Hospital. After 2013, all patients with a diagnosis of superficial esophageal carcinoma covering over 1/2 the esophageal circumference underwent preventive treatment immediately after ESD with either "PGA shielding", "steroid injection", or "steroid injection + PGA shielding". Additional steroid injection was performed for high-risk patients after 2019. RESULTS: The risk of refractory stricture was especially high in the cervical esophagus (OR 24.77, p = 0.002) and after total circumferential resection (OR 894.04, p < 0.001). "Steroid injection + PGA shielding" was the only method significantly effective in preventing stricture occurrence (OR 0.36; 95% CI 0.15-0.83, p = 0.012). This method also decreased the risk of refractory stricture (OR 0.38; 95% CI 0.10-1.28, p = 0.096), but additional steroid injection was the only significantly effective method for prevention of refractory stricture (OR 0.42; 95% CI 0.14-0.98, p = 0.029). CONCLUSION: Combining steroid injection and PGA shielding is effective for preventing post-ESD stricture and refractory stricture. Additional steroid injection is a viable option for patients at high-risk for refractory stricture.

Axin2+ Peribiliary Glands in the Periampullary Region Generate Biliary Epithelial Stem Cells That Give Rise to Ampullary Carcinoma.

BACKGROUND & AIMS: Peribiliary glands (PBGs), clusters of epithelial cells residing in the submucosal compartment of extrahepatic bile ducts, have been suggested as biliary epithelial stem/progenitor cell niche; however, evidence to support this claim is limited because of a lack of PBG-specific markers. We therefore sought to identify PBG-specific markers to investigate the potential role of PBGs as stem/progenitor cell niches, as well as an origin of cancer. METHODS: We examined the expression pattern of the Wnt target gene Axin2 in extrahepatic bile ducts. We then applied lineage tracing to investigate whether Axin2-expressing cells from PBGs contribute to biliary regeneration and carcinogenesis using Axin2-CreERT mice. RESULTS: Wnt signaling activation, marked by Axin2, was limited to PBGs located in the periampullary region. Lineage tracing showed that Axin2-expressing periampullary PBG cells are capable of self-renewal and supplying new biliary epithelial cells (BECs) to the luminal surface. Additionally, the expression pattern of Axin2 and the mature ductal cell marker CK19 were mutually exclusive in periampullary region, and fate tracing of CK19+ luminal surface BECs showed gradual replacement by CK19- cells, further supporting the continuous replenishment of new BECs from PBGs to the luminal surface. We also found that Wnt signal enhancer R-spondin3 secreted from Myh11-expressing stromal cells, corresponding to human sphincter of Oddi, maintained the periampullary Wnt signal-activating niche. Notably, introduction of PTEN deletion into Axin2+ PBG cells, but not CK19+ luminal surface BECs, induced ampullary carcinoma whose development was suppressed by Wnt inhibitor. CONCLUSION: A specific cell population receiving Wnt-activating signal in periampullary PBGs functions as biliary epithelial stem/progenitor cells and also the cellular origin of ampullary carcinoma.

Involvement of small-conductance Ca2+-activated K+ (SKCa2) channels in spontaneous Ca2+ oscillations in rat pinealocytes.

Melatonin secretion from the pineal glands regulates circadian rhythms in mammals. Melatonin production is decreased by an increase in cytosolic Ca2+ concentration following the activation of nicotinic acetylcholine receptors in parasympathetic systems. We previously reported that pineal Ca2+ oscillations were regulated by voltage-dependent Ca2+ channels and large-conductance Ca2+-activated K+ (BKCa) channels, which inhibited melatonin production. In the present study, the contribution of small- and intermediate-conductance Ca2+-activated K+ (SKCa and IKCa) channels to the regulation of spontaneous Ca2+ oscillations was examined in rat pinealocytes. The amplitude and frequency of spontaneous Ca2+ oscillations were increased by a SKCa channel blocker (100 nM apamin), but not by an IKCa channel blocker (1 µM TRAM-34). On the other hand, they were decreased by a SKCa channel opener (100 µM DCEBIO), but not by an IKCa channel opener (1 µM DCEBIO). Expression analyses using quantitative real-time PCR, immunocytochemical staining, and Western blotting revealed that the SKCa2 channel subtype was abundantly expressed in rat pinealocytes. Moreover, the enhanced amplitude of Ca2+ oscillations in the presence of apamin was further increased by a BKCa channel blocker (1 µM paxilline). These results suggest that the activity of SKCa2 channels regulates cytosolic Ca2+ signaling and melatonin production during parasympathetic activation in pineal glands.

Analysis of Barrett's Esophagus and Its Risk Factors: A Cross-Sectional Study of 10,122 Subjects at a Japanese Health Examination Center.

INTRODUCTION: Helicobacter pylori eradication is expected to significantly change the prevalence of Barrett's esophagus (BE). However, few reports on this relationship exist. We analyzed the risk factors of BE using the current consensus on length of BE considering H. pylori infection status. METHODS: We analyzed 10,122 individuals (5,962 men; mean age = 52.9 ± 9.9 years) who had undergone esophagogastroduodenoscopy as part of a medical checkup. Correlations among factors including H. pylori infectious status, endoscopic findings, and BE ≥1 cm were analyzed. RESULTS: Prevalence of BE, long-segment BE, and esophageal adenocarcinoma was 22.5%, 0.014%, and 0%, respectively. Logistic regression analysis showed that the risk factors for BE were hiatal hernia (odds ratio [OR]: 2.89 [2.59-3.24]), female sex (OR: 0.52 [0.46-0.59]), social drinking (OR:0.77 [0.68-0.87]), H. pylori eradication therapy (OR: 1.34 [1.19-1.51]), proton pump inhibitor (PPI) use (OR: 1.52 [1.18-1.96]), bile reflux (OR: 1.18 [1.04-1.33]), age ≥50 years (OR: 1.13 [1.02-1.26]), and nonsteroidal anti-inflammatory drug (NSAID) use (OR: 1.29 [1.02-1.62]). Although reflux esophagitis (RE) was more common in H. pylori-negative patients (17.2%) than in those after H. pylori eradication therapy (11.8%, p < 0.00001), the latter was correlated with BE, disputing RE as a strong risk factor for BE. Therefore, we conducted a subgroup analysis; most of the risk factors except for PPI use (p = 0.75), H2-receptor antagonist use (p = 0.078), and atrophic gastritis absence (p = 0.72) were positively correlated with BE after H. pylori eradication therapy compared with H. pylori-negative status. CONCLUSIONS: H. pylori eradication, bile reflux, PPI use, and NSAID use were risk factors for BE along with hiatal hernia, male sex, and older age.

The impact of sarcopenia on adverse events associated with gastric endoscopic submucosal dissection.

BACKGROUND: Endoscopic submucosal dissection (ESD) is one of the main methods of treatments for early gastric cancer. Sarcopenia is a known risk factor for postoperative adverse events; however, the effect of sarcopenia on gastric ESD is unclear. We investigated the impact of sarcopenia on short-term prognosis after gastric ESD. METHODS: This was a retrospective cohort study. We reviewed 832 patients who underwent gastric ESD between January 2015 and December 2019 and classified them into two groups: sarcopenia and non-sarcopenia groups. The curative resection rate, adverse events, and lengths of hospital stay were evaluated. We also evaluated risk factors associated with adverse events. RESULTS: 700 patients were analyzed (239 in the sarcopenia group and 461 in the non-sarcopenia group). The curative resection rates were similar in both groups. Common Terminology Criteria for Adverse Events (CTCAE) grade ≥ 2 (17% vs. 10%) were significantly more common, and the length of hospital stay was longer (8 vs. 7 days) in the sarcopenia group. Univariate analysis identified age ≥ 75 years, antithrombotic medication, history of gastric surgery, submucosal (SM) invasion, and sarcopenia as risk factors for CTCAE grade ≥ 2. Multivariate analysis showed that sarcopenia [odds ratio (OR) 1.79, 95% confidence interval (CI) 1.11-2.89, p = 0.016], history of gastric surgery (OR 9.32, 95% CI 1.97-44.05, p = 0.005), and SM invasion (OR 2.14, 95% CI 1.24-3.70, p = 0.006) were significant independent risk factors. CONCLUSIONS: Sarcopenia significantly affected short-term prognosis and is a novel risk factor for gastric ESD.

TAS-303 Ameliorates Carbachol-Induced Detrusor Overactivity in Rats, Revealing Its Therapeutic Potential for Overactive Bladder.

Urinary incontinence is defined as an involuntary leakage of urine and is categorized into three types: stress urinary incontinence (SUI), urge urinary incontinence (UUI), and mixed urinary incontinence, which includes symptoms of SUI and UUI. As the underlying mechanisms of SUI and UUI are different, no drug is approved to treat all three types of urinary incontinence. TAS-303 is a selective norepinephrine reuptake inhibitor and has therapeutic potential for patients with SUI. In this report, we describe newly discovered pharmacological properties of TAS-303 and its effects on bladder function. Radioligand binding studies showed that TAS-303 inhibits M3 muscarinic receptor binding, with a Ki value of 547 nM. TAS-303 at 1, 3, and 10 mg/kg dose-dependently prolonged the intercontraction interval of carbachol-induced detrusor overactivity in rats, exhibiting a maximal effect that was comparable to tolterodine. These effects may result from coordinated regulation of bladder afferent activity via M3 muscarinic inhibition and ß3 adrenoreceptor activation by norepinephrine elevation due to norepinephrine transporter inhibition. Moreover, TAS-303 at the effective dose for bladder function did not induce dry mouth or constipation in rats, showing that this compound may have a lower risk of antimuscarinic side effects. Thus, TAS-303 is expected to be a new profile agent with therapeutic potential for all types of urinary incontinence. SIGNIFICANCE STATEMENT: Urinary incontinence is categorized into stress, urge, and mixed urinary incontinence, but because the underlying mechanisms of each differ, no drugs are available that treat all three. TAS-303 has therapeutic potential for stress urinary incontinence. This study describes newly discovered pharmacological properties of TAS-303, which ameliorated bladder afferent activity partly via M3 muscarinic inhibition, indicating improvement in urge urinary incontinence, and highlights the potential of TAS-303 as a new therapeutic agent for all types of urinary incontinence.

Steroid injection and polyglycolic acid shielding to prevent stricture after esophageal endoscopic submucosal dissection: a retrospective comparative analysis (with video).

BACKGROUND AND AIMS: Postoperative stricture after expansive esophageal endoscopic submucosal dissection (ESD) is a severe adverse event. Previous single-arm reports have suggested that polyglycolic acid (PGA) shielding may prevent stricture. This study was performed to assess the efficacy of this method through a comparative analysis. METHODS: This is a retrospective analysis of 500 consecutive cases of esophageal ESD performed between 2002 and 2018 at the University of Tokyo Hospital. After 2013, patients with a diagnosis of superficial esophageal carcinoma covering more than half of the esophageal circumference underwent preventive treatment with either PGA shielding or steroid injection + PGA shielding after ESD. The efficacy of these methods for preventing post-ESD stricture was assessed through multivariable logistic regression analysis. RESULTS: The risk of postoperative stricture was especially high in the cervical esophagus (odds ratio [OR], 4.60; 95% confidence interval [CI], 0.65-61.09) and after total circumferential resection (OR, 3.58×103; lower bound of 95% CI, >185). Steroid injection + PGA shielding was the only method significantly effective in preventing stricture (OR, 0.30; 95% CI, 0.10-0.78; P = .009). In the relatively low-risk subgroup (excluding cervical esophageal cancer and complete circumferential resection), the postoperative stricture rates for steroid injection + PGA shielding versus PGA shielding versus control were 18.9% versus 41.4% versus 51.7%, respectively (P = .015). However, the efficacy of this was limited in extremely high-risk cases. CONCLUSION: The combination of steroid injection and PGA shielding is effective for preventing post-ESD stricture. There is a need for even more effective methods for cervical esophageal cancer and complete circumferential resection.

TAS-303, a Novel Selective Norepinephrine Reuptake Inhibitor that Increases Urethral Pressure in Rats, Indicating Its Potential as a Therapeutic Agent for Stress Urinary Incontinence.

Stress urinary incontinence (SUI) is characterized by involuntary leakage associated with exertion, effort, sneezing, coughing, or lifting. Duloxetine, a serotonin norepinephrine reuptake inhibitor, is approved for the treatment of patients with SUI in some European countries, but not in the United States. There is currently no globally approved pharmacological drug for the treatment of patients with SUI. Therefore, a new pharmacological treatment option is required. TAS-303 [4-piperidinyl 2,2-diphenyl-2-(propoxy-1,1,2,2,3,3,3-day7 )acetate hydrochloride] is a novel small-molecule selective norepinephrine reuptake inhibitor that displays significant norepinephrine transporter (NET) inhibitory activity toward the serotonin or dopamine transporters. In this report, we describe the pharmacological properties of TAS-303 and its effects on urethral function, using preclinical in vitro and in vivo studies. Radioligand-binding studies showed that TAS-303 selectively and potently inhibited [3H]norepinephrine binding to the human NET. Oral administration of TAS-303 (3 mg/kg) significantly increased norepinephrine levels in the plasma, whereas it did not significantly affect epinephrine, dopamine, and serotonin levels. TAS-303 (0.3, 1, and 3 mg/kg) dose-dependently increased basal urethral pressure in normal rats and leak point pressure in vaginal distention rats, exhibiting a maximal effect comparable to duloxetine. In the forced swimming test, TAS-303 (100 mg/kg) showed no significant effects on immobility time in rats, raising the possibility that this agent would have minimal central nervous system side effects at an effective dose for urethral function. These results demonstrate that TAS-303 has therapeutic potential for the treatment of patients with SUI.

Transparency-enhancing technology allows three-dimensional assessment of gastrointestinal mucosa: A porcine model.

Although high-resolution three-dimensional imaging of endoscopically resected gastrointestinal specimens can help elucidating morphological features of gastrointestinal mucosa or tumor, there are no established methods to achieve this without breaking specimens apart. We evaluated the utility of transparency-enhancing technology for three-dimensional assessment of gastrointestinal mucosa in porcine models. Esophagus, stomach, and colon mucosa samples obtained from a sacrificed swine were formalin-fixed and paraffin-embedded, and subsequently deparaffinized for analysis. The samples were fluorescently stained, optically cleared using transparency-enhancing technology: ilLUmination of Cleared organs to IDentify target molecules method (LUCID), and visualized using laser scanning microscopy. After observation, all specimens were paraffin-embedded again and evaluated by conventional histopathological assessment to measure the impact of transparency-enhancing procedures. As a result, microscopic observation revealed horizontal section views of mucosa at deeper levels and enabled the three-dimensional image reconstruction of glandular and vascular structures. Besides, paraffin-embedded specimens after transparency-enhancing procedures were all assessed appropriately by conventional histopathological staining. These results suggest that transparency-enhancing technology may be feasible for clinical application and enable the three-dimensional structural analysis of endoscopic resected specimen non-destructively. Although there remain many limitations or problems to be solved, this promising technology might represent a novel histopathological method for evaluating gastrointestinal cancers.

Modulation of Ca2+ oscillation and melatonin secretion by BKCa channel activity in rat pinealocytes.

The pineal glands regulate circadian rhythm through the synthesis and secretion of melatonin. The stimulation of nicotinic acetylcholine receptor due to parasympathetic nerve activity causes an increase in intracellular Ca(2+) concentration and eventually downregulates melatonin production. Our previous report shows that rat pinealocytes have spontaneous and nicotine-induced Ca(2+) oscillations that are evoked by membrane depolarization followed by Ca(2+) influx through voltage-dependent Ca(2+) channels (VDCCs). These Ca(2+) oscillations are supposed to contribute to the inhibitory mechanism of melatonin secretion. Here we examined the involvement of large-conductance Ca(2+)-activated K(+) (BKCa) channel conductance on the regulation of Ca(2+) oscillation and melatonin production in rat pinealocytes. Spontaneous Ca(2+) oscillations were markedly enhanced by BKCa channel blockers (1 µM paxilline or 100 nM iberiotoxin). Nicotine (100 µM)-induced Ca(2+) oscillations were also augmented by paxilline. In contrast, spontaneous Ca(2+) oscillations were abolished by BKCa channel opener [3 µM 12,14-dichlorodehydroabietic acid (diCl-DHAA)]. Under whole cell voltage-clamp configurations, depolarization-elicited outward currents were significantly activated by diCl-DHAA and blocked by paxilline. Expression analyses revealed that the α and ß3 subunits of BKCa channel were highly expressed in rat pinealocytes. Importantly, the activity of BKCa channels modulated melatonin secretion from whole pineal gland of the rat. Taken together, BKCa channel activation attenuates these Ca(2+) oscillations due to depolarization-synchronized Ca(2+) influx through VDCCs and results in a recovery of reduced melatonin secretion during parasympathetic nerve activity. BKCa channels may play a physiological role for melatonin production via a negative-feedback mechanism.

Spontaneous and nicotine-induced Ca2+ oscillations mediated by Ca2+ influx in rat pinealocytes.

The pineal gland regulates circadian rhythm through the synthesis and secretion of melatonin. The rise of intracellular Ca(2+) concentration ([Ca(2+)]i) following nicotinic acetylcholine receptor (nAChR) stimulation due to parasympathetic nerve activity downregulates melatonin production. Important characteristics and roles of Ca(2+) mobilization due to nAChR stimulation remain to be clarified. We report here that spontaneous Ca(2+) oscillations can be observed in ∼15% of the pinealocytes in slice preparations from rat pineal glands when this dissociation procedure is done within 6 h from a dark-to-light change. The frequency and half-life of [Ca(2+)]i rise were 0.86 min(-1) and 19 s, respectively. Similar spontaneous Ca(2+) oscillations were recorded in 17% of rat pinealocytes that were primary cultured for several days. Simultaneous measurement of [Ca(2+)]i and membrane potential revealed that spontaneous Ca(2+) oscillations were triggered by periodic membrane depolarizations. Spontaneous Ca(2+) oscillations in cultured pinealocytes were abolished by extracellular Ca(2+) removal or application of nifedipine, a blocker of voltage-dependent Ca(2+) channel (VDCC). In contrast, blockers of intracellular Ca(2+)-release channels, 2-aminoethoxydiphenylborate and ryanodine, have no effect. Our results also reveal that, in 23% quiescent pinealocytes, Ca(2+) oscillations were observed following the withdrawal of nicotine. Norepinephrine-induced melatonin secretion from whole pineal glands was significantly decreased by the coapplication of acetylcholine (ACh). This inhibitory effect of ACh was attenuated by nifedipine. In conclusion, both spontaneous and evoked Ca(2+) oscillations are due to membrane depolarization following activation of VDCCs. This consists of VDCC α1F subunit, and the associated Ca(2+) influx can strongly regulate melatonin secretion in pineal glands.