Retrospective cohort study investigating association between precancerous gastric lesions and colorectal neoplasm risk.

Background: Colorectal cancer (CRC) is considered the most prevalent synchronous malignancy in patients with gastric cancer. This large retrospective study aims to clarify correlations between gastric histopathology stages and risks of specific colorectal neoplasms, to optimize screening and reduce preventable CRC. Methods: Clinical data of 36,708 patients undergoing gastroscopy and colonoscopy from 2005-2022 were retrospectively analyzed. Correlations between gastric and colorectal histopathology were assessed by multivariate analysis. Outcomes of interest included non-adenomatous polyps (NAP), conventional adenomas (CAs), serrated polyps (SPs), and CRC. Statistical analysis used R version 4.0.4. Results: Older age (≥50 years) and Helicobacter pylori infection (HPI) were associated with increased risks of conventional adenomas (CAs), serrated polyps (SPs), non-adenomatous polyps (NAP), and colorectal cancer (CRC). Moderate to severe intestinal metaplasia specifically increased risks of NAP and CAs by 1.17-fold (95% CI 1.05-1.3) and 1.19-fold (95% CI 1.09-1.31), respectively. For CRC risk, low-grade intraepithelial neoplasia increased risk by 1.41-fold (95% CI 1.08-1.84), while high-grade intraepithelial neoplasia (OR 3.76, 95% CI 2.25-6.29) and gastric cancer (OR 4.81, 95% CI 3.25-7.09) showed strong associations. More advanced gastric pathology was correlated with progressively higher risks of CRC. Conclusion: Precancerous gastric conditions are associated with increased colorectal neoplasm risk. Our findings can inform screening guidelines to target high-risk subgroups, advancing colorectal cancer prevention and reducing disease burden.

Same-day single-dose vs large-volume split-dose regimens of polyethylene glycol for bowel preparation: A systematic review and meta-analysis.

BACKGROUND: Split-dose regimens (SpDs) of 4 L of polyethylene glycol (PEG) have been established as the "gold standard" for bowel preparation; however, its use is limited by the large volumes of fluids required and sleep disturbance associated with night doses. Meanwhile, the same-day single-dose regimens (SSDs) of PEG has been recommended as an alternative; however, its superiority compared to other regimens is a matter of debate. AIM: To compare the efficacy and tolerability between SSDs and large-volume SpDs PEG for bowel preparation. METHODS: We searched MEDLINE/PubMed, the Cochrane Library, RCA, EMBASE and Science Citation Index Expanded for randomized trials comparing (2 L/4 L) SSDs to large-volume (4 L/3 L) SpDs PEG-based regimens, regardless of adjuvant laxative use. The pooled analysis of relative risk ratio and mean difference was calculated for bowel cleanliness, sleep disturbance, willingness to repeat the procedure using the same preparation and adverse effects. A random effects model or fixed-effects model was chosen based on heterogeneity analysis among studies. RESULTS: A total of 18 studies were included. There was no statistically significant difference of adequate bowel preparation (relative risk = 0.97; 95%CI: 0.92-1.02) (14 trials), right colon Boston Bowel Preparation Scale (mean difference = 0.00; 95%CI: -0.04, 0.03) (9 trials) and right colon Ottawa Bowel Preparation Scale (mean difference = 0.04; 95%CI: -0.27, 0.34) (5 trials) between (2 L/4 L) SSDs and large-volume (4 L/3 L) SpDs, regardless of adjuvant laxative use. The pooled analysis favored the use of SSDs with less sleep disturbance (relative risk = 0.52; 95%CI: 0.40, 0.68) and lower incidence of abdominal pain (relative risk = 0.75; 95%CI: 0.62, 0.90). During subgroup analysis, patients that received low-volume (2 L) SSDs showed more willingness to repeat the procedure using the same preparation than SpDs (P < 0.05). No significant difference in adverse effects, including nausea, vomiting and bloating, was found between the two arms (P > 0.05). CONCLUSION: Regardless of adjuvant laxative use, the (2 L/4 L) SSD PEG-based arm was considered equal or better than the large-volume (≥ 3 L) SpDs PEG regimen in terms of bowel cleanliness and tolerability. Patients that received low-volume (2 L) SSDs showed more willingness to repeat the procedure using the same preparation due to the low-volume fluid requirement and less sleep disturbance.

An Analysis of the Correlation Between Clinical Indexes and Pathological Classifications in 202 Patients with Lupus Nephritis.

OBJECTIVE: To investigate the correlation between clinical indexes and pathological classifications in 202 patients with lupus nephritis (LN). METHODS: A total of 202 LN cases were retrospectively analyzed. All these patients met the four diagnostic criteria for systemic lupus erythematosus (SLE) of the American College of Rheumatology revised in 1997. The pathological diagnostic criteria of LN were in accordance with the pathological LN classification revised by the International Society of Nephrology and the Society of Kidney Pathology in 2003. The patients were scored according to the improved SLE Disease Activity Index 2000 (SLEDAI-2K), and their basic data, clinical data, laboratory data, and pathological data were collected. RESULTS: Among the 202 patients, the ratio of male to female was 1:5.73, and type IV was the most common pathological LN classification. There were differences in the urine analysis, hypertension incidence, blood cell analysis, blood lipids, renal function, plasma albumin, immunological indexes, renal pathological score among the different pathological types (P < 0.05). In the early finding of renal function damage of the patients, cystatin C sensitivity was significantly higher than that of serum creatinine and blood urea nitrogen. Multiple linear regression analysis show that there are strong correlations between AI and SLEDAI, 24hU-Pr, serum C3, serum ALB, BUN, creatinine, UA and PLT (P < 0.001); and there are correlations between AI and serum IgM, IgA, C4, TC and LDL-C (P < 0.05). CONCLUSION: There is a clear correlation between pathological classifications and clinical indexes of LN. TRIAL REGISTRATION: Shen-PJ-2018-40, Study on Clinical and Molecular Mechanism of SLE.

Effect of temperature maintenance by forced-air warming blankets of different temperatures on changes in inflammatory factors in children undergoing congenital hip dislocation surgery.

BACKGROUND: Hypothermia is associated with many adverse clinical outcomes in pediatric patients, and thus, it is important to find an effective and safe method for preventing peri-operative hypothermia and its associated adverse outcomes in pediatric patients. This study aimed to investigate the effect of forced-air warming blankets with different temperatures on changes in the transforming growth factor-ß (TGF-ß), tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-10 levels in children undergoing surgical treatment for developmental displacement of the hip (DDH). METHODS: The study included 123 children undergoing surgery for DDH under general anesthesia. The patients were randomly assigned to three groups, using a random number table: the 32, 38, and 43°C groups according to the temperature setting of the forced-air warming blankets. For each patient, body temperature was recorded immediately after anesthesia induction and intubation (T0), at initial incision (T1), at 1 h after incision (T2), at 2 h after incision (T3), at the end of surgery (T4), immediately upon return to the ward after surgery (T5), and then at 12 h (T6), 24 h (T7), 36 h (T8), and 48 h (T9) after the surgery. The serum levels of TGF-ß, TNF-α, IL-1ß, and IL-10 were measured at T0 and T4 for all groups. RESULTS: The number of patients with fever in the 38°C group was significantly less than those in the 32 and 43°C groups (χ = 6.630, P = 0.036). At T0, the body temperatures in the 38 and 43°C groups were significantly higher than that in the 32°C group (F = 17.992, P < 0.001). At T2, the body temperature was significantly higher in the 43°C group than those in the 32 and 38°C groups (F = 12.776, P < 0.001). Moreover, at T4, the serum levels of TGF-ß (F = 3286.548, P < 0.001) and IL-10 (F = 4628.983, P < 0.001) were significantly increased in the 38°C group, and the serum levels of TNF-α (F = 911.415, P < 0.001) and IL-1ß (F = 322.191, P < 0.001) were significantly decreased in the 38°C group, compared with the levels in the 32 and 43°C groups. CONCLUSION: Force-air warming blankets set at 38°C maintained stable body temperature with less adverse outcome and effectively inhibited the inflammatory response in pediatric patients undergoing surgery for DDH. CLINICAL TRIAL REGISTRATION: ChiCTR1800014820; http://www.chictr.org.cn/showproj.aspx?proj=25240.

HIV infection confers distinct mechanisms in severe drug eruption: Endogenous virus activation with aberrant Th2/Th1 and CD8+ T cells function.

Severe drug eruption (SDE), a common skin disease, becomes dangerous when it occurs in patients with human immunodeficiency virus (HIV). However, the molecular mechanisms are poorly understood. Forty patients including HIV+ SDE+ (n = 15), HIV- SDE+ (n = 15) and HIV+ SDE- (n = 10) subjects were enrolled in our study. All HIV+ patients were at acquired immune deficiency syndrome (AIDS) stage. Serum levels of TNF-α, IFN-γ, IL-4, IL-13, IL-6, CXCL9, and CCL17 were quantified by ELISA. Epstein-Barr virus (EBV) and cytomegalovirus (CMV) loads were quantified by RT-qPCR. CD4, CD8, Th1, Th2, TNF-α-CD8, and IFN-γ-CD8 T cell populations were measured by flow cytometry. Levels of biochemical indexes in HIV+ SDE+ patients were significantly different from in HIV- SDE+ patients (P < .05). EBV and CMV viral loads were significantly higher in HIV+ SDE+ patients, but not in HIV- SDE+ patients (P < .05). Inflammatory cytokines TNF-α and IFN-γ were significantly elevated in HIV+ SDE+ patients (P < .05). Th2/Th1 populations and TNF-α secreting or IFN-γ secreting CD8+ T cells, were significantly up-regulated in HIV+ SDE+ patients compared to HIV- SDE+ patients (P < .05). Conversely, the CD4/CD8 ratio was significantly down-regulated in HIV+ SDE+ patients compared to HIV- SDE+ patients (P < .05). HIV infection confers distinct clinical phenotypes and immune inflammatory mechanisms in SDE. Sustained EBV and CMV activation, unbalanced Th2/Th1 and overactive CD8+ T cells mediating a pro-inflammatory response could act as distinct mechanisms in the aggravation of SDE in HIV+ SDE+ patients.

Abnormally expressed miR-23b in Chinese Mongolian at high cardiovascular risk may contribute to monocyte/macrophage inflammatory reaction in atherosclerosis.

Background: The prevalence of coronary heart disease (CHD) appears to be high among Chinese Mongolians. MiR-23b has been proven to play a key role in atherosclerosis. The expression and role of miR-23b in the Mongolians at high cardiovascular risk were explored in the present study.Methods: Forty cases of blood samples from the Mongolians at high cardiovascular risk were enrolled in the present study. The expression of miR-23b was quantified by quantitative real-time PCR. To induce monocytes differentiation into macrophages, HP-1 cells were cultured with phorbol 12-myristate 13-acetate. The level of inflammatory markers was determined by the enzyme-linked immunosorbent assay. The interaction between miR-23b and A20 was explored by the dual luciferase reporter assay.Results: The expression of miR-23b in the Mongolian at high cardiovascular risk was higher than that in healthy Mongolian volunteers. Decrease in ATP-binding cassette transporter A1 caused by miR-23b is responsible for TC accumulation in the Mongolian at high cardiovascular risk. MiR-23b enhanced the oxidized low-density lipoprotein (oxLDL)-induced inflammatory response of THP-1 derived macrophage. MiR-23b regulated nuclear factor-κB (NF-κB) pathway through targeting A20. MiR-23b mediated oxLDL-induced inflammatory response of peripheral blood mononuclear cell in the Mongolian at high cardiovascular risk.Conclusion MiR-23b enhanced oxLDL-induced inflammatory response of macrophages in the Mongolian at high cardiovascular risk through the A20/NF-κB signaling pathway, and thus contributing to atherosclerosis.

Magnifying narrow-band imaging endoscopy is superior in diagnosis of early gastric cancer.

AIM: To evaluate the diagnostic effectiveness of white light endoscopy, magnifying endoscopy (ME), and magnifying narrow-band imaging endoscopy (ME-NBI) in detecting early gastric cancer (EGC). METHODS: From March 2010 to June 2012, a total of 3616 patients received screening for gastric cancer by magnifying endoscopy. There were 3675 focal gastric lesions detected using conventional high definition white light endoscopy (HD-WLE) in four different referential hospitals that were recruited for further investigation using ME and ME-NBI. The images obtained from HD-WLE, ME, and ME-NBI were reviewed by four experienced endoscopists to evaluate their diagnostic effectiveness for EGC. The diagnosis of cancerous and non-cancerous lesions was conducted by evaluating the microvascular and microsurface patterns using the VS classification system. The final endoscopic diagnosis of each lesion was determined by consultation when a disagreement occurred. We used histopathological results as the gold standard for the diagnosis of EGC. RESULTS: Among the 3675 lesions found, 1508 were validated by pathological findings as chronic gastritis, 1279 as chronic gastritis with intestinal metaplasia, 631 as low-grade neoplasia, and 257 as EGC. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of HD-WLE for the diagnosis of EGC were 71.2%, 99.1%, 85.5%, 97.9% and 97.1%, respectively. The results of ME for diagnosing EGC were 81.3%, 98.8%, 83.3%, 98.6% and 97.6%, respectively. The results of ME-NBI for the diagnosis of EGC were 87.2%, 98.6%, 82.1%, 99.0% and 97.8%, respectively. The diagnostic sensitivity and accuracy of paired ME and ME-NBI were significantly better than those of HD-WLE (P < 0.05). CONCLUSION: HD-WLE has a relatively high accuracy for diagnosing EGC and is an effective screening tool. Further investigations of ME and ME-NBI are required to achieve superior accuracy.

[Characteristics of 72 h glucose profiles detected by continuous glucose monitoring system in patients with insulinoma].

OBJECTIVE: To identify the characteristics of glucose profiles in patients with insulinoma using continuous glucose monitoring system (CGMS). METHODS: Six patients with insulinoma (All of the patients were diagnosed after operations with pathological tests) admitted to the Department of Endocrinology and Metabolism, West China Hospital of Sichuan University from October 2009 to November 2011 were recruited for this study (group A). They were compared with 71 patients with normal glucose tolerance (NGT) (group B) and 3 patients with responsive hypoglycemia (group C). All of the participants received 75 g oral glucose tolerance tests (OGTT), insulin release tests, and 72 h CGM. Glucose fluctuations and hypoglycemia risks were assessed by the following parameters obtained from CGMS: mean blood glucose (MBG) and standard deviation (SD), mean amplitude of glycemic excursion (MAGE), mean daily differences (MODD), low glucose index (LBGI), glycaemic Risk Assessment Diabetes Equation (GRADE) and M-value. RESULTS: Group A had significantly lower levels of HbA1c, fasting blood glucose, and 2 h-BG than group B (P < 0.05). Compared with Group B, Group A had lower levels of 72 h-MBG (P < 0.001) and higher levels of LBGI, M-value, GRADE, SD and MODD (P < 0.05). The insulinoma patients had 27 occasions of hypoglycemia (glucose < 2.8 mmol/L), more likely in early morning, at a fasting state or preprandial periods. Such events were rare in the control groups (2 occasions in Group B and one occasion in Group C). CONCLUSION: Insulinoma patients present a greater level of glucose fluctuations and frequent hypoglycemia. Hypoglycemia risk detected by CGM is helpful for differentiating diagnosis of insulinoma.

Derivation and validation of a prediction rule for estimating advanced colorectal neoplasm risk in average-risk Chinese.

No prediction rule is currently available for advanced colorectal neoplasms, defined as invasive cancer, an adenoma of 10 mm or more, a villous adenoma, or an adenoma with high-grade dysplasia, in average-risk Chinese. In this study between 2006 and 2008, a total of 7,541 average-risk Chinese persons aged 40 years or older who had complete colonoscopy were included. The derivation and validation cohorts consisted of 5,229 and 2,312 persons, respectively. A prediction rule was developed from a logistic regression model and then internally and externally validated. The prediction rule comprised 8 variables (age, sex, smoking, diabetes mellitus, green vegetables, pickled food, fried food, and white meat), with scores ranging from 0 to 14. Among the participants with low-risk (≤3) or high-risk (>3) scores in the validation cohort, the risks of advanced neoplasms were 2.6% and 10.0% (P < 0.001), respectively. If colonoscopy was used only for persons with high risk, 80.3% of persons with advanced neoplasms would be detected while the number of colonoscopies would be reduced by 49.2%. The prediction rule had good discrimination (area under the receiver operating characteristic curve = 0.74, 95% confidence interval: 0.70, 0.78) and calibration (P = 0.77) and, thus, provides accurate risk stratification for advanced neoplasms in average-risk Chinese.

Mesenchymal stem cells stimulate protective genetic reprogramming of injured cardiac ventricular myocytes.

Since massive irreversible loss of cardiac myocytes occurs following myocardial injury, injection of human mesenchymal stem cells (hMSCs) has emerged as a promising therapeutic intervention. Despite the growing enthusiasm for this approach, the understanding of how hMSCs evoke cardiac improvement is ever more controversial. The present study critically tests hypothesis that hMSCs provide specific benefit directly to damaged ventricular myocytes. Cultures of neonatal mouse ventricular cardiac myocytes (nMCM) were subjected to two distinct acute stress protocols; incubations with either endotoxin, lipopolysaccharide (LPS) or toxic cytokine, IL-1ß. Myocyte injury was assessed in intracellular Ca(2+) signaling assays in fluo-3-loaded nMCMs that were imaged with high temporal resolution by fluorescent microscopy. Following LPS or IL-1ß treatment there was profound myocyte injury, manifest by chaotic [Ca(2+)](i) handling, quantified as a 3- to 5-fold increase in spontaneous [Ca(2+)](i) transients. Antibody neutralization experiments reveal such damage is mediated in part by interleukin-18 and not by tumor necrosis factor-α (TNF-α). Importantly, normal [Ca(2+)](i) signaling was preserved when cardiomyocytes were co-cultured with hMSCs. Since normal [Ca(2+)](i) handling was maintained in transwell cultures, where nMCMs and hMSCs were separated by a permeable membrane, a protective paracrine signaling cascade is operable. hMSCs provoke a genetic reprogramming of cardiomyocytes. LPS provokes release of TNFα from nMCMs which is blocked by hMSCs grown in co- or transwell cultures. Consistent with cytokine release, flow cytometry analyses reveal that hMSCs also block the LPS- and IL-1ß-dependent activation of cardiac transcription factor, NF-κB. Importantly, hMSC-conditioned medium restores normal Ca(2+) signaling in LPS- and IL-1ß-damaged nMCMs. These results reveal new evidence that hMSCs elicit protective and reparative effects on cardiac tissue through molecular reprogramming of the cardiac myocytes themselves. Thus these studies provide novel new insight into the cellular and molecular mechanisms that underlie the therapeutic benefit of hMSCs in the setting of heart failure. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

[Primary glucocorticoid resistance syndrome presenting as pseudo-precocious puberty and galactorrhea].

HISTORY AND CLINICAL FINDINGS: Primary glucocorticoid resistance syndrome (PGRS) is a rare condition characterized by hypercortisolism without Cushing's syndrome. This report describes a 7-year-old boy of PGRS with pseudo-precocious puberty and galactorrhea as the main manifestation. His height was 135 cm and body weight was 31 kg. Pigmentation could be seen in the skin, mammary areola and penis. He had hirsutism, low hair line, coarse voice, Tanner stage 3 pubic hair, penis in adult form, accelerated linear growth, and advanced bone age (13 yr.), but normal (for age) testes. Furthermore, he had mammoplasia and galactorrhea. There were no features of glucocorticoid (GC) excess. LABORATORY FINDINGS: Hepatic function was impaired (ALT 1426 IU/L, AST 611 IU/L) with no definite causes. Serum cortisol concentration was 1294 nmol/L, 777 nmol/L, 199.3 nmol/L at 8:00, 16:00 and 24:00 respectively. Plasma adrenocorticotropic hormone (ACTH) was normal or a little higher (43.9-80 ng/L). Urinary-free cortisol (UFC) was normal (55.5-62.4 microg/24 h). Serum estradiol (E2), progesterone (P), testosterone (T), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were normal. Serum dehydroepiandrosterone sulfate (DHEAS, 60 microg/dL) and serum prolactin (PRL, 58.7-183.9 ng/mL) level were high, urinary dehydroepiandrosterone (DHEA) level was also elevated (0.96-3.2 mg/mL). Gonadotrophin hormone-releasing hormone (GnRH) stimulation test was negative. Serum cortisol responded normally to insulin-induced hypoglycemia. However, serum cortisol and plasma ACTH concentration was suppressed to more than 50% by 0.5 mg dexamethasone (DEX). The diagnosis of PGRS was made. TREATMENT AND FOLLOW-UP: The patient received a treatment of 0.75-1.0 mg/d DEX. Because of galactorrhea, bromocriptine was given by 1.25-3.75 mg/d. After 24 months follow-up, the pigmentation was relieved and galactorrhea disappeared. No advanced development of the external genitalia and breast was found. The acceleration of the bone age was also slowed down. But he still had obvious hirsutism. No side effect of DEX was found. CONCLUSION: PGRS may present with pseudo-precocious puberty and galactorrhea. The aim of treatment in glucocorticoid resistance is to suppress the excessive secretion of ACTH and the increased production of adrenal androgens. The administration of synthetic GC with minimal intrinsic mineralocorticoid activity, such as DEX, provides a rational treatment for PGRS. Long-term DEX treatment should be individualized and carefully titrated based on the clinical manifestations and biochemical profile in order to control the clinical manifestations of the disease.

STIM2 is an inhibitor of STIM1-mediated store-operated Ca2+ Entry.

The coupling mechanism between endoplasmic reticulum (ER) Ca(2+) stores and plasma membrane (PM) store-operated channels (SOCs) remains elusive [1-3]. STIM1 was shown to play a crucial role in this coupling process [4-7]; however, the role of the closely related STIM2 protein remains undetermined. We reveal that STIM2 is a powerful SOC inhibitor when expressed in HEK293, PC12, A7r5, and Jurkat T cells. This contrasts with gain of SOC function in STIM1-expressing cells. While STIM1 is expressed in both the ER and plasma membrane, STIM2 is expressed only intracellularly. Store depletion induces redistribution of STIM1 into distinct "puncta." STIM2 translocates into puncta upon store depletion only when coexpressed with STIM1. Double labeling shows coincidence of STIM1 and STIM2 within puncta, and immunoprecipitation reveals direct interactions between STIM1 and STIM2. Independent of store depletion, STIM2 colocalizes with and blocks the function of a STIM1 EF-hand mutant that preexists in puncta and is constitutively coupled to activate SOCs. Thus, whereas STIM1 is a required mediator of SOC activation, STIM2 is a powerful inhibitor of this process, interfering with STIM1-mediated SOC activation at a point downstream of puncta formation. The opposing functions of STIM1 and STIM2 suggest they may play a coordinated role in controlling SOC-mediated Ca(2+) entry signals.

STIM1 has a plasma membrane role in the activation of store-operated Ca(2+) channels.

Receptor-induced Ca(2+) signals are key to the function of all cells and involve release of Ca(2+) from endoplasmic reticulum (ER) stores, triggering Ca(2+) entry through plasma membrane (PM) "store-operated channels" (SOCs). The identity of SOCs and their coupling to store depletion remain molecular and mechanistic mysteries. The single transmembrane-spanning Ca(2+)-binding protein, STIM1, is necessary in this coupling process and is proposed to function as an ER Ca(2+) sensor to provide the trigger for SOC activation. Here we reveal that, in addition to being an ER Ca(2+) sensor, STIM1 functions within the PM to control operation of the Ca(2+) entry channel itself. Increased expression levels of STIM1 correlate with a gain in function of Ca(2+) release-activated Ca(2+) (CRAC) channel activity. Point mutation of the N-terminal EF hand transforms the CRAC channel current (I(CRAC)) into a constitutively active, Ca(2+) store-independent mode. Mutants in the EF hand and cytoplasmic C terminus of STIM1 alter operational parameters of CRAC channels, including pharmacological profile and inactivation properties. Last, Ab externally applied to the STIM1 N-terminal EF hand blocks both I(CRAC) in hematopoietic cells and SOC-mediated Ca(2+) entry in HEK293 cells, revealing that STIM1 has an important functional presence within the PM. The results reveal that, in addition to being an ER Ca(2+) sensor, STIM1 functions within the PM to exert control over the operation of SOCs. As a cell surface signaling protein, STIM1 represents a key pharmacological target to control fundamental Ca(2+)-regulated processes including secretion, contraction, metabolism, cell division, and apoptosis.

Loperamide mobilizes intracellular Ca2+ stores in insulin-secreting HIT-T15 cells.

1 We have investigated the effects of loperamide on intracellular Ca(2+) stores and membrane K(+) channels in insulin-secreting hamster insulinoma (HIT-T15) cells. 2 In cell-attached patch-clamp mode, loperamide (3-250 micro M) activated large single-channel currents. The loperamide-activated currents were tentatively identified as Ca(2+)-activated K(+) channel (K(Ca)) currents based on their single-channel conductance (145 pS), apparent reversal potential, and insensitivity to tolbutamide. Smaller single-channel currents with a conductance (32 pS) indicative of adenosine triphosphate-sensitive K(+) channels (K(ATP) channels) were also recorded, but were insensitive to loperamide. 3 Surprisingly, the loperamide-activated currents persisted in the absence of extracellular Ca(2+). Yet under these conditions, we still measured loperamide-induced Ca(2+) increases. These effects are dose dependent. Loperamide had no effects in the inside-out patch configuration, suggesting that loperamide does not directly activate the channels with large conductance, but does so secondarily to release of Ca(2+) from intracellular stores. 4 Carbachol (100 micro M), an agonist of muscarinic receptors, which mediates IP(3)-dependent intracellular Ca(2+) release, enhanced the effects of loperamide on K(Ca) channels. 5 Both the putative K(Ca) currents and Ca(2+) signals induced by loperamide (with '0' [Ca(2+)](o)) were abolished when the intracellular Ca(2+) stores had been emptied by pretreating the cells with either carbachol or thapsigargin, an endoplasmic reticulum Ca(2+)-ATPase inhibitor that blocks reuptake of calcium. 6 These data indicate that loperamide in insulin-secreting beta-cells evokes intracellular Ca(2+) release from IP(3)-gated stores and activates membrane currents that appear to be carried by K(Ca), rather than K(ATP) channels.

Molecular determinants of cAMP-mediated regulation of the Na+-Ca2+ exchanger expressed in human cell lines.

The cardiac Na+-Ca2+ exchanger (NCX1) is one of the major sarcolemmal Ca2+ transporters of cardiomyocytes. Structure-function studies suggest that beta-adrenergic inhibition of NCX1, as reported for frog, but not mammalian hearts, may be associated with a unique splice variant of frog cardiac NCX1 where insertion of an extra exon completes the coding of a nucleotide binding P-loop. To test the involvement of the P-loop in cAMP-mediated regulation of NCX1 we used four stably transfected human cell lines (a previously established line of baby hamster kidney (BHK) cells and three new lines of human embryonic kidney (HEK) cells) expressing: (1) wild-type dog NCX1 (dog NCX1); (2) wild-type frog NCX1 (frog NCX1); (3) chimeric frog-dog NCX1 incorporating the completed P-loop from the frog NCX1 into the dog NCX1 sequence (frog/dog NCX1); and (4) a mutated frog NCX1 where a putative protein kinase A (PKA) site was disrupted by substitution of a single serine residue with glycine (S374G frog NCX1). Structural expression of these NCX1 constructs was confirmed using Western blot analysis of extracted proteins and immunofluorescence imaging. The NCX1-generated current (INa-Ca) was reliably measured in cells expressing dog (2.0 +/- 0.15 pA pF-1), frog (0.6 +/- 0.1 pA pF-1) and frog/dog (0.6 +/- 0.1 pA pF-1) NCX1, but less so in those expressing S374G frog NCX1 (0.3 +/- 0.1 pA pF-1). Addition of 100 microM 8-bromoadenosine 3',5' cyclic monophosphate (8-Br-cAMP) suppressed INa-Ca of frog and frog/dog NCX1 by 60-80 %. The suppression of INa-Ca was smaller and transient in cells expressing S374G frog NCX1, and absent in cells expressing dog NCX1. Intracellular Ca2+ (Ca2+i)-transients, activated by rapid withdrawal of Na+, were also downregulated in the frog and frog/dog NCX1 and to a smaller and transient extent in S374G frog NCX1. Our findings suggest that the suppressive effect of beta-adrenergic agonists requires the presence of the P-loop domain of the frog NCX1, and provide evidence that the putative PKA site, present in both dog and frog NCX1, might also be critical in the cAMP-mediated regulation of the exchanger.