THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: Ion channels

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15539. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Staging systems in bipolar disorder: an International Society for Bipolar Disorders Task Force Report

OBJECTIVE

We discuss the rationale behind staging systems described specifically for bipolar disorders. Current applications, future directions and research gaps in clinical staging models for bipolar disorders are outlined.

METHOD

We reviewed the literature pertaining to bipolar disorders, focusing on the first episode onwards. We systematically searched data on staging models for bipolar disorders and allied studies that could inform the concept of staging.

RESULTS

We report on several dimensions that are relevant to staging concepts in bipolar disorder. We consider whether staging offers a refinement to current diagnoses by reviewing clinical studies of treatment and functioning and the potential utility of neurocognitive, neuroimaging and peripheral biomarkers.

CONCLUSION

Most studies to date indicate that globally defined late-stage patients have a worse overall prognosis and poorer response to standard treatment, consistent with patterns for end-stage medical disorders. We believe it is possible at this juncture to speak broadly of 'early'- and 'late'-stage bipolar disorder. Next steps require further collaborative efforts to consider the details of preillness onset and intermediary stages, and how many additional stages are optimal.

Somatic rearrangement of T-cell antigen receptor gene in human T-cell malignancies

A cDNA clone representing the gene encoding the beta chain of the human T-cell antigen receptor has been isolated recently. By using fragments of this cDNA as hybridization probes in Southern blot analysis of restriction endonuclease-digested genomic DNA, we have now examined the structure of the gene in DNA from 26 patients with acute leukemia and from 23 normal individuals. We have found that the T-cell antigen receptor gene has undergone somatic rearrangement in 14 of 14 patients with the phenotypic diagnosis of T-cell acute lymphoblastic leukemia. In this group of patients, similar patterns of rearrangement appear to occur in different patients. This finding suggests that there is either a limited repertoire of possible rearrangements or an association between the development of leukemia and specific patterns of rearrangement. DNA from 6 patients with acute myeloblastic leukemia, 6 patients with non-B, non-T acute lymphoblastic leukemia, and 23 nonleukemic individuals showed no rearrangement or polymorphism. One case of T-cell acute lymphoblastic leukemia, however, showed rearrangement of both the T-cell receptor beta chain and the constant region of the immunoglobulin gene. Studies with mixtures of DNAs from leukemic bone marrow cells and cultured skin fibroblasts, as well as with remission and relapse marrow DNAs from the same patients, indicate that this technique can detect 1% leukemic cells in a mixed population. In addition, DNA from the marrow of a patient in relapse contains a similar rearrangement to that found in the marrow sample taken at the time of diagnosis, which suggests that the original clone of leukemic cells was responsible for relapse. Our results indicate that assessment of rearrangement of the T-cell antigen receptor gene will be valuable in the diagnosis and management of leukemia and can be used to evaluate clonality in T-cell neoplasia.

Predominant recurrence polarity among 928 adult international bipolar I disorder patients

OBJECTIVE

To test the hypothesis that patients with bipolar disorder (BPD) differ demographically and clinically within subgroups based on the predominant-polarity of major recurrences.

METHOD

We tested factors for association with predominantly (≥2 : 1) depressive vs. mania-like episodes with 928 DSM-IV type-I BPD subjects from five international sites.

RESULTS

Factors preliminarily associated with predominant-depression included: electroconvulsive treatment, longer latency-to-BPD diagnosis, first episode depressive or mixed, more suicide attempts, more Axis-II comorbidity, ever having mixed-states, ever married, and female sex. Predominant-mania was associated with: initial manic or psychotic episodes, more drug abuse, more education, and more family psychiatric history. Of the 47.3% of subjects without polarity-predominance, risks for all factors considered were intermediate. Expanding the definition of polarity-predominance to ≥51% added little, but shifting mixed-states to 'predominant-depression' increased risk of suicidal acts from 2.4- to 4.5-fold excess over predominant-mania-hypomania, and suicidal risk was associated continuously with increasing proportions of depressive or mixed episodes.

CONCLUSION

Subtyping by predominant-polarity yielded predictive associations, including the polarity of first episodes and risk of suicide attempts. Such subtyping may contribute to improve planning of clinical care and to biological studies of BPD.

Inducible azole resistance associated with a heterogeneous phenotype in Candida albicans

The development of azole resistance in Candida albicans is most problematic in patients with AIDS who receive long courses of drug for therapy or prevention of oral candidiasis. Recently, the rapid development of resistance was noted in other immunosuppressed patients who developed disseminated candidiasis despite fluconazole prophylaxis. One of these series of C. albicans isolates became resistant, with an associated increase in mRNA specific for a CDR ATP-binding cassette transporter efflux pump (K. A. Marr, C. N. Lyons, T. R. Rustad, R. A. Bowden, and T. C. White, Antimicrob. Agents Chemother. 42:2584-2589, 1998). Here we study this series of C. albicans isolates further and examine the mechanism of azole resistance in a second series of C. albicans isolates that caused disseminated infection in a recipient of bone marrow transplantation. The susceptible isolates in both series become resistant to fluconazole after serial growth in the presence of drug, while the resistant isolates in both series become susceptible after serial transfer in the absence of drug. Population analysis of the inducible, transiently resistant isolates reveals a heterogeneous population of fluconazole-susceptible and -resistant cells. We conclude that the rapid development of azole resistance occurs by a mechanism that involves selection of a resistant clone from a heterogeneous population of cells.

Increased TRPC5 glutathionylation contributes to striatal neuron loss in Huntington's disease

Aberrant glutathione or Ca(2+) homeostasis due to oxidative stress is associated with the pathogenesis of neurodegenerative disorders. The Ca(2+)-permeable transient receptor potential cation (TRPC) channel is predominantly expressed in the brain, which is sensitive to oxidative stress. However, the role of the TRPC channel in neurodegeneration is not known. Here, we report a mechanism of TRPC5 activation by oxidants and the effect of glutathionylated TRPC5 on striatal neurons in Huntington's disease. Intracellular oxidized glutathione leads to TRPC5 activation via TRPC5 S-glutathionylation at Cys176/Cys178 residues. The oxidized glutathione-activated TRPC5-like current results in a sustained increase in cytosolic Ca(2+), activated calmodulin-dependent protein kinase and the calpain-caspase pathway, ultimately inducing striatal neuronal cell death. We observed an abnormal glutathione pool indicative of an oxidized state in the striatum of Huntington's disease transgenic (YAC128) mice. Increased levels of endogenous TRPC5 S-glutathionylation were observed in the striatum in both transgenic mice and patients with Huntington's disease. Both knockdown and inhibition of TRPC5 significantly attenuated oxidation-induced striatal neuronal cell death. Moreover, a TRPC5 blocker improved rearing behaviour in Huntington's disease transgenic mice and motor behavioural symptoms in littermate control mice by increasing striatal neuron survival. Notably, low levels of TRPC1 increased the formation of TRPC5 homotetramer, a highly Ca(2+)-permeable channel, and stimulated Ca(2+)-dependent apoptosis in Huntington's disease cells (STHdh(Q111/111)). Taken together, these novel findings indicate that increased TRPC5 S-glutathionylation by oxidative stress and decreased TRPC1 expression contribute to neuronal damage in the striatum and may underlie neurodegeneration in Huntington's disease.

The Concise Guide to PHARMACOLOGY 2023/24: Ion channels

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16178. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Immunoglobulin mu-chain gene rearrangement in a patient with T cell acute lymphoblastic leukemia

A 6-yr-old girl with T cell acute lymphoblastic leukemia (ALL) is described. She had a mediastinal mass and her leukemic cells expressed T cell-associated antigens (Leu 1+, OKT3+, OKT9+, and OKT10+). When we examined genomic DNA from the leukemic cells, we detected Ig mu-chain gene rearrangement with germ-line configuration of light chain genes. As reported recently, detecting Ig gene rearrangement has become an important procedure for further classifying B cell precursor cells. This case, however, suggests that there is also heterogeneity among patients with T cell ALL, not only at the level of cell surface phenotypes, but also at the level of the Ig gene. These findings have major implications when we consider both the ontogenesis of these leukemic cells and the normal differentiation of human lymphocytes.

The heteromeric PC-1/PC-2 polycystin complex is activated by the PC-1 N-terminus

Mutations in the polycystin proteins, PC-1 and PC-2, result in autosomal dominant polycystic kidney disease (ADPKD) and ultimately renal failure. PC-1 and PC-2 enrich on primary cilia, where they are thought to form a heteromeric ion channel complex. However, a functional understanding of the putative PC-1/PC-2 polycystin complex is lacking due to technical hurdles in reliably measuring its activity. Here we successfully reconstitute the PC-1/PC-2 complex in the plasma membrane of mammalian cells and show that it functions as an outwardly rectifying channel. Using both reconstituted and ciliary polycystin channels, we further show that a soluble fragment generated from the N-terminal extracellular domain of PC-1 functions as an intrinsic agonist that is necessary and sufficient for channel activation. We thus propose that autoproteolytic cleavage of the N-terminus of PC-1, a hotspot for ADPKD mutations, produces a soluble ligand in vivo. These findings establish a mechanistic framework for understanding the role of PC-1/PC-2 heteromers in ADPKD and suggest new therapeutic strategies that would expand upon the limited symptomatic treatments currently available for this progressive, terminal disease.

On the surface of most animal and other eukaryotic cells are small rod-like protrusions known as primary cilia. Each cilium is encased by a specialized membrane which is enriched in protein complexes that help the cell sense its local environment. Some of these complexes help transport ions in out of the cell, while others act as receptors that receive chemical signals called ligands. A unique ion channel known as the polycystin complex is able to perform both of these roles as it contains a receptor called PC-1 in addition to an ion channel called PC-2.

Various mutations in the genes that code for PC-1 and PC-2 can result in autosomal dominant polycystic kidney disease (ADPKD), which is the most common monogenetic disease in humans. However, due to the small size of primary cilia – which are less than a thousandth of a millimeter thick – little is known about how polycystin complexes are regulated and how mutations lead to ADPKD. To overcome this barrier, Ha et al. modified kidney cells grown in the lab so that PC-1 and PC-2 form a working channel in the plasma membrane which surrounds the entire cell. As the body of a cell is around 10,000 times bigger than the cilium, this allowed the movement of ions across the polycystin complex to be studied using conventional techniques.

Experiments using this newly developed assay revealed that a region at one of the ends of the PC-1 protein, named the C-type lectin domain, is essential for stimulating polycystin complexes. Ha et al. found that this domain of PC-1 is able to cut itself from the protein complex. Further experiments showed that when fragments of PC-1, which contain the C-type lectin domain, are no longer bound to the membrane, they can activate the polycystin channels in cilia as well as the plasma membrane. This suggests that this region of PC-1 may also act as a secreted ligand that can activate other polycystin channels.

Some of the genetic mutations that cause ADPKD likely disrupt the activity of the polycystin complex and reduce its ability to transport ions across the cilia membrane. Therefore, the cell assay created in this study could be used to screen for small molecules that can restore the activity of these ion channels in patients with ADPKD.

Regulation of calcium influx and signaling pathway in cancer cells via TRPV6-Numb1 interaction

Ca(2+) is a critical factor in the regulation of signal transduction and Ca(2+) homeostasis is altered in different human diseases. The level of Ca(2+) in cells is highly regulated through a diverse class of regulators. Among them is the transient receptor potential vanilloid 6 (TRPV6), which is a Ca(2+) selective channel that absorbs Ca(2+) in the small intestine. TRPV6 is overexpressed in some cancers and exhibits oncogenic potential, but its exact mechanism is still poorly understood. The Numb protein is a cell fate determinant that functions in endocytosis and as a tumor suppressor via the stabilization of p53. Numb protein consisted of four isoforms. Here, we showed a novel function of Numb1, which negatively regulates TRPV6 activity. The expression of Numb1 decreased cytosolic Ca(2+) concentrations in TRPV6-transfected HEK293 cells. When all the isoforms of Numb were depleted using siRNA in a TRPV6 stable cell line, the levels of cytosolic Ca(2+) increased. We observed an interaction between Numb1 and TRPV6 using co-immunoprecipitation. We confirmed this interaction using Fluorescence Resolution Energy Transfer (FRET). We identified the TRPV6 and Numb1 binding site using TRPV6 C-terminal truncation mutants and Numb1 deletion mutants. The binding site in TRPV6 was an aspartic acid at amino acid residue 716, and that binding site in Numb1 was arginine at amino acid residue 434. A Numb1 mutant, lacking TRPV6 binding activity, failed to inhibit TRPV6 activity. Every isoform of Numb knockdown, using an siRNA-based approach in MCF-7 breast cancer cells, not only showed enhanced TRPV6 expression but also both the cytosolic Ca(2+) concentration and cell proliferation were increased. The down-regulated expression of TRPV6 using siRNA increased Numb protein expression; however, the cytosolic influx of Ca(2+) and proliferation of the cell were decreased. To examine downstream signaling during Ca(2+) influx, we performed Western blotting analysis on TRPV6 upregulated cancer cells (MCF-7, PC-3). Taken together, these results demonstrated that Numb1 interacts with TRPV6 through charged residues and inhibits its activity via the regulation of protein expression. Moreover, we provided evidence for a Ca(2+)-regulated cancer cell signaling pathway and that the Ca(2+) channel is a target of cancer cells.

Lineage specific classification of leukaemia: results of the analysis of sixty cases of childhood leukaemia

In addition to conventional morphological, histochemical and immunological marker studies, cells from 60 children with leukaemia were further analysed using the Southern blot hybridization technique to look at differences in the organization of immunoglobulin (Ig) genes. Of the 60 patients studied by conventional means, 47 were diagnosed as acute lymphocytic leukaemia (ALL) and 13 as non-lymphocytic leukaemia. Seven patients were initially classified as T ALL and 40 as non-T, non-B ALL. Further subclassification of the 40 patients with non-T, non-B ALL indicated three pre-B ALL and 29 patients diagnosed as common ALL, expressing Ia and CALLA antigens. All 29 patients with common ALL demonstrated C mu gene rearrangements with or without light chain (kappa and lambda) genes rearrangement. Based on the developmental hierarchy of Ig gene rearrangement, it was possible to further subclassify the patients with common ALL into different stages of B cell development. Eight (of the 40) patients with non-T, non-B ALL were identified as CALLA- but further analysis indicated T-lineage origin in two patients and three patients were reclassified as acute undifferentiated leukaemia (AUL). C mu gene rearrangements were detected in two patients with T ALL, two patients with AUL and one patient with acute myelogenous leukaemia (AML). In contrast to the patients with common ALL, Ig gene rearrangement observed in these non-B-lineage cells was restricted to a single C mu gene while retaining germ-line configuration of the other allele of the C mu gene and both light chain genes.

Dual action of the Gαq-PLCβ-PI(4,5)P2 pathway on TRPC1/4 and TRPC1/5 heterotetramers

The transient receptor potential canonical (TRPC) 1 channel is widely distributed in mammalian cells and is involved in many physiological processes. TRPC1 is primarily considered a regulatory subunit that forms heterotetrameric channels with either TRPC4 or TRPC5 subunits. Here, we suggest that the regulation of TRPC1/4 and TRPC1/5 heterotetrameric channels by the Gα_q-PLCβ pathway is self-limited and dynamically mediated by Gα_q and PI(4,5)P₂. We provide evidence indicating that Gα_q protein directly interacts with either TRPC4 or TRPC5 of the heterotetrameric channels to permit activation. Simultaneously, Gα_q-coupled PLCβ activation leads to the breakdown of PI(4,5)P₂, which inhibits activity of TRPC1/4 and 1/5 channels.

Extracellular disulfide bridges stabilize TRPC5 dimerization, trafficking, and activity

Crucial cysteine residues can be involved in the modulation of protein activity via the modification of thiol (-SH) groups. Among these reactions, disulfide bonds (S-S) play a key role in the folding, stability, and activity of membrane proteins. However, the regulation of extracellular cysteines in classical transient receptor potential (TRPC) channels remains controversial. Here, we examine the functional importance of the extracellular disulfide bond in TRPC5 in modulating channel gating and trafficking. Specifically, we investigated TRPC5 activity in transiently transfected HEK293 cells with wild-type (WT) or cysteine (C553 and C558) mutants in the pore loop. Using reducing agents, we determined that a disulfide linkage mediates the tetrameric formation of the TRPC5 channel. By measuring the TRPC5 current, we observed that C553S or C558S mutants completely lose channel activity induced by lanthanides or receptor stimulation. Co-expression of TRPC5 (WT) with mutants demonstrated a dominant-negative function in mutants, which inhibited the activity of TRPC5 (WT). We generated TRPC5-TRPC5 dimers and observed reduced activity of WT-mutant (C553S or C558S) dimers compared to WT-WT dimers. When pretreated with reducing agents for 12 h, the TRPC5 current decreased due to a reduction in membrane TRPC5 distribution. In addition, we identified a reduced expression of C553S mutant in plasma membrane. We analyzed a dimeric interaction of wild-type and mutant TRPC5 using co-immunoprecipitation and FRET method, indicating a weak interaction between dimeric partners. These results indicated that the disulfide bond between conserved extracellular cysteines, especially C553, is essential for functional TRPC5 activity by channel multimerization and trafficking.

Islet amyloid inhibitors improve glucose homeostasis in a transgenic mouse model of type 2 diabetes

Increasing evidence points to the cytotoxicity of islet amyloid polypeptide (IAPP) aggregates as a major contributor to the loss of β-cell mass in type 2 diabetes. Prevention of IAPP formation represents a potential treatment to increase β-cell survival and function. The IAPP inhibitory peptide, D-ANFLVH, has been previously shown to prevent islet amyloid accumulation in cultured human islets. To assess its activity in vivo, D-ANFLVH was administered by intraperitoneal injection into a human IAPP transgenic mouse model, which replicates type 2 diabetes islet amyloid pathology. The peptide was a potent inhibitor of islet amyloid deposition, resulting in reduced islet cell apoptosis and preservation of β-cell area leading to improved glucose tolerance. These findings provide support for a key role of islet amyloid in β-cell survival and validate the application of anti-amyloid compounds as therapeutic strategies to maintain normal insulin secretion in patients with type 2 diabetes.

Low-carbohydrate diet and the risk of metabolic syndrome in Korean adults

BACKGROUND & AIMS

The association of low-carbohydrate diet with weight loss and the risk of cardiovascular diseases has recently been the focus of increasing research attention. However, studies on low-carbohydrate diet in the Asian population are limited. The present study was aimed to examine the association between low-carbohydrate diet and metabolic syndrome among Korean adults.

METHODS AND RESULTS

A total of 16,349 participants aged 30 years or older who participated in a 24-h dietary recall survey of the fifth and sixth Korea National Health and Nutrition Examination Survey were included in this study. Low-carbohydrate diet was evaluated using the low-carbohydrate-diet score, which was calculated based on the percentage of energy from carbohydrate, protein, and fat by sex. The association between the low-carbohydrate-diet score and metabolic syndrome was analyzed using multiple logistic regression analysis. A low-carbohydrate diet was not associated with metabolic syndrome and its components such as waist circumference, blood pressure, and triglyceride levels. However, women in the highest decile of the animal- or plant-based low-carbohydrate-diet score showed a decreased risk of reduced high-density lipoprotein (HDL)-cholesterol levels, and men in the highest decile of the animal-based low-carbohydrate-diet score showed a decreased risk of reduced HDL-cholesterol levels than those in the lowest decile of the low-carbohydrate-diet score.

CONCLUSION

These findings indicate that, in Korea, a low-carbohydrate diet did not increase the risk of metabolic syndrome among adults who typically consume a high-carbohydrate low-fat diet. However, it may moderately decrease the risk of reduced HDL-cholesterol levels.

Single-mode optical waveguides

An efficient and powerful technique has been developed to treat the problem of wave propagation along arbitrarily shaped single-mode dielectric waveguides with inhomogeneous index variations in the cross-sectional plane. This technique is based on a modified finite-element method. Illustrative examples were given for the following guides: (a) the triangular fiber guide; (b) the elliptical fiber guide; (c) the single material fiber guide; (d) the rectangular fiber guide; guide; (g) the optical stripline guide.

Gs cascade regulates canonical transient receptor potential 5 (TRPC5) through cAMP mediated intracellular Ca2+ release and ion channel trafficking

Canonical transient receptor potential (TRPC) channels are Ca(2+)-permeable, non-selective cation channels those are widely expressed in mammalian cells. Various molecules have been found to regulate TRPC both in vivo and in vitro, but it is unclear how heterotrimeric G proteins transmit external stimuli to regulate the activity of TRPC5. Here, we demonstrated that TRPC5 was potentiated by the Gα(s) regulatory pathway. Whole-cell TRPC5 current was significantly increased by β-adrenergic receptor agonist, isoproterenol (ISO, 246±36%, n=6), an activator of the adenylate cyclase, forskolin (FSK, 273±6%, n=5), or a membrane permeable cAMP analogue, 8-Br-cAMP (251±63%, n=7). In addition, robust Ca(2+) transient induced by isoproterenol was observed utilizing a Ca(2+) imaging technique. When intracellular [Ca(2+)](i) was buffered to 50nM, cAMP-induced potentiation was attenuated. We also found that the Ca(2+) release is mediated by IP(3) since intracellular IP(3) infusion attenuated the potentiation of TRPC5 by Gα(s) cascade. Finally, we identified that the membrane localization of TRPC5 was significantly increased by ISO (155±17%, n=3), FSK (172±39%, n=3) or 8-Br-cAMP (216±59%, n=3). In conclusion, these results suggest that the Gα(s)-cAMP pathway potentiates the activity of TRPC5 via facilitating intracellular Ca(2+) dynamics and increasing channel trafficking to the plasma membrane.

Mathematical Model-Based Accelerated Development of Extended-release Metformin Hydrochloride Tablet Formulation

A computational fluid dynamic (CFD) model was developed to predict metformin release from a hydroxypropylmethylcellulose (HPMC) matrix-based extended-release formulation that took into consideration the physical and chemical properties of the drug substance, composition, as well as size and shape of the tablet. New high dose strength (1000 mg) tablet geometry was selected based on the surface area/volume (SA/V) approach advocated by Lapidus/Lordi/Reynold to obtain the desired equivalent metformin release kinetics. Maintaining a similar SA/V ratio across all extended-release metformin hydrochloride (Met XR) tablet strengths that had different geometries provided similar simulations of dissolution behavior. Experimental dissolution profiles of three lots of high-strength tablets agreed with the simulated release kinetics. Additionally, a pharmacokinetic absorption model was developed using GastroPlus™ software and known physicochemical, pharmacokinetic, and in vitro dissolution properties of metformin to predict the clinical exposure of the new high strength (1000 mg) tablet prior to conducting a human clinical bioequivalence study. In vitro metformin release kinetics were utilized in the absorption model to predict exposures in humans for new 1000-mg Met XR tablets, and the absorption model correctly projected equivalent in vivo exposure across all dose strengths. A clinical bioequivalence study was pursued based on the combined modeling results and demonstrated equivalent exposure as predicted by the simulations.

Reciprocal positive regulation between TRPV6 and NUMB in PTEN-deficient prostate cancer cells

Calcium acts as a second messenger and plays a crucial role in signaling pathways involved in cell proliferation. Recently, calcium channels related to calcium influx into the cytosol of epithelial cells have attracted attention as a cancer therapy target. Of these calcium channels, TRPV6 is overexpressed in prostate cancer and is considered an important molecule in the process of metastasis. However, its exact role and mechanism is unclear. NUMB, well-known tumor suppressor gene, is a novel interacting partner of TRPV6. We show that NUMB and TRPV6 have a reciprocal positive regulatory relationship in PC-3 cells. We repeated this experiment in two other prostate cancer cell lines, DU145 and LNCaP. Interestingly, there were no significant changes in TRPV6 expression following NUMB knockdown in DU145. We revealed that the presence or absence of PTEN was the cause of NUMB-TRPV6 function. Loss of PTEN caused a positive correlation of TRPV6-NUMB expression. Collectively, we determined that PTEN is a novel interacting partner of TRPV6 and NUMB. These results demonstrated a novel relationship of NUMB-TRPV6 in prostate cancer cells, and show that PTEN is a novel regulator of this complex.

Single allelic C mu gene rearrangements in patients with T cell and undifferentiated leukemia

By using a panel of monoclonal antibodies in combination with conventional morphological and histochemical studies, seven leukemic patients were diagnosed as having T-cell lymphocytic leukemia (ALL) and three patients were classified as having acute undifferentiated leukemia (AUL). When genomic DNA from each patient was analysed by the Southern blot hybridization technique, two out of seven cases with T-cell ALL and two of three cases with AUL demonstrated immunoglobulin (Ig) mu gene rearrangements. Interestingly, the patterns of C mu gene rearrangement found in these four cases as well as in the T-cell line HSB-2 were quite similar with rearrangement of a single allele and germ line configuration retained in the other allele. Ig gene rearrangement is an essential property of cells of B-lineage, but detection of an Ig gene rearrangement by itself seems insufficient to assign commitment to B-lineage differentiation. The significance of Ig gene rearrangements in T-cell ALL is unclear, but this heterogeneity at the DNA level among T-cell ALL may reflect differences in leukemogeneis and have prognostic and therapeutic implications.

Volume regulation in lymphoid leukemia cells and assignment of cell lineage

Normal T lymphocytes readjust their volume after swelling in hypotonic medium, whereas B lymphocytes remain swollen. The difference between the two cell types appears to lie in the inability of B cells to increase their permeability to potassium in response to swelling. We have studied mononuclear cells from the bone marrow of 65 patients with lymphocytic leukemia, to determine whether the response to a hypotonic environment could be used to assign cell lineage. In contrast to leukemic cells of B-cell lineage (as in B-cell acute or chronic lymphocytic leukemia and non-T-cell, non-B-cell acute lymphocytic leukemia), T-cell-leukemia cells responded within five minutes to hypotonic swelling with an increase in potassium permeability and restoration toward isotonic volume. We conclude that the response to hypotonic shock may distinguish leukemic cells of T-cell origin from those derived from B-cell precursors and provides a simple, rapid, and reliable means for assigning cell lineage to lymphoid leukemia cells.

Electrophysiological characteristics of six mutations in hClC-1 of Korean patients with myotonia congenita

ClC-1 is a member of a large family of voltage-gated chloride channels, abundantly expressed in human skeletal muscle. Mutations in ClC-1 are associated with myotonia congenita (MC) and result in loss of regulation of membrane excitability in skeletal muscle. We studied the electrophysiological characteristics of six mutants found among Korean MC patients, using patch clamp methods in HEK293 cells. Here, we found that the autosomal dominant mutants S189C and P480S displayed reduced chloride conductances compared to WT. Autosomal recessive mutant M128I did not show a typical rapid deactivation of Cl(-) currents. While sporadic mutant G523D displayed sustained activation of Cl(-) currents in the whole cell traces, the other sporadic mutants, M373L and M609K, demonstrated rapid deactivations. V1/2 of these mutants was shifted to more depolarizing potentials. In order to identify potential effects on gating processes, slow and fast gating was analyzed for each mutant. We show that slow gating of the mutants tends to be shifted toward more positive potentials in comparison to WT. Collectively, these six mutants found among Korean patients demonstrated modifications of channel gating behaviors and reduced chloride conductances that likely contribute to the physiologic changes of MC.

Phenotypic heterogeneity at the DNA level in childhood leukemia with a mediastinal mass

Although phenotypic heterogeneity of childhood T-cell acute lymphocytic leukemia (T-ALL) which bear receptors for sheep red blood cells (E-rosettes) and/or T-cell-associated antigens has been reported, there are certain clinical features which are shared by most patients. A mediastinal mass is one of the most characteristic presentations in this particular disorder. This report describes four children with ALL, who presented with a mediastinal mass. Three patients were E-rosette-negative and one was E-rosette-positive. Individual surface phenotypes, defined by a panel of monoclonal antibodies, were quite different. Since Ig gene organization is an essential property of cells of B-lineage, it was surprising to find that analysis of genomic DNA revealed immunoglobulin (Ig) gene rearrangements in two of them. These findings suggest that there is significant heterogeneity even among those leukemias associated with a mediastinal mass, and that a mediastinal mass may not clearly indicate origin from cells of T-lineage. This heterogeneity may reflect differences in leukemogenesis and may have prognostic and therapeutic implications.