Lung Cancer Wherein Durvalumab Induced Both Anti-CRMP-5 Antibody-related Paraneoplastic Neurological Syndromes and Neurological Adverse Events

A 68-year-old man with small-cell lung cancer developed anti-collapsin response-mediator protein (CRMP)-5 antibody-related paraneoplastic neurological syndrome (PNS) presenting with ataxia and chorea during treatment with durvalumab. As a result of steroid therapy, anti-CRMP-5 antibodies became negative, hyperintense lesions on brain magnetic resonance imaging disappeared, and neurological symptoms improved. After resuming durvalumab, he became unable to walk due to neurological adverse events (nAEs). There have been no reported cases manifesting PNSs and nAEs as a result of the same immune checkpoint inhibitors (ICIs) administered at different times. Resuming ICIs in patients diagnosed with PNSs should be performed with prudence.

Involvement of autoimmunity to REG, a regeneration factor, in patients with primary Sjögren's syndrome

The regenerating gene (Reg) was isolated originally as a gene specifically over-expressed in regenerating pancreatic islets and constitute a growth factor family. Reg gene product (Reg) is important in the pathophysiology of various human inflammatory diseases. Recently, the possible involvement of human REG in the regeneration of salivary ductal epithelial cells of patients with primary Sjögren's syndrome (SS) was reported. However, the expression of the REG family genes in minor salivary glands (MSG) and the occurrence of anti-REG Iα autoantibodies in SS patients were obscured. In this study, we examined the expression of REG family genes in the MSG of SS and screened anti-REG Iα autoantibodies in SS. The mRNA levels of REG family genes in MSG were quantified using real-time reverse transcription-polymerase chain reaction (RT-PCR) and REG Iα expression in the MSG was analysed by immunohistochemistry. The mRNA level of REG Iα in the MSG of SS patients was significantly higher than that of control. REG Iα protein was expressed highly in SS ductal epithelial cells. Anti-REG Iα autoantibodies in the sera were found in 11% of SS. All the MSG in the anti-REG Iα autoantibody-positive group showed REG Iα expression, whereas only 40% showed REG Iα expression in the anti-REG Iα autoantibody-negative group. The anti-REG Iα autoantibody-positive group showed significantly lower saliva secretion and a higher ratio of grade 4 (by Rubin-Holt) in sialography. These data suggest strongly that autoimmunity to REG Iα might play a role in the degeneration of MSG ductal epithelial cells in primary SS.

Deletion of platelet-derived growth factor receptor-β improves diabetic nephropathy in Ca²⁺/calmodulin-dependent protein kinase IIα (Thr286Asp) transgenic mice

AIMS/HYPOTHESIS

The activation of platelet-derived growth factor receptor-β (PDGFR-β) signalling is increased in the glomeruli and tubules of diabetic animals. In this study, we examined the role of PDGFR-β signalling during the development of diabetic nephropathy.

METHODS

We recently generated pancreatic beta cell-specific Ca(2+)/calmodulin-dependent protein kinase IIα (Thr286Asp) transgenic mice (CaMKIIα mice), which show very high plasma glucose levels up to 55.5 mmol/l and exhibit the features of diabetic nephropathy. These mice were crossed with conditional knockout mice in which Pdgfr-β (also known as Pdgfrb) was deleted postnatally. The effect of the deletion of the Pdgfr-β gene on diabetic nephropathy in CaMKIIα mice was evaluated at 10 and 16 weeks of age.

RESULTS

The plasma glucose concentrations and HbA(1c) levels were elevated in the CaMKIIα mice from 4 weeks of age. Variables indicative of diabetic nephropathy, such as an increased urinary albumin/creatinine ratio, kidney weight/body weight ratio and mesangial area/glomerular area ratio, were observed at 16 weeks of age. The postnatal deletion of the Pdgfr-β gene significantly decreased the urinary albumin/creatinine ratio and mesangial area/glomerular area ratio without affecting the plasma glucose concentration. Furthermore, the increased oxidative stress in the kidneys of the CaMKIIα mice as shown by the increased urinary 8-hydroxydeoxyguanosine (8-OHdG) excretion and the increased expression of NAD(P)H oxidase 4 (NOX4), glutathione peroxidase 1 (GPX1) and manganese superoxide dismutase (MnSOD) was decreased by Pdgfr-β gene deletion.

CONCLUSIONS/INTERPRETATION

The activation of PDGFR-β signalling contributes to the progress of diabetic nephropathy, with an increase in oxidative stress and mesangial expansion in CaMKIIα mice.

Regenerating gene 1α (REG 1α) expression and new treatment strategies in early non-small cell lung cancer

e22178

Background: Regenerating gene (REG) I was originally isolated as an endogenous growth factor from pancreatic islet β cells. REG Iα protein is suggested to be involved in carcinogenesis in various gastroenterologic tissues. In the present study, to elucidate roles for REG Iα in non-small cell lung cancer (NSCLC), we investigated REG Iα expression in NSCLCs, focusing especially on its relationship with prognosis. Methods: We enrolled 70 NSCLCs (adenocarcinoma (AC)(n=48) and squamous cell carcinoma (SCC)(n=22)) who received surgery at Nara Medical University Hospital. Total RNA was extracted from each tumor tissue and corresponding normal lung tissue (NL)(n=70), cDNA was then reverse-transcribed from total RNA, and quantitative real-time reverse transcriptase-polymerase chain reaction was then carried out. The expression level of REG Iα in each sample was normalized with respect to that of β-actin, and the cutoff level was set at average+3SD expression of the 70 NLs. We also examined the relationship between REG 1α expression in the tumor tissue and the prognosis. Results: Six (12.5%) of the 48 ACs and 5 (22.7%) of the 22 SCCs were positive for REG Iα gene, and which is higher than that of NLs (2 of 70: 2.9%). After median follow-up of 26.2 months, 12 patients died due to disease progression. The survival rate among the REG 1α positive patients was significantly worse than among the REG 1α negative patients in ACs (P<0.05), and not significantly but worse in SCCs (P=0.07). In case of stage I, none of REG 1α negative patient died in both ACs and SCCs compared with 4 patients died of positive patients (AC:2, SCC:2), and also the survival rate among the REG 1α positive patients was significantly worse than among the negative patients in ACs (P<0.01) and SCCs (P<0.05). Disease free survival of REG 1α positive patients was also worse than negative patients in ACs (P<0.05) and SCCs (P=0.16). Conclusions: REG Iα expression in NSCLCs may be the risk factor for poor prognosis, and we anticipate that it will enable us to provide more appropriate and individualized treatment to patients of early NSCLC.

No significant financial relationships to disclose.

Reg (regenerating) gene overexpression in islets from non-obese diabetic mice with accelerated diabetes: role of IFNbeta

AIMS/HYPOTHESIS

The expression of IFNbeta in beta cells results in accelerated type 1 diabetes. The REG family of beta cell proliferation factors have been described as autoantigens in autoimmune diabetes. The aim of this study was to determine the effect of IFNbeta on Reg expression, and the implications of this in terms of autoimmunity.

METHODS

Reg gene expression was determined in islets from non-obese diabetic (NOD) RIP-HuIFNbeta mice by cDNA microarray, quantitative real-time PCR and immunohistochemistry. The effect of IFNbeta on Reg1 and Reg2 expression was assessed in the NOD insulinoma cell line NIT-1. IL-6, known to induce Reg expression, was measured in the insulitis microenvironment. Morphological studies were carried out to determine islet enlargement in this model.

RESULTS

Reg2 was upregulated in islets from the NOD RIP-HuIFNbeta mice at the onset of the autoimmune attack. IFNbeta upregulates Reg1 and Reg2 genes in NIT-1 cells. The expression of Il6 was increased in islets from transgenic mice and in NIT-1 cells exposed to HuIFNbeta. Moreover, islets from transgenic mice were enlarged compared with those from wild-type mice.

CONCLUSIONS/INTERPRETATION

Reg overexpression correlates well with the acceleration of diabetes in this model. The upregulation of Reg suggests that islets try to improve hyperglycaemia by regenerating the cells lost in the autoimmune attack. Reg expression is regulated by several factors such as inflammation. Therefore, the overexpression of an IFNbeta-induced autoantigen (REG) in the islets during inflammation might contribute to the premature onset of diabetes.

Reg I-knockout mice reveal its role in regulation of cell growth that is required in generation and maintenance of the villous structure of small intestine

Reg I (regenerating gene product I) is a growth factor that plays a central role in the generation and regeneration of the gastric mucosal architecture. On the other hand, mouse Reg I mRNA is expressed at the highest levels in the small intestine among the gastrointestinal tissues. In the current study, with the aim to clarify the role of Reg I protein in the small intestine, the temporal and spatial pattern of Reg I expression and the phenotype of Reg I-knockout mice in the tissue were examined. In the wild-type mice, immunohistochemistry localized Reg I protein expression in absorptive cells located in the lower half of the intestinal villi. Reg I expression was undetectable until embryonic day 13 (E13), when the fetal intestine still lacks villous structure; however, it dramatically increased at E17 along with the formation and maturation of the fetal intestinal villi. In the small intestine of the adult Reg I-knockout mice, less densely packed, round-shaped aberrant morphology of the absorptive cells was observed light microscopically, and electron microscopical examination revealed a strikingly loose connection of these cells to the basement membrane. Antiproliferating cell nuclear antigen staining and anti-Ki67 staining demonstrated the marked decrease in the number of proliferating cells in the small intestinal mucosa of the knockout mice. The cell migration speed visualized by one shot labeling of 5-bromodeoxyuridine was significantly slower in the knockout mice. These phenotypes of Reg I-knockout mice emerged, in accordance with the temporal pattern of Reg I expression described above, from E17. Reg I was considered to be a regulator of cell growth that is required to generate and maintain the villous structure of the small intestine.

Autoantibodies to REG, a beta-cell regeneration factor, in diabetic patients

BACKGROUND

Regenerating gene (Reg) product, Reg, acts as an autocrine/paracrine growth factor for beta-cell regeneration. The presence of autoimmunity against REG may affect the operative of the regenerative mechanisms in beta cells of Type 1 and Type 2 diabetes patients. We screened sera from Type 1 and Type 2 diabetes subjects for anti-REG autoantibodies, searched for correlations in the general characteristics of the subjects with the presence of anti-REG autoimmunity, and tested the attenuation of REG-induced beta-cell proliferation by the autoanitibodies.

MATERIAL AND METHODS

We examined the occurrence of anti-REG autoantibodies in patients' sera (265 Type 1, 368 Type 2 diabetes patients, and 75 unrelated control subjects) by Western blot analysis, and evaluated inhibitory effects of the sera on REG-stimulated beta-cell proliferation by a 5'-Bromo-2'-deoxyuridine (BrdU) incorporation assay in vitro.

RESULTS

Anti-REG autoantibodies were found in 24.9% of Type 1, 14.9% of Type 2 and 2.7% of control subjects (P = 0.0004). There were significant differences between the autoantibody positive and negative groups in the duration of disease in the Type 1 subjects (P = 0.0035), and the age of onset in the Type 2 subjects (P = 0.0274). The patient sera containing anti-REG autoantibodies significantly attenuated the BrdU incorporation by REG (35.6 +/- 4.06% of the control), whereas the nondiabetic sera without anti-REG autoantibodies scarcely reduced the incorporation (88.8 +/- 5.10%).

CONCLUSION

Anti-REG autoantibodies, which retard beta-cell proliferation in vitro, are found in some diabetic patients. Thus, autoimmunity to REG may be associated with the development/acceleration of diabetes in at least some patients.

Anti-CD38 autoimmunity in patients with chronic autoimmune thyroiditis or Graves' disease

Autoantibodies directed against human CD38 (an enzyme catalysing the interconversion of NAD(+) and cyclic ADP-ribose) have been demonstrated recently in patients with type 2 diabetes. We tested 220 consecutive Caucasian patients with autoimmune chronic thyroiditis, 104 patients with Graves' disease, 220 subjects from the general population (control I) and 78 healthy control subjects not affected by thyroid autoimmune disorders (control II) for the presence of anti-CD38 autoimmunity. Using Western blot analysis and optical densitometry, a specific band corresponding to human recombinant CD38 was identified in the serum of several subjects. By defining anti-CD38 positivity as a standardized optical reading > 3 s.d. higher than the mean value of control I, 10.4% of patients with thyroiditis and 7.7% of Graves' patients were anti-CD38 positive (P = 0.0009 versus 1.8% of control I). Similarly, 13.1% of patients with thyroiditis and 10.5% of Graves' patients had a standardized optical reading > 3 s.d. higher than the mean value of the subjects not affected by thyroid autoimmune disorders (P = 0.002 versus 1.2% of control II). Anti-CD38 autoimmunity did not differ between euthyroid, hyperthyroid or hypothyroid patients or between patients with or without thyroid hypoechogenicity. Anti-CD38 autoantibodies were associated with higher levels of circulating antithyroid-peroxidase antibodies (P = 0.03) and they were more frequent in Graves' patients with ophthalmopathy (P < 0.05). Anti-CD38 autoantibodies are a new autoimmune marker in chronic autoimmune thyroiditis and Graves' disease. The specific role of CD38 and its autoantibodies in the modulation of thyroid cell function or growth remains to be investigated.

Complete suppression of insulitis and diabetes in NOD mice lacking interferon regulatory factor-1

Interferon regulatory factor-1 (IRF-1), a transcriptional factor, regulates type I interferon and interferon-induced genes. It was reported that IRF-1 regulates important molecules required for inflammation and immune reactions. To investigate the role of IRF-1 in the development of autoimmune diabetes, we established IRF-1 deficient (IRF-1(-/-)) non-obese diabetic (NOD) mice. IRF-1-deficient C57BL/6J mice were out-crossed to NOD mice, and F1 were backcrossed to NOD mice. At the N8 generation, the heterozygote for IRF-1 mutation was intercrossed and N8F1 was obtained. Out of three NOD genotypes, IRF-1(+/+) and IRF-1(+/-) developed spontaneous diabetes with an incidence of 47% (9/19) and 50% (10/20) by 30 weeks of age, respectively; whereas IRF-1(-/-) did not develop diabetes (0/18, P< 0.01 vs. (+/+) and (+/-)). Histologically, IRF-1(+/+) and IRF-1(+/-) had various degrees of insulitis, but IRF-1(-/-) had no insulitis. In comparison with IRF-1(+/+), the percentage of CD4(+) and Mac-1(+) splenic cells significantly increased, whereas CD3(+), CD8(+) and B220(+) cells decreased in IRF-1(-/-). Furthermore, spleen cell proliferation in response to Con A or murine GAD65 peptide, a major autoantigen of the pancreatic beta-cell, significantly increased, and the IFN-gamma/IL-10 ratio in the culture supernatant significantly decreased in IRF-1(-/-), suggesting Th2 deviation in cytokine balance. These results indicate that IRF-1 plays a key role in developing insulitis and diabetes in NOD mice.

Development and prevention of advanced diabetic nephropathy in RAGE-overexpressing mice

Vascular complications arising from multiple environmental and genetic factors are responsible for many of the disabilities and short life expectancy associated with diabetes mellitus. Here we provide the first direct in vivo evidence that interactions between advanced glycation end products (AGEs; nonenzymatically glycosylated protein derivatives formed during prolonged hyperglycemic exposure) and their receptor, RAGE, lead to diabetic vascular derangement. We created transgenic mice that overexpress human RAGE in vascular cells and crossbred them with another transgenic line that develops insulin-dependent diabetes shortly after birth. The resultant double transgenic mice exhibited increased hemoglobin A(1c) and serum AGE levels, as did the diabetic controls. The double transgenic mice demonstrated enlargement of the kidney, glomerular hypertrophy, increased albuminuria, mesangial expansion, advanced glomerulosclerosis, and increased serum creatinine compared with diabetic littermates lacking the RAGE transgene. To our knowledge, the development of this double transgenic mouse provides the first animal model that exhibits the renal changes seen in humans. Furthermore, the phenotypes of advanced diabetic nephropathy were prevented by administering an AGE inhibitor, (+/-)-2-isopropylidenehydrazono-4-oxo-thiazolidin-5-ylacetanilide (OPB-9195), thus establishing the AGE-RAGE system as a promising target for overcoming this aspect of diabetic pathogenesis.

Transgenic CuZn-superoxide dismutase inhibits NO synthase induction in experimental subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The expression of inducible NO synthase (iNOS) after experimental subarachnoid hemorrhage (SAH) has been postulated to play a critical role in the pathogenesis of SAH and subsequent cerebral vasospasm. The inhibitory effect of CuZn-superoxide dismutase (CuZn-SOD) on the induction of iNOS after SAH was examined by using transgenic mice overexpressing CuZn-SOD.

METHODS

SOD-transgenic mice and nontransgenic littermates were subjected to SAH by endovascular perforation of the left anterior cerebral artery. The iNOS mRNA expression after SAH was determined by reverse transcription-polymerase chain reaction, and the distribution of iNOS-positive cells was immunohistochemically examined. The nuclear expression of activated nuclear factor-kappaB, a major transcription factor of iNOS gene, was also immunohistochemically examined.

RESULTS

In nontransgenic mice, SAH-induced iNOS protein and mRNA expressions in the arteries of basal cistern as well as in the cerebral cortex were demonstrated by immunohistochemistry and reverse transcription-polymerase chain reaction. SAH-induced iNOS protein and mRNA expressions in those tissues were much reduced in SOD-transgenic mice compared with nontransgenic mice. Moreover, the nuclear expression of the activated form of nuclear factor-kappaB was immunohistochemically detected in the cerebral cortices of nontransgenic mice but not in those of SOD-transgenic mice.

CONCLUSIONS

These results indicate that oxygen-derived free radicals, particularly superoxide, play an important role in the iNOS gene expression after SAH and provide a molecular basis for the protective role of SOD against vasospasm after SAH.

Human REG I gene is up-regulated in intrahepatic cholangiocarcinoma and its precursor lesions

The Reg I gene (regenerating gene) and its product (Reg protein) are a regenerating and/or proliferating factor(s) of pancreatic islet cells. The ectopic expression of REG Ialpha was shown in colorectal carcinomas, suggesting that REG Ialpha is related to their carcinogenesis. In this study, we examined the expression of REG I in intrahepatic cholangiocarcinoma (ICC) and its precursor lesion (biliary dysplasia). By polymerase chain reaction and in situ hybridization (ISH) studies using a total of 16 fresh liver specimens, REG Ialpha mRNA was demonstrated in 6 of 11 (55%) ICC cases, but in 0 of 5 (0%) normal livers. Immunohistochemistry for REG I protein was performed in 100 formalin-fixed, paraffin-embedded sections obtained from the 18 cases of ICC alone, 45 hepatolithiasis with ICC (n = 19) or biliary dysplasia (n = 26), 21 hepatolithiasis alone (all with hyperplasia), and 16 normal livers. In ICC, the expression of REG I protein was significantly dependent on the histologic differentiation; 12 of 13 (92%) cases in papillary and well-differentiated, 6 of 16 (38%) cases in moderately differentiated, and 0 of 8 (0%) cases in poorly differentiated types. Moreover, in the lesions of hyperplasia, low-grade dysplasia, and high-grade dysplasia in hepatolithiasis, REG I protein was expressed in 4 of 21 (19%), 7 of 12 (58%), and 13 of 14 (93%) cases, respectively. In normal liver, intrahepatic bile ducts were constantly negative for REG I protein. These findings suggest that neoexpression of REG I is a good marker for biliary mucosa at risk for development of ICC, and also that REG I plays a role in the early stages of biliary carcinogenesis, probably via a cell-proliferative effect.

Identification of cyclic ADP-ribose-dependent mechanisms in pancreatic muscarinic Ca(2+) signaling using CD38 knockout mice

We showed that muscarinic acetylcholine (ACh)-stimulation increased the cellular content of cADPR in the pancreatic acinar cells from normal mice but not in those from CD38 knockout mice. By monitoring ACh-evoked increases in the cytosolic Ca(2+) concentration ([Ca(2+)](i)) using fura-2 microfluorimetry, we distinguished and characterized the Ca(2+) release mechanisms responsive to cADPR. The Ca(2+) response from the cells of the knockout mice (KO cells) lacked two components of the muscarinic Ca(2+) release present in wild mice. The first component inducible by the low concentration of ACh contributed to regenerative Ca(2+) spikes. This component was abolished by ryanodine treatment in the normal cells and was severely impaired in KO cells, indicating that the low ACh-induced regenerative spike responses were caused by cADPR-dependent Ca(2+) release from a pool regulated by a class of ryanodine receptors. The second component inducible by the high concentration of ACh was involved in the phasic Ca(2+) response, and it was not abolished by ryanodine treatment. Overall, we conclude that muscarinic Ca(2+) signaling in pancreatic acinar cells involves a CD38-dependent pathway responsible for two cADPR-dependent Ca(2+) release mechanisms in which the one sensitive to ryanodine plays a crucial role for the generation of repetitive Ca(2+) spikes.

Activation of Reg gene, a gene for insulin-producing -cell regeneration: Poly(ADP-ribose) polymerase binds Reg promoter and regulates the transcription by autopoly(ADP-ribosyl)ation

The regeneration of pancreatic islet beta cells is important for the prevention and cure of diabetes mellitus. We have demonstrated that the administration of poly(ADP-ribose) synthetase/polymerase (PARP) inhibitors such as nicotinamide to 90% depancreatized rats induces islet regeneration. From the regenerating islet-derived cDNA library, we have isolated Reg (regenerating gene) and demonstrated that Reg protein induces beta-cell replication via the Reg receptor and ameliorates experimental diabetes. However, the mechanism by which Reg gene is activated in beta cells has been elusive. In this study, we found that the combined addition of IL-6 and dexamethasone induced the expression of Reg gene in beta cells and that PARP inhibitors enhanced the expression. Reporter gene assays revealed that the -81 approximately -70 region (TGCCCCTCCCAT) of the Reg gene promoter is a cis-element for the expression of Reg gene. Gel mobility shift assays showed that the active transcriptional DNA/protein complex was formed by the stimulation with IL-6 and dexamethasone. Surprisingly, PARP bound to the cis-element and was involved in the active transcriptional DNA/protein complex. The DNA/protein complex formation was inhibited depending on the autopoly(ADP-ribosyl)ation of PARP in the complex. Thus, PARP inhibitors enhance the DNA/protein complex formation for Reg gene transcription and stabilize the complex by inhibiting the autopoly(ADP-ribosyl)ation of PARP.

Neutrophil chemoattractant 2 beta regulates expression of the Reg gene in injured gastric mucosa in rats

BACKGROUND & AIMS

Regenerating (Reg) protein has a trophic effect on gastric mucosal cells. We have shown that Reg gene expression is increased in enterochromaffin-like (ECL) cells during the healing of damaged gastric mucosa around mucosal erosion. This study was designed to explore the stimulants of Reg expression during the healing of gastric mucosal damage.

METHODS

Time course changes of the expression of genes for various proinflammatory cytokines and Reg were investigated after induction of gastric mucosal lesions in rats. The direct effect of proinflammatory cytokines on Reg gene expression and Reg protein production were investigated in vitro using counterflow elutriation-enriched rat ECL cells. CXC receptor 2 (CXCR-2) expression was investigated in ECL cells by reverse-transcription polymerase chain reaction. Reg gene expression was also investigated in rats treated by the neutralizing antibody of cytokine-induced neutrophil chemoattractant (CINC-2 beta).

RESULTS

During healing, the gene expression of several proinflammatory cytokines and Reg was markedly augmented. Among the proinflammatory cytokines, CINC-2 beta is the only cytokine in which augmented expression preceded the increase of Reg gene expression. In rats treated with CINC-2 beta neutralizing antibody, the augmentation of Reg gene expression was significantly inhibited. When ECL cells were incubated with these proinflammatory cytokines, CINC-2 beta dose-dependently increased Reg messenger RNA and Reg protein in ECL cells. CXCR-2 was identified in isolated ECL cells.

CONCLUSIONS

CINC-2 beta, expressed in damaged gastric mucosa, stimulates the production of Reg protein in ECL cells via CXCR-2 and may be involved in the accelerated healing of injured gastric mucosa.

Altered stoichiometry of FKBP12.6 versus ryanodine receptor as a cause of abnormal Ca(2+) leak through ryanodine receptor in heart failure

BACKGROUND

In the pathogenesis of cardiac dysfunction in heart failure, a decrease in the activity of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase is believed to be a major determinant. Here, we report a novel mechanism of cardiac dysfunction revealed by assessing the functional interaction of FK506-binding protein (FKBP12.6) with the cardiac ryanodine receptor (RyR) in a canine model of pacing-induced heart failure.

METHODS AND RESULTS

SR vesicles were isolated from left ventricular muscles (normal and heart failure). The stoichiometry of FKBP12.6 per RyR was significantly decreased in failing SR, as assessed by the ratio of the B(max) values for [(3)H]dihydro-FK506 to those for [(3)H]ryanodine binding. In normal SR, the molar ratio was 3.6 ( approximately 1 FKBP12.6 for each RyR monomer), whereas it was 1.6 in failing SR. In normal SR, FK506 caused a dose-dependent Ca(2+) leak that showed a close parallelism with the conformational change in RyR. In failing SR, a prominent Ca(2+) leak was observed even in the absence of FK506, and FK506 produced little or no further increase in Ca(2+) leak and only a slight conformational change in RyR. The level of protein expression of FKBP12.6 was indeed found to be significantly decreased in failing SR.

CONCLUSIONS

An abnormal Ca(2+) leak through the RyR is present in heart failure, and this leak is presumably caused by a partial loss of RyR-bound FKBP12.6 and the resultant conformational change in RyR. This abnormal Ca(2+) leak might possibly cause Ca(2+) overload and consequent diastolic dysfunction, as well as systolic dysfunction.

Roles of the AGE-RAGE system in vascular injury in diabetes

This study concerns whether advanced glycation endproducts (AGE) are related to microvascular derangement in diabetes, exemplified by pericyte loss and angiogenesis in retinopathy and by mesangial expansion in nephropathy. AGE caused a decrease in viable pericytes cultivated from bovine retina. On the other hand, AGE stimulated the growth and tube formation of human microvascular endothelial cells (EC), this being mediated by autocrine vascular endothelial growth factor. In AGE-exposed rat mesangial cells, type IV collagen synthesis was induced. Those AGE actions were dependent on a cell surface receptor for AGE (RAGE), because they were abolished by RAGE antisense or ribozyme. The AGE-RAGE system may thus participate in the development of diabetic microangiopathy. This proposition was supported by experiments with animal models; several indices characteristic of retinopathy were correlated with circulating AGE levels in OLETF rats. The predisposition to nephropathy was augmented in RAGE transgenic mice when they became diabetic.

Identification of a receptor for reg (regenerating gene) protein, a pancreatic beta-cell regeneration factor

Reg (regenerating gene) was isolated as a gene specifically expressed in regenerating islets (Terazono, K., Yamamoto, H., Takasawa, S., Shiga, K., Yonemura, Y., Tochino, Y., and Okamoto, H. (1988) J. Biol. Chem. 263, 2111-2114). Rat and human Reg gene products, Reg/REG proteins, have been demonstrated to stimulate islet beta-cell growth in vitro and in vivo and to ameliorate experimental diabetes. In the present study, we isolated a cDNA for the Reg protein receptor from a rat islet cDNA library. The cDNA encoded a cell surface 919-amino acid protein, and the cells into which the cDNA had been introduced bound Reg protein with high affinity. When the cDNA was introduced into RINm5F cells, a pancreatic beta-cell line that shows Reg-dependent growth, the transformants exhibited significant increases in the incorporation of 5'-bromo-2'-deoxyuridine as well as in the cell numbers in response to Reg protein. A homology search revealed that the cDNA is a homologue to a human multiple exostoses-like gene, the function of which has hitherto been unknown. These results strongly suggest that the receptor is encoded by the exostoses-like gene and mediates a growth signal of Reg protein for beta-cell regeneration.

Identification of a novel Reg family gene, Reg IIIdelta, and mapping of all three types of Reg family gene in a 75 kilobase mouse genomic region

Regenerating gene (Reg), first isolated from a regenerating islet cDNA library, encodes a secretory protein with a growth stimulating effect on pancreatic beta cells that ameliorates the diabetes of 90% depancreatized rats and non-obese diabetic mice. Reg and Reg-related genes have been revealed to constitute a multigene family, the Reg family, which consists of three subtypes (types I, II, III) based on the primary structures of the encoded proteins of the genes. We have isolated three types of mouse Reg family gene (Reg I, Reg II, Reg IIIalpha, Reg IIIbeta and Reg IIIgamma) [Unno et al. (1993) J. Biol. Chem. 268, 15974-15982; Narushima et al. (1997) Gene 185, 159-168]. In the present study, by Southern blot analysis of a mouse bacterial artificial chromosome clone containing the five Reg family genes in combination with PCR cloning of every interspace fragment between adjacent genes, the Reg family genes were mapped to a contiguous 75kb region of the mouse genome according to the following order: 5'-Reg IIIbeta-Reg IIIalpha-Reg II-Reg I-Reg IIIgamma-3'. In the process of ordering the genes, we sequenced the 6.8kb interspace fragment between Reg IIIbeta and Reg IIIalpha and encountered a novel type III Reg gene, Reg IIIdelta. This gene is divided into six exons spanning about 3kb, and encodes a 175 amino acid protein with 40-52% identity with the other five mouse Reg (regenerating gene product) proteins. Reg IIIdelta was expressed predominantly in exocrine pancreas, but not in normal islets, hyperplastic islets, intestine or colon, whereas both Reg I and Reg II were expressed in hyperplastic islets and Reg IIIalpha, Reg IIIbeta and Reg IIIgamma were expressed strongly in the intestinal tract. Possible roles of Reg IIIdelta and the widespread occurrence of the Reg IIIdelta gene in mammalian genomes are discussed.

Autoantibodies to CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) in Caucasian patients with diabetes: effects on insulin release from human islets

The type II transmembrane glycoprotein CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) has been proposed as a mediator of insulin secretion from pancreatic beta-cells and as a candidate for autoimmune reactions in type 2 diabetes. We evaluated the presence of anti-CD38 autoantibodies in Caucasian patients with diabetes and investigated the effect of these antibodies on insulin secretion from isolated human pancreatic islets. The presence of anti-CD38 autoantibodies was evaluated by using Western blot analysis in 236 patients with type 2 diabetes (mean age 63 years), in 160 patients with type 1 diabetes (mean age 38 years), and in 159 nondiabetic subjects. Anti-CD38 autoantibody titers at least 3 SD above the mean value of the control group were found in 9.7% of type 2 diabetic patients and in 13.1% of type 1 diabetic patients (chi2 = 15.9, P = 0.0003 vs. 1.3% of control subjects). No significant differences were observed in sex distribution, current age, age at diabetes onset, BMI, fasting serum glucose, or glycemic control between anti-CD38+ and anti-CD38-diabetic patients in either the type 2 or type 1 diabetic groups. The effect of 23 anti-CD38- and 13 anti-CD38+ sera on insulin secretion at low (3.3 mmol/l) or high (16.7 mmol/l) medium glucose concentrations was evaluated in isolated human pancreatic islets. Data are medians (interquartile range). The anti-CD38+ sera potentiated insulin release both at low [95 (64) vs. 23 (12) microU/ml of control incubations, respectively, P < 0.0001] and high [271 (336) vs. a control of 55 (37) microU/ml, respectively, P = 0.001] medium glucose concentrations, whereas the anti-CD38- sera did not. Furthermore, in the pooled data from all 36 tested sera, insulin levels in the islet incubation medium were directly related to the anti-CD38 antibody titer. We conclude that autoantibodies to CD38 are associated with both type 1 and type 2 diabetes in Caucasian subjects. These autoantibodies exert a stimulatory effect on insulin secretion by cultured human islets. The role of this autoimmune reaction in the pathogenesis of diabetes remains to be elucidated.

Glutathione S-transferase (GST) M1, T1, P1, N-acetyltransferase (NAT) 1 and 2 genetic polymorphisms and susceptibility to colorectal cancer

A case-control study was carried out to examine the relation between genetic polymorphisms of five genes, cigarette smoking and colorectal cancer risk. We collected blood samples from 106 colorectal cancer patients and 100 healthy persons, then analyzed them to identify genotypes for glutathione S-transferase (GST) M1, T1, P1, N-acetyltransferase (NAT) 1 and 2 by the PCR method. We also collected smoking history data from all participants by questionnaire. From statistical evaluation on various combinations of genotypes, we observed that the cancer risk of those who have both GSTM1 present genotype and GSTP1 Adenine/Adenine homozygous genotype was significantly less than those who have other combinations of genotypes for two genes. For other combinations of genes, there was no significant association between genotype and cancer risk. There was also no significant association between amount of cigarette smoking and the cancer risk. These findings suggest that it is valuable to study cancer risk when examining genotypes of more than two genes at the same time. For further study, we need to collect more samples to increase statistical reliability, and besides cigarette smoking, include the nutrition data as an environmental factor.

Human glutathione S-transferase P1 polymorphism and susceptibility to smoking related epithelial cancer; oral, lung, gastric, colorectal and urothelial cancer

The A/G polymorphism at nucleotide 313 in the glutathione S-transferase P1-1 (GSTP1) gene was examined in patients with different types of smoking-related cancers (oral, lung, gastric, colorectal and urothelial cancers) and healthy control individuals. This polymorphism results in an amino acid substitution from isoleucine to valine at residue 105, which reduces catalytic activity of the enzyme. In control individuals, 23.8% of individuals had GSTP1 AG or GG genotype. This rose to 37.3% [n = 83, odds ratio = 1.93 (1.05-3.58), P = 0.035] in oral cancer patients. No increase in the frequency of the GSTP1 AG or GG genotype was obtained in lung, gastric, colorectal or urothelial cancers in this Japanese population. After grouping by smoking status, no consistent difference was observed between smoking patients and corresponding control individuals for the frequency of the GSTP1 A/G polymorphism for any cancer. However, a moderate risk (odds ratio = 2.78; 95% confidence interval 1.06-7.51) was associated with this polymorphism in the non-smoking group of oral cancer patients. The results suggest the GSTP1 polymorphism at nucleotide 313 may be associated with susceptibility to oral squamous cell carcinoma in the Japanese population.

CD38 disruption impairs glucose-induced increases in cyclic ADP-ribose, [Ca2+]i, and insulin secretion

Increases in [Ca2+]i in pancreatic beta cells, resulting from Ca2+ mobilization from intracellular stores as well as Ca2+ influx from extracellular sources, are important in insulin secretion by glucose. Cyclic ADP-ribose (cADPR), accumulated in beta cells by glucose stimulation, has been postulated to serve as a second messenger for intracellular Ca2+ mobilization for insulin secretion, and CD38 is thought to be involved in the cADPR accumulation (Takasawa, S., Tohgo, A., Noguchi, N., Koguma, T., Nata, K., Sugimoto, T., Yonekura, H., and Okamoto, H. (1993) J. Biol. Chem. 268, 26052-26054). Here we created "knockout" (CD38(-/-)) mice by homologous recombination. CD38(-/-) mice developed normally but showed no increase in their glucose-induced production of cADPR in pancreatic islets. The glucose-induced [Ca2+]i rise and insulin secretion were both severely impaired in CD38(-/-) islets, whereas CD38(-/-) islets responded normally to the extracellular Ca2+ influx stimulants tolbutamide and KCl. CD38(-/-) mice showed impaired glucose tolerance, and the serum insulin level was lower than control, and these impaired phenotypes were rescued by beta cell-specific expression of CD38 cDNA. These results indicate that CD38 plays an essential role in intracellular Ca2+ mobilization by cADPR for insulin secretion.

A missense mutation in the CD38 gene, a novel factor for insulin secretion: association with Type II diabetes mellitus in Japanese subjects and evidence of abnormal function when expressed in vitro

Cyclic adenosine 5'diphosphate-ribose (cADPR) is thought to have a second messenger role in insulin secretion through mobilisation of Ca2+. As human lymphocyte antigen CD38 has both ADP-ribosyl cyclase and cADPR hydrolase activity, it may be important in glucose-induced insulin secretion in islets. Thirty one randomly selected Japanese patients with Type II diabetes mellitus who had first-degree and/or second-degree relative(s) with Type II diabetes mellitus were screened for mutations of this gene using single-stranded conformation polymorphism. Two variant patterns in exon 3 and exon 4 of the CD38 gene were identified. The variant in exon 3 resulted in an amino acid substitution from Arg140 (CGG) to Trp (TGG). The Arg140Trp mutation was observed in 4 of 31 patients, and allele frequencies were significantly different in patients and the control subjects (p = 0.004). One patient with this mutation has two missense mutations on beta cell/liver glucose transporter (GLUT2) gene; her mother, who has impaired glucose tolerance, also has this mutation on the CD38 gene and one missense mutation on the GLUT2 gene. Enzyme activity studies using COS-7 cells expressing the Arg140Trp mutation showed a reduction in ADP-ribosyl cyclase and cADPR hydrolase activity of around 50%. The Arg140Trp mutation on CD38 thus appears to contribute to the development of Type II diabetes mellitus via the impairment of glucose-induced insulin secretion in the presence of other genetic defects.

Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients

Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca2+ mobilization for insulin secretion by glucose in pancreatic beta cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD+ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P </= 0.05). Insulin secretion from pancreatic islets by glucose is significantly inhibited by the addition of the NIDDM sera with anti-CD38 antibodies (P </= 0.04-0.0001), and the inhibition of insulin secretion is abolished by the addition of recombinant CD38 (P </= 0.02). The increase of cADPR levels in pancreatic islets by glucose was also inhibited by the addition of the sera (P </= 0.05). These results strongly suggest that the presence of anti-CD38 autoantibodies in NIDDM patients can be one of the major causes of impaired glucose-induced insulin secretion in NIDDM.

Cyclic ADP-ribose and inositol 1,4,5-trisphosphate as alternate second messengers for intracellular Ca2+ mobilization in normal and diabetic beta-cells

Intracellular Ca2+ mobilization occurs in a variety of cellular processes and is mediated by two major systems, the inositol 1,4, 5-trisphosphate (IP3) and cyclic ADP-ribose (cADPR) systems. cADPR has been proposed to be a second messenger for insulin secretion induced by glucose in pancreatic beta-cells (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). Here we show that the cADPR signal system for insulin secretion is replaced by the IP3 system in diabetic beta-cells such as ob/ob mouse islets and RINm5F cells. We measured the cADPR content in these beta-cells by radioimmunoassay and found that the increase of the cADPR content by glucose did not occur in ob/ob mouse islets and RINm5F cells, whereas the increased cADPR level by glucose was observed in normal rat and mouse islets. Microsomes of these diabetic beta-cells released Ca2+ in response to IP3 but not to cADPR. In the diabetic beta-cells, CD38 (ADP-ribosyl cyclase/cADPR hydrolase) and type 2 ryanodine receptor mRNAs were scarcely detected and, in contrast, an increased expression of IP3 receptor mRNAs was observed. The diabetic beta-cells secreted insulin rather by carbamylcholine than by glucose.

Transgenic mice overexpressing type 2 nitric-oxide synthase in pancreatic beta cells develop insulin-dependent diabetes without insulitis

We generated transgenic mice carrying the mouse type 2 nitric-oxide synthase (NOS2) cDNA under the control of the insulin promoter. Western and immunohistochemical analyses revealed that NOS2 was expressed abundantly in transgenic islets but not in control islets. When islets were isolated and cultured, high levels of nitrite were released from the transgenic islets. In transgenic mice, the beta cell mass was markedly reduced without the infiltration of macrophages or lymphocytes, and extensive DNA strand breaks were detected in the islets by in situ nick translation. All the transgenic mice developed hypoinsulinemic diabetes by 4 weeks of age, and treatment with an inhibitor of NOS2, aminoguanidine (200 mg/kg body weight every 12 h), prevented or delayed the development of diabetes. The present study shows that the production of nitric oxide by beta cell NOS2 plays an essential role in the beta cell degeneration.

Muscarinic receptor-mediated dual regulation of ADP-ribosyl cyclase in NG108-15 neuronal cell membranes

Cyclic ADP-ribose (cADP-ribose) is an endogenous modulator of ryanodine-sensitive Ca2+ release channels. An unsolved question is whether or not cADP-ribose mediates intracellular signals from hormone or neurotransmitter receptors. The first step in this study was to develop a TLC method to measure ADP-ribosyl cyclase, by which conversion of [3H]NAD+ to [3H]cADP-ribose was confirmed in COS-7 cells overexpressing human CD38. A membrane fraction of NG108-15 neuroblastoma x glioma hybrid cells possessed ADP-ribosyl cyclase activity measured by TLC. Carbamylcholine increased this activity by 2.6-fold in NG108-15 cells overexpressing m1 or m3 muscarinic acetylcholine receptors (mAChRs), but inhibited it by 30-52% in cells expressing m2 and/or m4 mAChRs. Both of these effects were mimicked by GTP. Pretreatment of cells with cholera toxin blocked the activation, whereas pertussis toxin blocked the inhibition. Application of carbamylcholine caused significant decreases in NAD+ concentrations in untreated m1-transformed NG108-15 cells, but an increase in cholera toxin-treated cells. These results suggest that mAChRs couple to ADP-ribosyl cyclase within cell membranes via trimeric G proteins and can thereby control cellular function by regulating cADP-ribose formation.

A novel action of collapsin: collapsin-1 increases antero- and retrograde axoplasmic transport independently of growth cone collapse

Chick collapsin-1, a member of the semaphorin family, has been implicated in axonal pathfinding as a repulsive guidance cue. Collapsin-1 induces growth cone collapse via a pathway which may include CRMP-62 and heterotrimeric G proteins. CRMP-62 protein is related to UNC-33, a nematode neuronal protein required for appropriately directed axonal extension. Mutations in unc-33 affect neural microtubules, the basic cytoskeletal elements for axoplasmic transport. Using computer-assisted video-enhanced differential interference contrast microscopy, we now demonstrate that collapsin-1 potently promotes axoplasmic transport. Collapsin-1 doubles the number of antero- and retrograde-transported organelles but not their velocity. Collapsin-1 decreases the number of stationary organelles, suggesting that the fraction of time during which a particle is moving is increased. Collapsin-1-stimulated transport occurs by a mechanism distinct from that causing growth cone collapse. Pertussis toxin (PTX) but not its B oligomer blocks collapsin-induced growth cone collapse. The holotoxin does not affect collapsin-stimulated axoplasmic transport. Mastoparan and a myelin protein NI-35 induce PTX-sensitive growth cone collapse but do not stimulate axoplasmic transport. These results provide evidence that collapsin has a unique property to activate axonal vesicular transport systems. There are at least two distinct pathways through which collapsin exerts its actions in developing neurons.

Role of cyclic ADP-ribose in ATP-activated potassium currents in alveolar macrophages

There is growing evidence that extracellular ATP causes a dramatic change in the membrane conductance of a variety of inflammatory cells. In the present study, using the nystatin perforated patch recording configuration, we found that ATP (0.3-30 microM) induced a transient outward current in a concentration-dependent manner and that the reversal potential of the ATP-induced outward current was close to the K+ equilibrium potential, indicating that the membrane behaves like a K+ electrode in the presence of ATP. The first application of ATP to alveolar macrophages perfused with Ca2+-free external solution could induce the outward current, but the response to ATP was diminished with successive applications. Intracellular perfusion with a Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid, also diminished the response. When cyclic ADP-ribose (cADPR) was applied to the macrophage cytoplasm, a transient outward current was elicited. Thereafter, the successive outward current was inhibited, suggesting the involvement of cADPR in the response. Intracellular perfusion with inositol 1,4, 5-trisphosphate also induced a transient outward current, but the successive current was not inhibited. The ATP-induced outward current was abolished when 8-amino-cADPR (as a blocker of cADPR, 10(-6)-10(-5) M) was introduced into the cytoplasm. Homogenates of alveolar macrophages showed both ADP-ribosyl cyclase and cADPR hydrolase activities, and CD38 (ADP-ribosyl cyclase/cADPR hydrolase) expression was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. These results indicate that ATP activates K+ currents by releasing Ca2+ from cADPR-sensitive internal Ca2+ stores.

Attenuation of nitric oxide synthase induction in IRF-1-deficient glial cells

Nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) exerts inhibitory and cytotoxic effects on various cells including neuronal cells. Glial NO production, mediated via induction of iNOS, is thought to facilitate neuronal damage during cerebral ischemia. Recently, interferon regulatory factor-1 (IRF-1) has been reported to be an essential transcription factor for iNOS mRNA induction in murine macrophages. However, expression of IRF-1 and its role in the central nervous system have not been examined. In the present study, by using primary glial cell cultures from mice with targeted disruption of the IRF-1 gene, we investigated whether IRF-1 is involved in iNOS mRNA induction in glial cells. After stimulation with lipopolysaccharide and interferon-gamma, IRF-1 mRNA was strongly induced in wild-type (IRF-1 +/+) glial cells. iNOS mRNA induction and nitrite production in IRF-1 -/- glial cells were reduced as compared with those observed in IRF-1 +/+ glial cells. Diethyldithiocarbamate, a selective inhibitor of nuclear transcription factor kappa B (NF-kappa B), completely inhibited iNOS mRNA induction. These results suggest that not only NF-kappa B but also IRF-1 play important roles in iNOS mRNA induction in the central nervous system.

Human gene encoding CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase): organization, nucleotide sequence and alternative splicing

We have recently demonstrated that cyclic ADP-ribose (cADPR) serves as a second messenger for glucose-induced insulin secretion [Takasawa et al. (1993a) Science 259, 370-373] and that CD38 has both ADP-ribosyl cyclase (ADRC) and cADPR hydrolase activities [Takasawa et al. (1993b) J. Biol. Chem. 268, 26052-26054]. In this study, we determined the structure of the human CD38 gene, and showed that two mRNA forms originated by alternative splicing from the CD38 gene. The human CD38 gene consists of 8 exons that extend more than 77 kb on the human genome. Exon 1 encoded the 5'-untranslated region of the mRNA, the N-terminal end of CD38 and the putative transmembrane domain, and exon 2-8 encoded the remainder of CD38: the exon-intron organization of the human CD38 gene is similar to that of the Aplysia ADRC gene [Nata et al. (1995) Gene 158, 213-218]. This structural conservation between human and Aplysia genes suggests that both genes may have evolved from a common ancestral gene.

Lysine 129 of CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) participates in the binding of ATP to inhibit the cyclic ADP-ribose hydrolase

CD38 catalyzes not only the formation of cyclic ADP-ribose (cADPR) from NAD+ but also the hydrolysis of cADPR to ADP-ribose (ADPR), and ATP inhibits the hydrolysis (Takasawa, S., Tohgo, A., Noguchi, N., Koguma, T., Nata, K., Sugimoto, T., Yonekura, H., and Okamoto, H. (1993) J. Biol. Chem. 268, 26052-26054). In the present study, using purified recombinant CD38, we showed that the cADPR hydrolase activity of CD38 was inhibited by ATP in a competitive manner with cADPR. To identify the binding site for ATP and/or cADPR, we labeled the purified CD38 with FSBA. Sequence analysis of the lysylendopeptidase-digested fragment of the labeled CD38 indicated that the FSBA-labeled residue was Lys-129. We introduced site-directed mutations to change the Lys-129 of CD38 to Ala and to Arg. Neither mutant was labeled with FSBA nor catalyzed the hydrolysis of cADPR to ADPR. Furthermore, the mutants did not bind cADPR, whereas they still used NAD+ as a substrate to form cADPR and ADPR. These results indicate that Lys-129 of CD38 participates in cADPR binding and that ATP competes with cADPR for the binding site, resulting in the inhibition of the cADPR hydrolase activity of CD38.

Cyclic ADP-ribose binds to FK506-binding protein 12.6 to release Ca2+ from islet microsomes

Cyclic ADP-ribose (cADPR) is a second messenger for Ca2+ mobilization via the ryanodine receptor (RyR) from islet microsomes for insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). In the present study, FK506, an immunosuppressant that prolongs allograft survival, as well as cADPR were found to induce the release of Ca2+ from islet microsomes. After islet microsomes were treated with FK506, the Ca2+ release by cADPR from microsomes was reduced. cADPR as well as FK506 bound to FK506-binding protein 12.6 (FKBP12.6), which we also found occurs naturally in islet microsomes. When islet microsomes were treated with cADPR, FKBP12.6 dissociated from the microsomes and moved to the supernatant, releasing Ca2+ from the intracellular stores. The microsomes that were then devoid of FKBP12.6 did not show Ca2+ release by cADPR. These results strongly suggest that cADPR may be the ligand for FKBP12.6 in islet RyR and that the binding of cADPR to FKBP12.6 frees the RyR from FKBP12.6, causing it to release Ca2+.

Structure, chromosomal localization and expression of mouse genes encoding type III Reg, RegIII alpha, RegIII beta, RegIII gamma

Reg (regenerating gene), first isolated from a rat regenerating islet cDNA library, is expressed in regenerating islet beta-cells. Recently, it has been revealed that Reg and Reg-related genes constitute a multigene family, Reg family, which consists of three subtypes (type I, II, III) based on the primary structures of the encoded proteins of the genes. In mouse, type I and type II Reg genes (i.e. RegI and RegII gene) have so far been isolated. In the present study, the complete nucleotide (nt) sequences of the cDNAs and genes encoding murine type III Reg (regenerating gene product), RegIII alpha, RegIII beta and RegIII gamma were determined. RegIII alpha, RegIII beta and RegIII gamma encode 175-, 175- and 174-amino acid (aa) proteins, respectively, with 60-70% homology. All three genes are composed of six exons and five introns spanning approx. 3 kb, and exhibit distinctive structural features unique for members of the Reg gene family. All the mouse Reg genes, RegIII alpha, RegIII beta, RegIII gamma, RegI and RegII, are assigned to the adjacent site of chromosome 6C by fluorescence in situ hybridization (FISH). RegIII alpha, RegIII beta and RegIII gamma were expressed weakly in pancreas, strongly in intestinal tract, but not in hyperplastic islets, whereas both RegI and RegII were expressed in hyperplastic islets. These results suggest that genes of the mouse Reg family are derived from a common ancestor gene by several gene duplications, and have obtained divergency in expression and function in the process of genetic evolution.

Enhancement of glucose-induced insulin secretion in transgenic mice overexpressing human VIP gene in pancreatic beta cells

Using transgenic mice technology, it has now become possible to test directly whether VIP and PHM-27 can enhance glucose-induced insulin secretion and reduce blood glucose in vivo. By microinjecting the entire human VIP gene ligated to the rat insulin II promoter, we have established a mouse model that overproduces VIP and PHM-27 in pancreatic beta cells. VIP was secreted from transgenic islets in a glucose-dependent manner. Analyses of these VIP-transgenic mice indicated that the transgene efficiently enhances glucose-induced insulin secretion and significantly reduces blood glucose as compared with control mice. The transgene also ameliorated glucose intolerance of 70% depancreatized mice. The present results suggest that somatic cell gene therapy directed to diabetic islets by human VIP/PHM-27 gene introduction may provide a means to improve the secretory function of the diabetic islets.

Reg gene expression is increased in rat gastric enterochromaffin-like cells following water immersion stress

BACKGROUND & AIMS

Reg gene has been isolated from regenerating rat pancreatic islets, and subsequent studies have shown a trophic effect of Reg protein on islet cells. However, little is known about the role of Reg protein in the stomach. The aim of this study was to clarify the localization of Reg messenger RNA (mRNA) and its product in the stomach and to examine changes in the level of their expression during regeneration of gastric mucosal cells.

METHODS

Gastric lesions were experimentally induced in Sprague-Dawley rats by water immersion stress. Northern blot analysis and in situ hybridization studies were performed to examine changes in mRNA levels. Immunohistochemical studies were performed to identify the cellular localization and to investigate the change in Reg protein level.

RESULTS

Reg mRNA and its product were distributed in the basal part of the oxyntic mucosa and were expressed mainly in enterochromaffin-like cells. Levels of both Reg mRNA and its product were markedly increased in the water immersion-induced gastric lesions.

CONCLUSIONS

Reg mRNA and its product are expressed in gastric enterochromaffin-like cells, and their levels are increased during the healing process of water immersion-induced gastric lesions.

Identification of the five essential histidine residues for peptidylglycine monooxygenase

Peptidylglycine monooxygenase (PGM) is a copper-containing monooxygenase that plays a key role in the peptide C-terminal alpha-amidation. Comparative analysis of the amino acid sequences of rat, human, bovine and frog PGMs revealed that ten histidines (residues 107, 108, 172, 235, 242, 244, 279, 364, 366 and 367 in rat PGM) are conserved among the four species. We introduced site-directed mutations to the ten histidines of rat PGM and found that the mutation of His- 107-->Ala, His-108-->Ala, His-172-->Ala, His-242-->Arg or His-244-->Ala abolished the enzyme activity. The five mutant proteins lacking the enzyme activity bound to a substrate, Phe-Gly-Phe-Gly, as did the wild type PGM. These results along with available evidence indicate that the five histidine residues (His-107, 108, 172, 242 and 244) are essential for PGM activity, acting as copper ligands.

Human REG family genes are tandemly ordered in a 95-kilobase region of chromosome 2p12

Reg, first isolated from a rat regenerating islet cDNA library, is expressed in regenerating islet beta-cells. Recently, it has been revealed that Reg and Reg-related genes constitute a multigene family, the Reg family. In human, the four REG family genes, i.e., REG 1 alpha, REG 1 beta, REG-related sequence (RS) and HIP/PAP, have so far been isolated. In this study, we analyzed YAC clones containing the four genes and performed two-color FISH to determine the map order of the genes. The human REG family genes are tandemly ordered in the 95-kbp DNA region of chromosome 2p12 as follows: 2cen-HIP/PAP-RS-REG I alpha-REG I beta-ptel.

Requirement of calmodulin-dependent protein kinase II in cyclic ADP-ribose-mediated intracellular Ca2+ mobilization

Cyclic ADP-ribose (cADPR) is generated in pancreatic islets by glucose stimulation, serving as a second messenger for Ca2+ mobilization from the endoplasmic reticulum for insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). In the present study, we observed that the addition of calmodulin (CaM) to rat islet microsomes sensitized and activated the cADPR-mediated Ca2+ release. Inhibitors for CaM-dependent protein kinase II (CaM kinase II) completely abolished the glucose-induced insulin secretion as well as the cADPR-mediated and CaM-activated Ca2+ mobilization. Western blot analysis revealed that the microsomes contain the alpha isoform of CaM kinase II but do not contain CaM. When the active 30-kDa chymotryptic fragment of CaM kinase II was added to the microsomes, fully activated cADPR-mediated Ca2+ release was observed in the absence of CaM. These results along with available evidence strongly suggest that CaM kinase II is required to phosphorylate and activate the ryanodine-like receptor, a Ca2+ channel for cADPR as an endogenous activator, for the cADPR-mediated Ca2+ release.