Parathyroid tumor suppressor on 1p: analysis of the p18 cyclin-dependent kinase inhibitor gene as a candidate

Loss of chromosome arm 1p DNA is the most common molecular defect thus far observed in human parathyroid adenomas, suggesting that 1p is the location of a putative tumor suppressor gene (or genes) whose inactivation contributes frequently to parathyroid tumorigenesis. To narrow the genomic location of this tumor suppressor gene, we analyzed 25 sporadic parathyroid adenomas for allelic loss of polymorphic DNA loci on chromosome 1 using 11 microsatellite markers not previously scored for this set of tumors. Allelic loss on chromosome arm 1p DNA was observed in 8 of 25 adenomas. Marker deletion patterns showed some complexity, with the regions most commonly deleted in these tumors being 1p36 and 1p35-p31. The 1p35-p31 region contains an excellent candidate tumor suppressor gene, p18, whose product is a cell cycle regulator that inhibits the cyclin D1-associated kinase CDK6. Given that cyclin D1 is a parathyroid oncogene, inactivation of an inhibitor of cyclin D1 function, like p18, might also cause excessive parathyroid growth. To examine the involvement of p18 in parathyroid tumorigenesis, we analyzed 25 parathyroid adenomas for mutations of the p18 coding exons by single strand conformational polymorphism analysis and sequencing. No point mutations were found in any of the 25 adenomas. These observations indicate that inactivating mutation of the p18 gene occurs uncommonly, if at all, in parathyroid adenomas. In addition, the data raise the important possibility that more than a single tumor suppressor gene on 1p could contribute to parathyroid neoplasia.

Trimeresurus stejnegeri snake venom plasminogen activator. Site-directed mutagenesis and molecular modeling

The specific plasminogen activator from Trimeresurus stejnegeri venom (TSV-PA) is a serine proteinase presenting 23% sequence identity with the proteinase domain of tissue type plasminogen activator, and 63% with batroxobin, a fibrinogen clotting enzyme from Bothrops atrox venom that does not activate plasminogen. TSV-PA contains six disulfide bonds and has been successfully overexpressed in Escherichia coli (Zhang, Y., Wisner, A., Xiong, Y. L., and Bon, C. (1995) J. Biol. Chem. 270, 10246-10255). To identify the functional domains of TSV-PA, we focused on three short peptide fragments of TSV-PA showing important sequence differences with batroxobin and other venom serine proteinases. Molecular modeling shows that these sequences are located in surface loop regions, one of which is next to the catalytic site. When these sequences were replaced in TSV-PA by the equivalent batroxobin residues none generated either fibrinogen-clotting or direct fibrinogenolytic activity. Two of the replacements had little effect in general and are not critical to the specificity of TSV-PA for plasminogen. Nevertheless, the third replacement, produced by the conversion of the sequence DDE 96a-98 to NVI, significantly increased the Km for some tripeptide chromogenic substrates and resulted in undetectable plasminogen activation, indicating the key role that the sequence plays in substrate recognition by the enzyme.

[Immuno-enhancing effect of gebie oral liquid on mice]

Gebie Oral Liquid can increase the weight of thymus and spleen of the mouse, damaged by prednisone and cytoxan, enhance the phagocytosis of monocytes and DHT, and promote the blastogenesis of splenic lymphocytes as well as the activity of NK cells.

Mitochondrial dysfunction after experimental and human brain injury and its possible reversal with a selective N-type calcium channel antagonist (SNX-111)

We have recently demonstrated in a rat model that traumatic brain injury induces perturbation of cellular calcium homeostasis with an overload of cytosolic calcium and excessive calcium adsorbed on the mitochondrial membrane, consequently the mitochondrial respiratory chain-linked oxidative phosphorylation was impaired. We report the effect of a selective N-type calcium channel blocker, SNX-111 on mitochondrial dysfunction induced by a controlled cortical impact. Intravenous administration of SNX-111 at varying times post injury was made. The concentration titration profile revealed SNX-111 at 4 mg kg-1 to be optimal, and the time window to be administration at 4 h post-injury, in line with that reported on the effect of SNX-111 in experimental stroke. Under optimal conditions, SNX-111 significantly improved the mitochondrial respiratory chain-linked functions, such as the electron transfer activities with both succinate and NAD-linked substrates, and the accompanied energy coupling capacities measured as respiratory control indices (RCI) and ATP synthesis (P/O ratio), and the energy linked Ca2+ transport. In order to assess the applicability of these data to the clinical setting, we have initiated studies with brain tissue which has to be resected during surgical treatment. Five patients suffered from brain trauma, one from intracranial hypertension due to stroke (noninfarcted tissue was taken), and one from epilepsy. Our data revealed that brain mitochondria derived from the patient with intracranial hypertension and the patient with epilepsy were tightly coupled with good respiratory rates with glutamate and malate as substrates, and high P/O ratios. The rates of respiration and ATP synthesis were severely impaired in the brain mitochondria isolated from traumatized patients. These results indicate that investigation of brain mitochondrial functions can be used as a measure for trauma-induced impairment of brain energy metabolism. The time window for the effect of SNX-111 in mitochondrial function and the (preliminary) similarity between mitochondrial dysfunction in experimental animals and humans make the drug appear to be well suited for clinical trials in severe head injury.

Acetaminophen cytotoxicity in mouse eye: mitochondria in anterior tissues are the primary target

Acetaminophen (APAP) injected into C57BL/6 mice (cytochrome P450 inducer-responsive strain) that had been pretreated with b-naphthoflavone (BNF) produced ocular tissue damage, including cataract. Our previous histocytochemical studies showed that tissue damage spread in association with the flow of the aqueous humor and appeared first in the ciliary epithelium, followed by the iris and corneal endothelium and, finally, the lens. The neural retina, retinal pigmented epithelium and choroid remained unaffected. A close examination of the affected tissues indicated that mitochondria are the primary target of APAP cytotoxicity. In order to investigate whether the respiratory capacity of mitochondria is more sensitive to APAP cytotoxicity than mitochondrial morphology, we determined in this work the oxygen uptake by eye tissues dissected from BNF-pretreated and APAP-injected C57BL/6 mice. Oxygen uptake by the ciliary body/iris decreased about 60% at 90 min and 85% at 120 min after APAP administration. The oxygen uptake was inhibited about 50% by 10 microM rotenone. Since the earliest sign of mitochondrial damage was noted at 120 min, the result indicates that mitochondrial energy dysfunction precedes morphological alterations. It was also observed that oxygen uptake by the retina remained unaffected at least for 120 min after APAP administration; therefore, it is evident that the retina and, possibly, other posterior tissues as well are resistant to APAP cytotoxicity, not only in their morphology but, also, in their capacity of mitochondrial energy metabolism.

Purification and characteristics of recombinant mouse metallothionein-I from Escherichia coli

The mouse metallothionein-I (mMT-I) cDNA was amplified by polymerase chain reaction (PCR), inserted into vector pGEX-4T-1, and expressed in Escherichia coli as a carboxyl terminal extension of the 26-kDa glutathione-S-transferase (GST). Analyzed by SDS-PAGE, the amount of the expressed fusion protein GST-MT was over 50% of total cellular proteins. After the fusion protein had been digested with thrombin on a Glutathione-Sepharose 4B affinity chromatography column, recombinant mMT-I was purified by gel filtration on Sephadex G50. The results of molecular mass, amino acid composition and sequence of 10 amino acids at the N-terminus of the recombinant mMT-I demonstrate that the purified protein is the one we desired. The ratios of metal:protein and thiol:protein are the same as those of wild-type MT. The half-dissociation pHs of Cd, Cu, and Zn from recombinant mMT-I were 3.57, 1.40, and 5.20, respectively, which are in agreement with those from native rabbit MT-I. The ultraviolet absorbance and circular dichroism (CD) spectra at pH 8.0 and pH 2.0 were all similar to those of native MT, indicating that they have the same metal-thiolate structure even though six amino acid residues have been added at the N-terminus of the recombinant protein.

Differences in the density of barosensitive neurons in the medulla of spontaneously hypertensive and Wistar-Kyoto rats

1. The density of barosensitive neurons in the medulla was examined in spontaneously hypertensive rats (SHR) and in normotensive Wistar-Kyoto (WKY) rats. In control experiments, rats were sham-operated, while in test experiments arterial baroreceptors were stimulated by pressor responses to i.v. administration of phenylephrine and the density of c-Fos-labelled neurons was immunocytologically examined. 2. In both control and test experiments, c-Fos-labelled neurons were distributed in cardiovascular control sites: the nucleus tractus solitarii (NTS) and the caudal and rostral ventrolateral medullas (CVLM/RVLM). 3. In both WKY rats and in SHR, the total density of labelled neurons in test experiments was significantly higher than in control experiments. 4. In control experiments, no significant difference was found in the distribution and density of labelled neurons in the NTS and in the CVLM/RVLM between rats and SHR. 5. In test experiments, no significant difference was found in the distribution and density of labelled neurons in the NTS between WKY rats and SHR. 6. In test experiments in SHR, the density of labelled neurons in the CVLM just caudal to the obex level was significantly higher than that in WKY rats, whereas the density of labelled neurons in WKY rats in the RVLM just rostral to the obex level was significantly higher than that in SHR. 7. These results indicate that stimulation of the arterial baroreceptor induces strain-specific differences in the density of barosensitive neurons in the CVLM/RVLM near the obex level.

Interleukin-1beta is differentially expressed by human dermal papilla cells in response to PKC activation and is a potent inhibitor of human hair follicle growth in organ culture

The dermal papilla plays an important role in the regulation of hair follicle matrix cell proliferation and hair fiber production, at least in part through mesenchymal-epithelial interactions. In the present study, we have investigated the regulation of interleukin-1 (IL-1) production by protein kinase C in cultured human dermal papilla cells. Treatment of dermal papilla cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) elicited the rapid and transient production of mature (17 kDa) cytosolic IL-1beta protein, but not IL-1alpha, with maximal levels achieved after 12 h. Rapid secretion of IL-1beta into the medium occurred subsequent to increased intracellular cytokine levels, after which medium IL-1beta protein levels were stable for 4 days. Northern blot analysis showed that TPA treatment elicited a transient induction of IL-1beta mRNA expression, maximal after 12 h, indicating that TPA regulates dermal papilla cell IL-1beta production at the transcriptional level. Pretreatment of dermal papilla cells with Ro 31-7549, a selective protein kinase C inhibitor, dose dependently and completely reversed phorbol-induced IL-1beta protein production. In addition, we demonstrated that IL-1beta is a highly potent inhibitor of the growth of human hair follicles in whole-organ culture, with an IC50 value of approximately 5 pg/ml. These findings, taken together with a previous report that follicular matrix cells express type I IL-1 receptors but dermal papilla cells do not, raise the possibility that dermal papilla cell-derived IL-1beta may act as a negative paracrine factor in the regulation of matrix cell proliferation.

[The anti-inflammatory effects of superoxide dismutase]

This paper reports the anti-inflammatory effects of superoxide dismutase (SOD) from pig blood on inflammatory animal models. The experimental results have shown that SOD has significant anti-inflammatory effects. It inhibited carrageenin-induced foot-edema and croton oil induced granulation tissue edema of rats. It also inhibited arthritis induced by egg serum and Freund's adjuvant in rats. The effects were significantly dose-dependent.

Induction of cell cycle arrest and B cell terminal differentiation by CDK inhibitor p18(INK4c) and IL-6

Cell cycle arrest and cell death are tightly coupled to terminal differentiation of B cells to plasma cells in vivo. This process was recapitulated in vitro by stimulation of IgG-bearing human B lymphoblastoid cells with interleukin-6 (IL-6), which led to orderly cell cycle arrest, differentiation, and apoptosis. In terminally differentiated plasmacytoid cells, phosphorylation of pRb was suppressed, correlating with the activation of the D-type cyclin-dependent kinase (CDK) inhibitors p18(INK4c) and p21(WAF1/CIP1). The expression of CDK6, however, remained unchanged. Activation of p18 by IL-6 was rapid, concomitant with marked enhancement of its association with CDK6 and cell cycle arrest. Overexpression of p18 in IgM-bearing lymphoblastoid cells, which differentiated in response to IL-6 but did not exit the cell cycle, reconstituted coupled differentiation and cell cycle arrest. Thus, CDK inhibitors, in particular p18, are likely to play a pivotal role in controlling cell cycle arrest and cell death in terminal differentiation of late-stage B cells to plasma cells via inhibition of pRb phosphorylation by CDK6.

Preliminary studies on the relationship between autoantibodies to heat stress proteins and heat injury of pilots during acute heat stress

Comparison in the heart rate, oral temperature and lymphocyte DNA damage during heat stress was made in pilots with negative antibodies to heat stress proteins (HSPs) and those with positive antibodies in the man-made climate room with Western blot and comet assay. Our results showed that the increase in oral temperature, heart rate and lymphocyte DNA damage in pilots with the positive antibodies to HSPs were higher than those in pilots with the negative antibodies during heat stress. These results indicated that the presence of autoantibodies in plasma of pilots might reflect heat damage and high sensitivity to heat.

Mitochondrial dysfunction and calcium perturbation induced by traumatic brain injury

Traumatic brain injury (TBI) is associated with primary and secondary injury. A thorough understanding of secondary injury will help to develop effective treatments and improve patient outcome. In this study, the GM model of controlled cortical impact injury (CCII) of Lighthall (1988) was used with modification to induce lateral TBI in rats. Forebrain mitochondria isolated from ipsilateral (IH) and contralateral (CH) hemispheres to impact showed a distinct difference. With glutamate + malate as substrates, mitochondria from the IH showed a significant decrease in State 3 respiratory rates, respiratory control indices (RCI), and P/O ratios. This decrease occurred as early as 1 h and persisted for at least 14 days following TBI. The State 3 respiratory rates, RCI, and P/O ratios could be restored to sham values by the addition of EGTA to the assay mixture. A significant amount of Ca2+ was found to be adsorbed to the mitochondria of both the IH and the CH with higher values seen in the IH. The rate of energy-linked Ca2+ transport in the IH was significantly decreased at 6 and 12 h. These data indicate that CCII-induced TBI perturbs cellular Ca2+ homeostasis and results in excessive Ca2+ adsorption to the mitochondrial membrane, which subsequently inhibits the respiratory chain-linked electron transfer and energy transduction.

Molecular analysis of the cyclin-dependent kinase inhibitor genes p15INK4b/MTS2, p16INK4/MTS1, p18 and p19 in human cancer cell lines

Cyclin-dependent kinase-4 inhibitor genes (INK4) regulate the cell cycle and are candidate tumor-suppressor genes. To determine if alterations in the coding regions of the p18 and p19 genes, which are novel members of the INK4 family and if they correlate with the development of human cancer, 100 human cancer cell lines were analyzed. Two other INK4 gene family members, p15INK4b/MTS2 and p16INK4/MTS1 genes were also analyzed. Homozygous deletions of the p15INK4b/MTS2 gene were detected in 29 cancer cell lines. Thirty-five homozygous deletions and 7 intragenic mutations of the pl6INK4/MTS1 gene were also detected in these cell lines. Neither homozygous deletions nor intragenic mutations of the p18 and p19 genes were found except in an ovarian cancer cell line, SKOV3, harboring a single base pair deletion in exon 1 of p19. In p16INK4/MTS1 expression analysis, 5 cell lines with both authentic and alternative spliced p16INK4/MTS1 mRNA had no detectable p16INK4/MTS1 protein. These results suggest the hypotheses that either post-translational modification or enhanced degradation may be responsible for the lack of detection of the p16INK4/MTS1 protein. Using Western blot analysis, subsets of 26 human cancer cell lines were examined for p18 expression and 39 cell lines for p19 expression. All of these cell lines expressed the p18 or p19 protein, with the exception of SKOV3, which did not express p19. Therefore, the INK4 gene family may be divided into 2 groups. One group includes p15INK4b/MTS2 and p16INK4/MTS1, in which genetic and epigenetic alterations might contribute to the development of human cancers. The other group includes p18 and p19, in which somatic mutations are uncommon in many types of human cancer, and their role in human carcinogenesis and cancer progression is uncertain.

Involvement of the cyclin-dependent kinase inhibitor p16 (INK4a) in replicative senescence of normal human fibroblasts

Human diploid fibroblasts (HDFs) can be grown in culture for a finite number of population doublings before they cease proliferation and enter a growth-arrest state termed replicative senescence. The retinoblastoma gene product, Rb, expressed in these cells is hypophosphorylated. To determine a possible mechanism by which senescent human fibroblasts maintain a hypophosphorylated Rb, we examined the expression levels and interaction of the Rb kinases, CDK4 and CDK6, and the cyclin-dependent kinase inhibitors p21 and p16 in senescent HDFs. Cellular p21 protein expression increased dramatically during the final two to three passages when the majority of cells lost their growth potential and neared senescence but p21 levels declined in senescent HDFs. During this period, p16 mRNA and cellular protein levels gradually rose with the protein levels in senescent HDFs reaching nearly 40-fold higher than early passage cells. In senescent HDFs, p16 was shown to be complexed to both CDK4 and CDK6. Immunodepletion analysis of p21 and p16 from the senescent cell extracts revealed that p16 is the major CDK inhibitor for both CDK4 and CDK6 kinases. Immunoprecipitation of CDK4 and CDK6 and their associated proteins from radiolabeled extracts from senescent HDFs showed no other CDK inhibitors. Based upon these results, we propose that senescence is a multistep process requiring the expression of both p21 and p16. p16 up-regulation is a key event in the terminal stages of growth arrest in senescence, which may explain why p16 but not p21 is commonly mutated in immortal cells and human tumors.

Lack of mutation in the cyclin-dependent kinase inhibitor, p19INK4d, in tumor-derived cell lines and primary tumors

Inhibitors of cyclin-dependent kinases provide a major mechanism of negative regulation on cell cycle progression. Defects in the function of the CDK inhibitors may lead to uncontrolled cell proliferation and potentially facilitate tumorigenesis. The p16INK4 family of CDK inhibitors specifically prevent the phosphorylation of the retinoblastoma susceptibility gene product, pRb, by inhibiting the kinase activity of CDK4 and CDK6, thereby keeping pRb in its active form as a growth suppressor. The loss of p16INK4 inhibitory activity would, therefore, have the same consequence as the loss of pRb growth suppressing activity. The p16INK4 family currently includes four members, p15INK4b, pl6INK4a, pl8INK4c and p19INK4d. Two members, p15INK4b and pl6INK4a have been found to be deleted and mutated in a variety of human tumor-derived cell lines and primary tumors. In the present study we have examined the genomic status of the newly isolated p19INK4d gene in 75 tumor-derived cell lines; 13 immortalized, transformed or normal cell lines; 19 ovarian tumors and 18 acute myelogenous leukemias. No deletions or point mutations were observed in the pl9INK4d gene. A genetic polymorphism at codon 30 (CGC-->CGG) in exon 1 of the pl9INK4d gene was observed in 10% of the samples under investigation. In the same set of samples, p16INK4a was found to be homozygously deleted in 32% of the tumor derived cell lines. These results together with our previous data that showed a 22% deletion frequency in p15INK4b and rare alterations in the pl8INK4c gene, indicating that the p16INK4a and pl5INK4b, but not the p18INK4c and pl9INK4d genes, are frequently mutated in human tumors. Hence, members of the p16INK4 CDK inhibitor family, while evolutionary related and biochemically indistinguishable, carry out distinct biological functions.

[Influence of temperature on the chemical constituents and pharmacological effects of semen Cassiae]

The influence of temperature on the chemical constituents and pharmacological effects of seeds of Cassia tora was examined. As the baking temperature was raised, the contents of free chrysophanol increased. The contents of antihepatotoxic constituents in the samples baked at different temperatures were compared. They decreased as the temperature rose. The pharmacological results basically accorded with the contents of the constituents.

Induction of p18INK4c and its predominant association with CDK4 and CDK6 during myogenic differentiation

Terminal cell differentiation involves permanent withdrawal from the cell division cycle. The inhibitors of cyclin-dependent kinases (CDKs) are potential molecules functioning to couple cell cycle arrest and cell differentiation. In murine C2C12 myoblast cells, G1 CDK enzymes (CDK2, CDK4, and CDK6) associate with four CDK inhibitors: p18INK4c, p19INK4d, p21, and p27Kip1. During induced myogenesis, p21 and its associated CDK proteins underwent an initial increase followed by a decrease as cells became terminally differentiated. The level of p27 protein gradually increased, but the amount of total associated CDK proteins remained unchanged. p19 protein decreased gradually during differentiation, as did its associated CDK4 protein. In contrast, p18 protein increased 50-fold, from negligible levels in proliferating myoblasts to clearly detectable levels within 8-12 h of myogenic induction. This initial rise was followed by a precipitous increase between 12 and 24 h postinduction, with p18 protein finally accumulating to its highest level in terminally differentiated cells. Induction of p18 correlated with increased and sequential complex formation--first increasing association with CDK6 and then with CDK4 over the course of myogenic differentiation. All of the CDK6 and half of the CDK4 were complexed with p18 in terminally differentiated C2C12 cells as well as in adult mouse muscle tissue. Finally, kinase activity of CDK2 and CDK4 decreases as C2C12 cells differentiate, whereas the CDK6 kinase activity is low in both proliferating myoblasts and differentiated myotubes. Our results indicate that p18 may play a critical role in causing and/or maintaining permanent cell cycle arrest associated with mature muscle formation.

The protective effects of ischemic and calcitonin gene-related peptide-induced preconditioning on myocardial injury by endothelin-1 in the isolated perfused rat heart

This study was to investigate the effects of ischemic preconditioning on endothelin-1-induced myocardial injury and the role of calcitonin gene-related peptide (CGRP) played in such effects. The rat hearts were perfused in a Langendorff mode. Heart rates (HR), coronary flow (CF), left ventricular pressure (LVP) and its first derivative (LV dp/dtmax) were recorded and creatinine phosphate kinase (CPK) from coronary effluent was measured. There were no changes in HR, CF, LVP, or LV dp/dtmax throughout the experiment in the control hearts. Endothelin-1 (100 pmol) significantly decreased HR and CF, impaired the cardiac function, and increased the CPK release. However, the HR, CF, LVP and LV dp/dtmax were significantly improved, while the CPK release was decreased in the preconditioned hearts. CGRP8-37, a selective CGRP receptor antagonist, abolished the cardioprotection of ischemic preconditioning, such as the cardiac function and the CPK release. A similar cardioprotection was observed in the hearts pretreated with CGRP. However, the CGRP-induced preconditioning-like protection was abolished in the presence of CGRP8-17 or 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, an inhibitor of protein kinase C. The present study suggests that the cardioprotective effect of ischemic preconditioning on endothelin-1-induced myocardial injury is mediated by CGRP, and that the cardioprotection of CGRP-induced preconditioning is related to the activation of protein kinase C.