Seladelicatulasine A-G, C27 steroidal glycosides with cholinesterase inhibitory activities from Selaginella delicatula

Seven undescribed C₂₇ steroidal glycosides, Seladelicatulasine A-G, including six cholestanol glycosides and one spirostanol glycoside, were isolated from Selaginella delicatula. Their structures were elucidated by 1D/2D NMR spectra and HRESIMS analyses. The absolute configurations of the sugars were determined by enzymatic hydrolysis and GC/MS analyses. These cholestanol glycosides were isolated from the family Selaginellaceae for the first time. Seladelicatulasine F is characterized as a rare B-5,6-secosteroid. In addition, all the compounds were evaluated for their inhibitory activities against cholinesterase (AChE/BChE) and monoamine oxidase (MAO-A/MAO-B). These steroidal glycosides displayed selective inhibition activities on cholinesterase. Seladelicatulasine A, B and E inhibited the AChE activity with IC₅₀ values of 0.31, 0.09, and 0.04 μM, respectively. Seladelicatulasine A and F showed the strongest inhibition activity on BChE with IC₅₀ values of 0.37 and 0.65 μM, respectively.

Pictalignans D-F, three new neolignan derivatives from Selaginella picta

Three new neolignan derivatives (1-3), together with three known isolariciresinol derivatives (4-6) were isolated from Selaginella picta. Their structures were elucidated by spectroscopic methods (1D/2D NMR, HRESIMS and CD). All isolated compounds were assayed on the neuroprotective activity against the injury of HT-22 cells induced by L-Glutamate in vitro. All compounds displayed potent protective effect on HT-22 cells.

New adenine analogues and a pyrrole alkaloid from Selaginella delicatula

Phytochemical study on the n-BuOH extract of Selaginella delicatula lead to the isolation, characterization and structure elucidation of two new adenine analogues, delicatulines A (1) and B (2), one new pyrrole alkaloid (4), and five known compounds (3, 5-8). These new substances all contain an aliphatic chain in their parent nucleus, which were unusual to find in plants. In the present study, they were identified from Selaginellaceae for the first time. The structures and absolute configurations of these new compounds were determined by a combination of NMR and CD spectroscopic analyses. Compounds 1, 3 and 4 were evaluated for their inhibitory activities on HBV surface antigen and HBV DNA in HepAD38 cells. The results showed that these compounds had only weak or no inhibitive effects on HBV.

Study on the adsorption of cadmium(II) from aqueous solution by D152 resin

The feasibility of using D152 resin as an adsorbent for cadmium(II) was examined. The adsorption capacity of D152 resin for cadmium(II) ions was studied as a function of solution pH, temperature and contact time. The optimal pH for the adsorption of cadmium(II) ions was found to be 5.95 in the HAc-NaAc system. The maximum uptake capacity of cadmium(II) was estimated to 378 mg/g D152 resin at 298 K, at an initial pH value of 5.95. The results obtained from equilibrium adsorption studies were conformed to the Langmuir and Freundlich and the correlation coefficients have been evaluated. The apparent adsorption rate constant was k(298 K)=4.01 x 10(-5)s(-1), and the apparent activation energy was 2.78 kJ/mol. Thermodynamic parameters, DeltaS was 108 J/(mol K), heat of adsorption (Delta H) value of 12.8 kJ/mol indicated the endothermic nature of the adsorption process, and a decrease of Gibbs free energy (Delta G) with increasing temperature also indicated the spontaneous nature of the process, respectively. The elution tests were carried out using various mixed reagents. The maximum elution percent of cadmium(II) ions were obtained when the reagent 0.5 mol/L HCl was used.

Laser-based gene transfection and gene therapy

The plasma membrane of mammalian cells can be transiently permeablized by optical means and exogenous materials or genes can be introduced into the cytoplasm of living cells. Until now, few mechanisms were exploited for the manipulation: laser is directly and tightly focused on the cells for optoinjection, laser-induced stress waves, photochemical internalization, and irradiation of selective cell targeting with light-absorbing particles. During the past few years, extensive progress and numerous breakthroughs have been made in this area of research. This review covers four different laser-assisted transfection techniques and their advantages and disadvantages. Universality towards various cell lines is possibly the main advantage of laser-assisted optoporation in comparison with presently existing methods of cell transfection.

Methylmercury alters glutamate transport in astrocytes

Methylmercury (MeHg) is a significant environmental contaminant that will continue to pose great risk to human health. Considerable attention in the scientific and health policy fora is focused on the question of whether MeHg intake from a diet high in fish is associated with aberrant CNS function. A number of recent studies (Kjellstrom et al., 1986: Kjellstrom, T., Kennedy, P., Wallis, S., Mantell, C., 1986. Physical and mental development of children with prenatal exposure to mercury from fish. Stage I: preliminary tests at age 4. Solna, Sweden. National Swedish Environmental Protection Board Report 3080, 1989: Kjellstrom, T., Kennedy, P., Wallis, S., Stewart, A., Friberg, L. et al., 1989. Physical and mental development of children with prenatal exposure to mercury from fish. Stage II: interviews and psychological tests at age 6. Solna, Sweden. National Swedish Environmental Protection Board Report 3642; McKeown-Eyssen et al., 1983: McKeown-Eyssen, G., Ruedy, J., Neims, A. , 1983. Methylmercury exposure in Northern Quebec II: neurologic findings in children. American Journal of Epidemiology 118, 470-479; Grandjean et al., 1997: Grandjean, P., Weihe, P., White, R. F., Debes, F., Araki, S., Yokoyama, K., Murata, K., Sorensen, N., Dahl, R., Jorgensen, P. J., 1997. Cognitive deficit in 7-year-old children with prenatal exposure to methylmercury. Neurotoxicology and Teratology 19, 417-428) suggest that fetal exposure at levels attained by mothers eating fish regularly during pregnancy are associated with neurological deficits in their offspring. Astrocytes play a key role in MeHg-induced excitotoxicity. (1) MeHg preferentially accumulates in astrocytes. (2) MeHg potently and specifically inhibits glutamate uptake in astrocytes. (3) Neuronal dysfunction is secondary to disturbances in astrocytes. (4) Co-application of nontoxic concentrations of MeHg and glutamate leads to the typical appearance of neuronal lesions associated with excitotoxic stimulation. (5) MeHg induces swelling of astrocytes. These observations are fully consistent with MeHg-induced dysregulation of excitatory amino acid homeostasis, and indicate that a glutamate-mediated excitotoxic mechanism is involved. This manuscript details the role of astrocytes in mediating MeHg-induced excitotoxicity, and elaborates on the protective role afforded by metallothioneins (MTs) in attenuating MeHg cytotoxicity.

Metallothioneins attenuate methylmercury-induced neurotoxicity in cultured astrocytes and astrocytoma cells

Metallothionein-I (MT-I) was expressed in neonatal rat primary astrocyte cultures and an astrocytoma cell line by pGFAP-MT-I plasmid transfection under the control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. Following transient transfection of the pGFAP-MT-I plasmid, MT-I mRNA and MT-I protein levels were determined by Northern blot and immunoprecipitation analyses, respectively. The ability of cells overexpressing MT-I to withstand acute methylmercury (MeHg) treatment was measured by the release of preloaded Na2(51)CrO4, an indicator of membrane integrity. Transfection with the pGFAP-MT-I plasmid led to increased mRNA (2.5-fold in astrocytes and 7.4-fold in astrocytomas) and MT-I protein (2.4-fold in astrocytes and 4.0-fold in astrocytomas) levels compared with their respective controls. Increased expression of MT-I was associated with attenuated release of Na2(51)CrO4 upon MeHg (5 microM) treatment. These results demonstrate that MT-I can be highly expressed both in primary astrocyte cultures and astrocytomas by pGFAP-MT-I plasmid transfection, and lend credence to the hypothesis that increased expression of MT-I affords protection against the cytotoxic effects of MeHg. Taken together, the data suggest that MTs offer effective cellular adaptation of MeHg cytotoxicity.

Foreign metallothionein-I expression by transient transfection in MT-I and MT-II null astrocytes confers increased protection against acute methylmercury cytotoxicity

The mechanisms associated with metallothionein (MT) gene regulation are complex and poorly understood. Only a modest increase in brain MT expression levels is attained by exposure to metals, MT gene transfection, and MT gene knock-in techniques. Accordingly, in the present study, MT null astrocytes isolated from transgenic mice deficient in MT-I and MT-II genes were introduced as a zero background model of MT expression. MT protein levels were determined by western blot analysis. MT proteins in MT-I and MT-II null astrocytes were undetectable. Transient MT-I gene transfection increased the levels of foreign MT expression in MT-I and MT-II null astrocytes by 2.3-fold above basal levels in wild-type astrocytes. Intracellular Na(2)51CrO(4) efflux and D-[2,3-3H]aspartate uptake were studied as indices of acute methylmercury (MeHg) (5 microM) cytotoxicity. In MT-I and MT-II knockout astrocytes MeHg led to significant (p<0.01) increase in Na(2)51CrO(4) efflux and a significant (p<0.05) decrease in the initial rate (1 min) of D-[2, 3-3H]aspartate uptake compared to MT-I and MT-II knockout controls. Transfection of the MT-I gene in MT-I and MT-II null mice significantly (p<0.01) decreased the effect of MeHg on Na(2)51CrO(4) efflux in MT null, as well as wild-type astrocytes. MT-I gene transfection in MT-I and MT-II null astrocytes reversed the inhibitory effect of MeHg on D-[2,3-3H]aspartate uptake, such that initial rates of uptake in MT-I transfected cells in the presence and absence of MeHg (5 microM) were indistinguishable. These results demonstrate that: (1) astrocytes lacking MTs are more sensitive to MeHg than those with basal MT protein levels, (2) the MT-I gene can be overexpressed in MT-I and MT-II null astrocytes by transient MT-I gene transfection, and (3) that foreign MT expression endows astrocytes with increased resistance to MeHg.

Cytotoxicity induced by the combination of valproic acid and tumor necrosis factor-alpha: implication for valproic acid-associated hepatotoxicity syndrome

A previous study showed that valproic acid (VPA) and tumor necrosis factor-alpha (TNF-alpha) exhibit synergistic toxicity (lethality) in Sprague-Dawley and Wistar rats. The present study investigated a possible mechanism for this synergy using an in vitro system. Incubation of human U937 cells with 1 mM VPA or with 0.001 ng/mL of TNF-alpha alone had a negligible effect on cytotoxicity (less than 7%). However, the combination of the two drugs significantly increased the cytotoxicity up to 34%. Chronic treatment of U937 cells with VPA or TNF-alpha for 48 hr reduced protein kinase C (PKC) activity. Further, the PKC selective inhibitor Gö6976 potentiated VPA-induced cytotoxicity and TNF-alpha-induced cytotoxicity, whereas the PKC activator phorbol-12-myristate-13-acetate provided a significant protection against the cytotoxicity associated with VPA or TNF-alpha. These results suggest that the synergism in cytotoxicity exhibited by the combination of VPA and TNF-alpha may be mediated through attenuation of PKC activity.

Transfection and overexpression of metallothionein-I in neonatal rat primary astrocyte cultures and in astrocytoma cells increases their resistance to methylmercury-induced cytotoxicity

Metallothionein-I (MT-I) was expressed in neonatal rat primary astrocyte cultures and an astrocytoma cell line by pGFAP-MT-I plasmid transfection under the control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. Following transient transfection of the pGFAP-MT-I plasmid, MT-I mRNA and MT-I protein levels were determined by northern blot and immunoprecipitation analyses, respectively. The ability of cells over-expressing MT-I to withstand acute methylmercury (MeHg) treatment was measured by the release of preloaded Na251CrO4, an indicator of membrane integrity. Transfection with the pGFAP-MT-I plasmid led to increased mRNA (2. 5-fold in astrocytes and 7.4-fold in astrocytomas) and MT-I protein (2.4-fold in astrocytes and 4.0-fold in astrocytomas) levels compared with their respective controls. Increased expression of MT-I was associated with attenuated release of Na251CrO4 upon MeHg (5 microM) treatment. These results demonstrate that MT-I can be highly expressed both in primary astrocyte cultures and astrocytomas by pGFAP-MT-I plasmid transfection, and lend credence to the hypothesis that increased expression of MT-I affords protection against the cytotoxic effects of MeHg. Taken together, the data suggest that MT offer effective cellular adaptation to MeHg cytotoxicity.

Induction of astrocyte metallothioneins (MTs) by zinc confers resistance against the acute cytotoxic effects of methylmercury on cell swelling, Na+ uptake, and K+ release

Metallothionein (MT) proteins play an important role in the detoxification of heavy metals. Since methylmercury (MeHg) preferentially accumulates in astrocytes, we investigated the ability of the astrocyte-specific MT isoform, MT-I, to attenuate MeHg-induced cytotoxicity. Increased astrocytic MT expression was achieved by 24-h pretreatment of neonatal rat primary astrocyte cultures with 100 microM zinc (ZnSO4). Subsequently, the astrocytes were treated with MeHg (10 microM), and its toxic effects on cell volume, Na+ uptake, and K+ release were investigated and compared to cells treated with or without MeHg, but in the absence of Zn pretreatment. Pretreatment of astrocytes with Zn was associated with a 2.9-fold increase in MT protein levels (P<0.02), and a 5.6-fold increase in MT mRNA levels (p<0.002) compared to control astrocytes. Astrocytes expressing increased MT protein levels were resistant to MeHg-induced swelling. In isotonic buffer the effect of MeHg on swelling was abolished (p<0.01) by 24-h Zn pretreatment, in such a way that volume profiles in these cells did not differ from controls. Zn-induced increased expression of MTs was also associated with significant attenuation of astrocytic Na+ uptake (p<0.01) and Rb+ (a marker for K+) release (p<0.001) in response to treatment with MeHg. These results demonstrate (1) that astrocytes can be induced to express high levels of MT proteins by pretreatment with Zn, and (2) that Zn confers resistance against the acute effect of MeHg on astrocytic swelling and the associated changes in ion (Na+ and K+) transport. Taken together, the data suggest that astrocytic MT induction offers effective cellular adaptation to MeHg cytotoxicity.

Modulation by calcium/calmodulin-dependent protein kinase II of functional response of delta opioid receptor in neuroblastoma x glioma hybrid (NG108-15) cells

The potential modulation of opioid receptor signaling by calcium/calmodulin-dependent protein kinase II (CaMKII) has been investigated in NG108-15 cells. Both CaMKII specific inhibitors used, KN62 and KN93, time- and dose-dependently blocked inhibition of cAMP accumulation by [D-Pen2, D-Pen5]enkephalin (DPDPE), with an IC50 of about 1.2 microM and 0.8 microM, respectively. In the presence of 1 microM KN62 or KN93, the DPDPE dose-response curve shifted to the right (IC50 from 0.7 to 20 nM for KN62 and from 0.65 to 10 nM for KN93, respectively), and the maximal response was also significantly reduced. KN92, an inactive analogue of KN93, showed no significant impact, while ionomycin, an activator of CaMKII, greatly potentiated the opioid receptor response, suggesting that the effects of KN62, KN93 and ionomycin were likely mediated through CaMKII. In addition, KN62 did not affect ligand binding, receptor/Gi coupling, or basal and forskolin-stimulated adenylyl cyclase activity, suggesting its possible interference in the Gi/adenylyl cyclase interaction. Furthermore, a CaMKII inhibitor potently blocked the functional responses of other Gi-coupled receptors (m4 muscarinic and alpha2 adrenergic receptors) tested, but not that of Gs-coupled receptors (prostaglandin E1 and adenosine receptors). Our results clearly demonstrate that CaMKII modulates the signaling of opioid receptor and other Gi-coupled receptors.