Calcium activated K⁺ channels in the electroreceptor of the skate confirmed by cloning. Details of subunits and splicing

Elasmobranchs detect small potentials using excitable cells of the ampulla of Lorenzini which have calcium-activated K(+) channels, first described in 1974. A distinctive feature of the outward current in voltage clamped ampullae is its apparent insensitivity to voltage. The sequence of a BK channel α isoform expressed in the ampulla of the skate was characterized. A signal peptide is present at the beginning of the gene. When compared to human isoform 1 (the canonical sequence), the largest difference was absence of a 59 amino acid region from the S8-S9 intra-cellular linker that contains the strex regulatory domain. The ampulla isoform was also compared with the isoform predicted in late skate embryos where strex was also absent. The BK voltage sensors were conserved in both skate isoforms. Differences between the skate and human BK channel included alternative splicing. Alternative splicing occurs at seven previously defined sites that are characteristic for BK channels in general and hair cells in particular. Skate BK sequences were highly similar to the Australian ghost shark and several other vertebrate species. Based on alignment of known BK sequences with the skate genome and transcriptome, there are at least two isoforms of Kcnma1α expressed in the skate. One of the β subunits (β4), which is known to decrease voltage sensitivity, was also identified in the skate genome and transcriptome and in the ampulla. These studies advance our knowledge of BK channels and suggest further studies in the ampulla and other excitable tissues.

Cardioprotective effects of fucoidan against hypoxia-induced apoptosis in H9c2 cardiomyoblast cells

CONTEXT

Cardiomyocyte apoptosis plays a critical role in the progress of heart diseases. Fucoidan, a complex-sulfated polysaccharide, has been reported to possess potential cardioprotective efficacy in vivo.

OBJECTIVE

The present study determines whether fucoidan could provide cardioprotection on hypoxia-induced cardiomyocyte apoptosis.

MATERIALS AND METHODS

H9c2 cardiomyoblast cells were incubated with various concentrations (15, 30, and 60 μg/ml) of fucoidan in a humidified incubator at 37 °C with 95% O2 and 5% CO2. After 6 h, hypoxia was processed and the cardioprotective effects of fucoidan were evaluated by applying MTT, ELISA, Hoechst 33258 nucleus staining, and western blot.

RESULTS

Following a 6 h exposure of H9c2 to hypoxic condition, significant reduction was found in cell survival (0.57-fold) and superoxide dismutase (SOD) activity (0.56-fold), which were associated with the increase of malondialdehyde (MDA) level (2.58-fold), creatine phosphokinase (CK, 3.57-fold), and lactate dehydrogenase (LDH) activities (2.39-fold). Moreover, hypoxia-induced apoptosis was confirmed by Hoechst 33258 nuclear staining, and these changes were accompanied by the increase of Bcl-2 (1.27-fold) and Bax expression (2.6-fold). However, preincubation of the cells with fucoidan prior to hypoxia exposure elevated the cell viability (30 μg/ml, 1.18-fold; 60 μg/ml, 1.32-fold) and SOD activity (30 μg/ml, 1.12-fold; 60 μg/ml, 1.25-fold), but decreased the MDA level (30 μg/ml, 0.70-fold; 60 μg/ml, 0.80-fold), CK (30 μg/ml, 0.69-fold; 60 μg/ml, 0.76-fold), and LDH (30 μg/ml, 0.67-fold; 60 μg/ml, 0.86-fold) leakages. Hoechst 33258 nuclear staining observations demonstrated the same protective effect of fucoidan on hypoxia-induced myocardial injury. Also, cardioprotective effects of fucoidan were reflected by increasing Bcl-2 (60 μg/ml, 1.84-fold), as well as decreasing Bax (60 μg/ml, 0.6-fold).

CONCLUSION

Fucoidan had protective effect against hypoxia-induced cardiomyocytes apoptosis, and the mechanism might involve protections of the cell from oxidative injury.

[Isolation and identification of two new secoiridoids of water-soluble chemical constituents from the fruits of Ligustrum lucidum Ait]

Two new secoiridoids named as specnuezhenide (I) and nuezhengalaside (II) were isolated from the water-soluble part of dry fruits of Ligustrum lucidum Ait. Their structures were established on the basis of chemical analysis and spectral data (UV, IR, 1H-NMR, NOEDS, HOMO-DEC, 13C-NMR, DEPT and MS).

Idiotype-specific T helper clones recognize a variable H chain determinant

Previously we described a Th clone specific for a regulatory idiotype on 3A4, an anti-Id mAb that mimics a murine L1210/GZL tumor-associated Ag. In our studies, we determined the molecular target on the stimulating anti-Id antibody that is recognized by the Th clone. The Th clone responds with proliferation to the H chain of 3A4 but not to the L chain. Furthermore, the 3A4 chain stimulates this Th clone more efficiently than either the intact 3A4 or the Fab fragments, and the presentation by APC of the H chain is more resistant to chloroquine treatment than the presentation of the intact 3A4 molecule. These results suggest that regulatory T cells "see" their target idiotopes as linear sequence determinants present on isolated Ig chains, and show that this might have biologic advantages with respect to the mechanism of Ag presentation.

Idiotype-specific T helper clones recognize a variable H chain determinant

Previously we described a Th clone specific for a regulatory idiotype on 3A4, an anti-Id mAb that mimics a murine L1210/GZL tumor-associated Ag. In our studies, we determined the molecular target on the stimulating anti-Id antibody that is recognized by the Th clone. The Th clone responds with proliferation to the H chain of 3A4 but not to the L chain. Furthermore, the 3A4 chain stimulates this Th clone more efficiently than either the intact 3A4 or the Fab fragments, and the presentation by APC of the H chain is more resistant to chloroquine treatment than the presentation of the intact 3A4 molecule. These results suggest that regulatory T cells "see" their target idiotopes as linear sequence determinants present on isolated Ig chains, and show that this might have biologic advantages with respect to the mechanism of Ag presentation.

Tumor idiotype vaccines. VI. Synergistic anti-tumor effects with combined "internal image" anti-idiotypes and chemotherapy

Anti-Id antibodies that have biologic activity as stimulators of specific immunity have been used in experimental vaccines and tumor protection models. However, very little is known about the therapeutic potential of anti-Id antibodies in animals and men. In this study we explored the combination of anti-Id and chemotherapy in a murine tumor system for which we had previously generated protective anti-Id mAb. First, we investigated various protocols by using a protective anti-Id in active immunization. Mice preimmunized before tumor transfer and challenged again after tumor survived significantly longer. Next, we explored the use of soluble anti-Id as immunostimulator in tumor-bearing mice. Although this treatment did not induce long-term survival, it significantly increased survival time. Interestingly, this anti-Id effect was dose dependent, whereby large and small doses had no effect. Finally, stimulatory anti-Id therapy and cyclophosphamide (Cy) treatment was combined. Tumor bearing mice were given a single dose of Cy followed by different doses of soluble anti-Id. The optimal effect on tumor growth and survival was achieved with 80 mg/kg Cy and 10 micrograms/mouse of anti-Id, where 80% of mice survived longer than 100 days. These results provide guidelines for developing clinical protocols for cancer patients by using combination therapy of anti-Id and chemotherapy.

Tumor idiotype vaccines. VI. Synergistic anti-tumor effects with combined "internal image" anti-idiotypes and chemotherapy

Anti-Id antibodies that have biologic activity as stimulators of specific immunity have been used in experimental vaccines and tumor protection models. However, very little is known about the therapeutic potential of anti-Id antibodies in animals and men. In this study we explored the combination of anti-Id and chemotherapy in a murine tumor system for which we had previously generated protective anti-Id mAb. First, we investigated various protocols by using a protective anti-Id in active immunization. Mice preimmunized before tumor transfer and challenged again after tumor survived significantly longer. Next, we explored the use of soluble anti-Id as immunostimulator in tumor-bearing mice. Although this treatment did not induce long-term survival, it significantly increased survival time. Interestingly, this anti-Id effect was dose dependent, whereby large and small doses had no effect. Finally, stimulatory anti-Id therapy and cyclophosphamide (Cy) treatment was combined. Tumor bearing mice were given a single dose of Cy followed by different doses of soluble anti-Id. The optimal effect on tumor growth and survival was achieved with 80 mg/kg Cy and 10 micrograms/mouse of anti-Id, where 80% of mice survived longer than 100 days. These results provide guidelines for developing clinical protocols for cancer patients by using combination therapy of anti-Id and chemotherapy.

Idiotypic intramolecular help. Induction of tumor-specific antibodies by monoclonal anti-idiotypic antibody with the help of Fc-specific T helper clones

In this study, the mechanism of anti-Id vaccination was investigated by using cloned Th cells and an anti-idiotypic mAb. 2F10, an anti-idiotypic mAb derived from an Igh1-e allotype mouse strain, which induces protection against the L1210/GZL DBA/2 tumor, was used to prime DBA/2 mice. An Fc (Igh1-e)-specific syngeneic Th clone was cocultured in the presence of 2F10 anti-Id with 2F10-Fab-primed B cells. The Th clone responded with proliferation and also provided help for 2F10-Fab-primed B cells to produce antibodies that bind to L1210/GZL and not to P815 tumor cells. Intact 2F10 anti-Id was presented to Fc-specific Th cells by Fab (or Id) primed B cells more efficiently than the fragment mixture (Fab plus Fc) of 2F10 anti-Id, indicating that 2F10-Fab (or Id)-primed B cells capture 2F10 anti-Id through surface Ig receptors. Presenting B cells are sensitive to treatment with chloroquine and must come from H-2 matched mice, indicating that the Ag presentation by Fab-primed B cells to Fc-specific Th cells requires processing and is MHC restricted. Collectively these results outline a mechanism that may operate in anti-Id therapy of tumor-bearing animals by using tumor Ag mimicking anti-idiotypic antibodies. A similar mechanism could be effective in tumor patients immunized with xenogeneic anti-idiotypic antibodies operating under the "intra(Ag) molecular help."

Idiotypic intramolecular help. Induction of tumor-specific antibodies by monoclonal anti-idiotypic antibody with the help of Fc-specific T helper clones

In this study, the mechanism of anti-Id vaccination was investigated by using cloned Th cells and an anti-idiotypic mAb. 2F10, an anti-idiotypic mAb derived from an Igh1-e allotype mouse strain, which induces protection against the L1210/GZL DBA/2 tumor, was used to prime DBA/2 mice. An Fc (Igh1-e)-specific syngeneic Th clone was cocultured in the presence of 2F10 anti-Id with 2F10-Fab-primed B cells. The Th clone responded with proliferation and also provided help for 2F10-Fab-primed B cells to produce antibodies that bind to L1210/GZL and not to P815 tumor cells. Intact 2F10 anti-Id was presented to Fc-specific Th cells by Fab (or Id) primed B cells more efficiently than the fragment mixture (Fab plus Fc) of 2F10 anti-Id, indicating that 2F10-Fab (or Id)-primed B cells capture 2F10 anti-Id through surface Ig receptors. Presenting B cells are sensitive to treatment with chloroquine and must come from H-2 matched mice, indicating that the Ag presentation by Fab-primed B cells to Fc-specific Th cells requires processing and is MHC restricted. Collectively these results outline a mechanism that may operate in anti-Id therapy of tumor-bearing animals by using tumor Ag mimicking anti-idiotypic antibodies. A similar mechanism could be effective in tumor patients immunized with xenogeneic anti-idiotypic antibodies operating under the "intra(Ag) molecular help."

Characterization of "regulatory" idiotope-specific T cell clones to a monoclonal anti-idiotypic antibody mimicking a tumor-associated antigen (TAA)

As reported previously, 3A4 is a paratope-specific anti-idiotypic mAb and induces cellular and humoral anti-tumor-associated Ag (TAA) responses. In this study, the specificity, MHC restriction and Ag processing requirement of Th cell lines and clones were determined that recognize an idiotypic determinant (Id) on 3A4. The anti-Id-3A4 is part of a tumor-associated idiotypic network which is involved in the regulation of the immunity against the DBA/2 L1210/GZL tumor. These 3A4-Id-specific T cell clones are phenotypically Th cells and recognize Id in the context of MHC class II molecules under MHC restriction. Moreover, the recognition of Id by these T cell clones is chloroquine sensitive, suggesting that they recognize processed Id. However, the 3A4-Id-specific T cell clones respond only to 3A4 and not to TAA. Because these clones do not recognize TAA, their biologic role in antitumor immunity could be as regulatory T cells involved in the idiotypic network regulation.

Characterization of "regulatory" idiotope-specific T cell clones to a monoclonal anti-idiotypic antibody mimicking a tumor-associated antigen (TAA)

As reported previously, 3A4 is a paratope-specific anti-idiotypic mAb and induces cellular and humoral anti-tumor-associated Ag (TAA) responses. In this study, the specificity, MHC restriction and Ag processing requirement of Th cell lines and clones were determined that recognize an idiotypic determinant (Id) on 3A4. The anti-Id-3A4 is part of a tumor-associated idiotypic network which is involved in the regulation of the immunity against the DBA/2 L1210/GZL tumor. These 3A4-Id-specific T cell clones are phenotypically Th cells and recognize Id in the context of MHC class II molecules under MHC restriction. Moreover, the recognition of Id by these T cell clones is chloroquine sensitive, suggesting that they recognize processed Id. However, the 3A4-Id-specific T cell clones respond only to 3A4 and not to TAA. Because these clones do not recognize TAA, their biologic role in antitumor immunity could be as regulatory T cells involved in the idiotypic network regulation.