Differences in Calcium Clearance at Inner Hair Cell Active Zones May Underlie the Difference in Susceptibility to Noise-Induced Cochlea Synaptopathy of C57BL/6J and CBA/CaJ Mice

Noise exposure of a short period at a moderate level can produce permanent cochlear synaptopathy without seeing lasting changes in audiometric threshold. However, due to the species differences in inner hair cell (IHC) calcium current that we have recently discovered, the susceptibility to noise exposure may vary, thereby impact outcomes of noise exposure. In this study, we investigate the consequences of noise exposure in the two commonly used animal models in hearing research, CBA/CaJ (CBA) and C57BL/6J (B6) mice, focusing on the functional changes of cochlear IHCs. In the CBA mice, moderate noise exposure resulted in a typical fully recovered audiometric threshold but a reduced wave I amplitude of auditory brainstem responses. In contrast, both auditory brainstem response threshold and wave I amplitude fully recovered in B6 mice at 2 weeks after noise exposure. Confocal microscopy observations found that ribbon synapses of IHCs recovered in B6 mice but not in CBA mice. To further characterize the molecular mechanism underlying these different phenotypes in synaptopathy, we compared the ratio of Bax/Bcl-2 with the expression of cytochrome-C and found increased activity in CBA mice after noise exposure. Under whole-cell patch clamped IHCs, we acquired two-photon calcium imaging around the active zone to evaluate the Ca2+ clearance rate and found that CBA mice have a slower calcium clearance rate. Our results indicated that excessive accumulation of calcium due to acoustic overexposure and slow clearance around the presynaptic ribbon might lead to disruption of calcium homeostasis, followed by mitochondrial dysfunction of IHCs that cause susceptibility of noise-induced cochlear synaptopathy in CBA mice.

Effect of 5-hydroxypyrimidine derivatives on tumor growth and cytokine concentration in blood serum of female CBA mice with cervical cancer (RSHM-5)

The effects of intraperitoneal administration of SNK-411 (2-isobutyl-4,6-dimethyl-5-hydroxypyrimidine) in a dose of 25 mg/kg (the total dose of 350 mg/kg) and SNK-578 (hydrochloride of 2-isobutyl-4,6-dimethyl-5- hydroxypyrimidine) in a dose of 10 mg/kg (the total dose of 140 mg/kg) on tumor growth and concentration of cytokines in the blood serum were studied in female CBA mice. Substances were administrated from the 2nd to 15th days of tumor development. Tumor growth inhibition (TGI) and serum cytokine level were studied on the 7th day after the end of compounds administration (21st day of tumor growth). In intact control group (n=10) median tumor mass was 1255 mg. TGI in the group of animals treated with SNK-411 was 47%; in the group of mice treated with SNK-578 TGI was 87%, tumor mass demonstrated 7.4-fold reduction. Serum concentrations of cytokines (IL-6, IL-10, IL-17A and IFN-γ) in tumor-bearing group of mice were higher versus the intact control group by 229%, 40%, 60% and 81%, respectively. Highly active SNK-578 decreased concentrations of prooncogenic IL-10, IL-17A and proinflammatory IL-6, by 61%, 70% and 29% as compared to tumor-bearing control group. SNK-411 decreased concentrations of prooncogenic IL-10 and IL-17A by 48% and 60%, respectively, and did not affect concentration of IL-6. Taking into consideration that IL-6 participates in autoimmune reactions, we can assume that the immune control is one of the crucial mechanisms of antitumor effect of SNK-578. All results are statistically significant.

Dendritic Cells Transfected with MHC Antigenic Determinants of CBA Mice Induce Antigen-Specific Tolerance in C57Bl/6 Mice

Background. Nonspecific immunosuppressive therapy for graft rejection and graft-versus-host disease (GVHD) is often accompanied by severe side effects such as opportunistic infections and cancers. Several approaches have been developed to suppress transplantation reactions using tolerogenic cells, including induction of FoxP3+ Tregs with antigen-loaded dendritic cells (DCs) and induction of CD4+IL-10+ cells with interleukin IL-10-producing DCs. Here, we assessed the effectiveness of both approaches in the suppression of graft rejection and GVHD. Methods. IL-10-producing DCs were generated by the transfection of DCs with DNA constructs encoding mouse IL-10. Antigen-loaded DCs from C57BL/6 mice were generated by transfection with DNA constructs encoding antigenic determinants from the H2 locus of CBA mice which differ from the homologous antigenic determinants of C57BL/6 mice. Results. We found that both IL-10-producing DCs and antigen-loaded immature DCs could suppress graft rejection and GVHD but through distinct nonspecific and antigen-specific mechanisms, respectively. Discussion. We provide data that the novel approach for DCs antigen loading using DNA constructs encoding distinct homologous determinants derived from major histocompatibility complex genes is effective in antigen-specific suppression of transplantation reactions. Such an approach eliminates the necessity of donor material use and may be useful in immunosuppressive therapy side effects prevention.

Expression of 1L-myo-Inositol -1-Phosphate Synthase (EC 5.5.1.4) is Deregulated in the Cerebellum of Curly Tail Mutant Mice

Previous research, defining spatial control of inositol phosphate biosynthesis in the developing brain of CBA (normal) and CT [curly tail (ct-CT) and straight tail (st-CT)] mutant mice implicated a role for 1l-myo-inositol 1-phosphate synthase (MIP) in normal functioning of the central nervous system. Biochemical research indicated that MIP enzymatic activity, conversion of glucose 6-phosphate into inositol phosphate, is highest in the cerebellum of ct-CT and lowest in st-CT, when compared to that of CBA mice. Here, we utilized microscopic and biochemical investigations to analyze and extend previous findings of MIP expression in the cerebellum. Results of this research indicated that MIP expression correlates, well, with its enzymatic activity in the cerebellum of CBA and CT mutant mice. Statistical analyses of fluorescent micrographs detected a significant difference in fluorescence intensity between MIP from ct-CT, st-CT, and CBA mice. These data support vital links between inositol phosphate biosynthesis, MIP expression, and normal functioning of the cerebellum. Moreover, published data, identifying significant behavioral differences in the CT mutant, as well as data linking motor and non-motor cerebellar functions to abnormal levels of inositol, support the conclusion that aspects of normal cerebellar functions require temporal and spatial control of inositol phosphate biosynthesis, MIP expression.