Modification of cardiac disease by transgenically altered histone deacetylase 6.

Histone deacetylase 6 (HDAC6) is known to deacetylate amino acid lysine in alpha-tubulin. However, the functional role of HDAC6 in the progression of cardiac disease remains uncertain. The functional role of HDAC6 in the hearts was examined using transgenic (TG) mice expressing either human wild-type HDAC6, deacetylase inactive HDAC6 (HDAC6H216A, H611A), and human HDAC6 replaced all serine or threonine residues with aspartic acid at N-terminal 1- 43 amino acids (HDAC6NT-allD) specifically in the hearts. Overexpression of wild-type HDAC6 significantly reduced acetylated tubulin levels, and overexpression of HDAC6H216A, H611A significantly increased it in the mouse hearts. Detectable acetylated tubulin disappeared in HDAC6NT-allD TG mouse hearts. Neither histological alteration nor alteration of cardiac function was observed in the HDAC6 TG mouse hearts. To analyze the role of HDAC6 and acetylated tubulin in disease conditions, we examined HDAC6 in isoprenaline-induced hypertrophy or pressure-overload hypertrophy (TAC). No obvious alteration in the heart weight/body weight ratio or gene expressions of hypertrophic markers between NTG and HDAC6NT-allD mice was observed following treatment with isoprenaline. In contrast, a marked reduction in the shortening fraction and dilated chamber dilatation was detected in the HDAC6NT-allD TG mouse hearts 2 weeks after TAC. A sustained low level of acetylated tubulin and acetylated cortactin was observed in the TAC HDAC6NT-allD TG mouse hearts. Cardiac HDAC6 activity that can regulate acetylated levels of tubulin and cortactin may be critical factors involved in cardiac disease such as pressure-overload hypertrophy.

Bcl-2-associated athanogene 3 (BAG3) is an enhancer of small heat shock protein turnover via activation of autophagy in the heart.

Bcl-2-associated athanogene 3 (BAG3) is strongly expressed in both cardiac and skeletal muscle. A recent study showed that BAG3 may play a protective role in muscles. Little is known, however, regarding the detailed role of BAG3 in cardiac muscle. To better understand the functional role of cardiac BAG3 in the heart, we generated transgenic (TG) mice that overexpress BAG3. A decrease in fractional shortening, and the induction of cardiac atrial natriuretic peptide, were observed in BAG3 TG mice. Moreover, a marked reduction in the protein level of small HSPs was detected in BAG3 TG mouse hearts. We analyzed the cardiac small HSP levels when either the ubiquitin-proteasome system (UPS) or the autophagy system (AS) was inhibited in BAG3 TG mice. The protein turnovers of small HSPs by the AS were activated in BAG3 TG mouse hearts. Thus, BAG3 is critical for the protein turnover of small HSPs via activation of autophagy in the heart.

Effect of Geranylgeranylacetone on Ultraviolet Radiation Type B-Induced Cataract in Heat-Shock Transcription Factor 1 Heterozygous Mouse.

PURPOSE: We investigated whether heat-shock transcription factor 1 (HSF1) was involved in ultraviolet radiation type B (UVR-B)-induced lens opacity (cataract) using HSF1 heterozygous mice. We also examined the effects of geranylgeranylacetone (GGA), an inducer of heat-shock proteins via activation of HSF, on the UVR-B-induced cataract. MATERIAL AND METHODS: Male HSF1+/- and WT mice were unilaterally exposed to UVR-B (total: 1200mJ) at 16 weeks of age. At 48 h after the last UVR-B irradiation, the lens was isolated and the induction of the cataract was quantified as the cataract area ratio (opacity area/anterior capsule). GGA was orally administered at a dosage of 500 mg/kg once a day for two days before the first UVR-B exposure until the end of the experiment (21days in total). RESULTS: The HSF1 expression was more greatly decreased in the lens from HSF1+/- mice than in that from WT mice (p < 0.01). UVR-B exposure could mainly induce cataracts in the anterior capsule in both HSF1+/- and WT mice, while the opacity of the lens was markedly enhanced in HSF1+/- mice compared to that in WT mice(p (0.01). GGA treatment could prevent the induction of lens opacity by UVR-B exposure in both WT and HSF1+/- mice as compared with the non-administration group (p < 0.01). No obvious alteration by the UVR-B radiation was seen in lens protein levels of αA-crystallin, αB-crystallin, or γ-crystallin with or without GGA administration among all groups of mice. In contrast to the crystallins, the lens protein level of HSP25 was decreased by UVR-B exposure in both HSF1+/- and WT mice, and was significantly recovered in WT mice by the GGA treatment (p < 0.01). The induction of HSP25 was suppressed in HSF1+/- mice compared with that in WT mice. CONCLUSIONS: These data suggest that HSF1 plays an important role in the occurrence of UVR-B-induced cataracts, possibly via regulation of HSPs such as HSP25.

Upregulation of inorganic pyrophosphatase 1 as a JNK phosphatase in hypothyroid embryonic chick cerebellum.

AIM: Thyroid hormones play important roles in vertebrate neuronal development and differentiation. In our previous study, we showed that fetal thyroid dysfunction led to impaired social behaviors of hatchlings on post-hatch day 3, as well as to impaired learning and memory determined by the imprinting preference. However, little is known about the mechanisms underlying the direct adverse effects of fetal thyroid dysfunction on neuronal development. MATERIALS AND METHODS: We used a chick embryo as a fetal model to investigate the effects of prenatal exposure to antithyroid drugs on neuronal development in the chick cerebellum. Methimazole (MMI) at a dose of 20µmol/egg was administered to eggs on day 14, while the control was given only a vehicle. In order to address the underlying mechanisms of the impaired behavior, proteomic approaches were employed in the chick cerebellum two days after MMI treatment. KEY FINDINGS: In this experiment, we found that inorganic pyrophosphatase 1 (PPA1) was upregulated in the chick cerebellum treated with MMI, and we confirmed this upregulation of PPA1 by Western blot analysis as well as by RT-PCR analysis. Concomitant with the upregulation of PPA1, a marked reduction in JNK activity, as well as of phospho-JNK level, was detected in the MMI-treated chick cerebellum. SIGNIFICANCE: Since PPA1 can dephosphorylate JNK, these results suggest that the upregulation of PPA1 during neuronal development in the hypothyroid chick cerebellum may lead to impaired social behaviors as well as to impaired learning and memory via JNK dephosphorylation and inactivation in the chick cerebellum.