Enhanced autophagic clearance of amyloid-βvia histone deacetylase 6-mediated V-ATPase assembly and lysosomal acidification protects against Alzheimer's disease in vitro and in vivo

Recent studies have suggested that abnormal acidification of lysosomes induces autophagic accumulation of amyloid-βin neurons,which is a key step in senile plaque formation.Therefore,resto ring normal lysosomal function and rebalancing lysosomal acidification in neurons in the brain may be a new treatment strategy for Alzheimer's disease.Microtubule acetylation/deacetylation plays a central role in lysosomal acidification.Here,we show that inhibiting the classic microtubule deacetylase histone deacetylase 6 with an histone deacetylase 6 shRNA or thehistone deacetylase 6 inhibitor valproic acid promoted lysosomal reacidification by modulating V-ATPase assembly in Alzheimer's disease.Fu rthermore,we found that treatment with valproic acid markedly enhanced autophagy.promoted clearance of amyloid-βaggregates,and ameliorated cognitive deficits in a mouse model of Alzheimer's disease.Our findings demonstrate a previously unknown neuroprotective mechanism in Alzheimer's disease,in which histone deacetylase 6 inhibition by valproic acid increases V-ATPase assembly and lysosomal acidification.

Histone deacetylase 6 delays motor neuron degeneration by ameliorating the autophagic flux defect in a transgenic mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis （ALS） is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons. Abnormal protein aggregation and impaired protein degradation are believed to contribute to the pathogenesis of this disease. Our previous studies showed that an autophagic flux defect is involved in motor neuron degeneration in the SOD1G93A mouse model of ALS. Histone deacetylase 6 （HDAC6） is a class II deacetylase that promotes autophagy by inducing the fusion of autophagosomes to lysosomes. In the present study, we showed that HDAC6 expression was decreased at the onset of disease and became extremely low at the late stage in ALS mice. Using lentivirus-HDAC6 gene injection, we found that HDAC6 overexpression prolonged the lifespan and delayed the motor neuron degeneration in ALS mice. Moreover, HDAC6 induced the formation of autolysosomes and accelerated the degradation of SOD1 protein aggregates in the motor neurons of ALS mice. Collectively, our results indicate that HDAC6 has neuroprotective effects in an animal model of ALS by improving the autophagic flux in motor neurons, and autophagosome-lysosome fusion might be a therapeutic target for ALS.

Nicotine inhibits histone deacetylase 6 activity and chaperone-dependent activation of the glucocorticoid receptor in A549 cells

Background Nicotine,a major component of tobacco,is the main cause of smoking addiction.It was found that asthmatic patients who smoke were insensitive to glucocorticoid treatment.In this paper,we investigated whether nicotine could inhibit histone deacetylase 6 activity （HDAC6） and chaperone-dependent activation of the glucocorticoid receptor （GR） in A549 cells.Furthermore,the expression level of heat shock protein 90 （HSP90） was determined.Methods Quantitative real-time polymerase chain reaction was used to detect the levels of RNA transcription,and Western blotting was applied to analyze the levels of protein expression of HDAC6,GR,and HSP90 in A549 cells.Moreover,the effects of dexamethasone and trichostatin A were observed in A549 cells.Results A549 cell proliferation was inhibited in the presence of nicotine,and the level of RNA and protein expression of HDAC6 and GR were down-regulated.Conclusions Nicotine could inhibit HDAC6 activity and chaperone-dependent activation of GR.This might be the main reason why asthmatic patients who smoke show insensitivity to the glucocorticoid treatment.

Microtubule-associated deacetylase HDAC6 promotes angiogenesis by regulating cell migration in an EB1-dependent manner

Angiogenesis,a process by which the preexisting blood vasculature gives rise to new capillary vessels,is associated with a variety of physiologic and pathologic conditions.However,the molecular mechanism underlying this important process remains poorly understood.Here we show that histone deacetylase 6(HDAC6),a microtubule-associated enzyme critical for cell motility,contributes to angiogenesis by regulating the polarization and migration of vascular endothelial cells.Inhibition of HDAC6 activity impairs the formation of new blood vessels in chick embryos and in angioreactors implanted in mice.The requirement for HDAC6 in angiogenesis is corroborated in vitro by analysis of endothelial tube formation and capillary sprouting.Our data further show that HDAC6 stimulates membrane ruffling at the leading edge to promote cell polarization.In addition,microtubule end binding protein 1(EB1)is important for HDAC6 to exert its activity towards the migration of endothelial cells and generation of capillary-like structures.These results thus identify HDAC6 as a novel player in the angiogenic process and offer novel insights into the molecular mechanism governing endothelial cell migration and angiogenesis.

HDAC6 inhibitor loaded bimetallene nanosheets with antagonizing thermoresistance for augmented mild photothermal therapy

Photothermal therapy(PTT)induces thermoresistance through cellular heat shock response,which impairs the therapeutic efficacy of the PTT.To resolve this problem,we developed a photothermal theranostics(denoted as PMH),which integrated the photothermal conversion agent of PdMo bimetallene with histone deacetylase 6(HDAC6)selected inhibitor(ACY-1215),showing the synergistic antitumor effect both in vitro and in vivo.Mechanistically,under the photoacoustic imaging(PA)navigation,the released ACY-1215 triggered by NIR laser irradiation decrease the heat shock proteins(HSPs)expression and weaken the HDAC6-regulated HSP90 deacetylation,thus hindering the degradation of PTT-induced misfolded or unfold proteins through proteasome dependent pathway.Moreover,mild photothermal therapy(mPTT)treatment compromised the autophagy,which induced by HDAC6 inhibition,leading to mPTTinduced misfolded or unfold proteins further accumulation.Given that inhibition of HDAC6 plus m PTT contribute to tumor eradication.This study develops a promising combination strategy based on m PTT for future cancer treatment.

Design, Synthesis and Biological Evaluation of Novel Selective Thiol-based Histone Deacetylase（HDAC） Ⅵ Inhibitors Bearing Indeno[1,2-c]pyrazole or Benzoindazole Scaffold

A series of thiol-based mdeno[1,2-c]pyrazoles and benzoindazole compounds was designed and synthesized according to the structural specificity of his-tone deacetylase VI（HDAC6） and the structural characteristics of HDAC inhibitors. The inhibitory activities of the target compounds against HDAC6 and HDAC1 were screened by fluorescence analysis. Most of the target compounds showed moderate inhibitory activity against HDAC6（IC50=44-598 nmol/L）. Among them, compound A-4 displayed the highest selectivity against HDAC6 and similar inhibitory activity（IC50=44 nmol/L） to that of the positive drug SAHA（IC50=41 nmol/L） against HDAC6.