HDAC6 inhibition induces the failure of mouse early embryonic development

Histone acetyltransferases and histone deacetyl transferases play crucial role during oogenesis and early embryo development

Dynamic epigenetic regulation is critical for proper oogenesis and early embryo development. During oogenesis, fully grown germinal vesicle oocytes develop to mature Metaphase II oocytes which are ready for fertilization. Fertilized oocyte proliferates mitotically until blastocyst formation and the process is called early embryo development. Throughout oogenesis and early embryo development, spatio-temporal gene expression takes place, and this dynamic gene expression is controlled with the aid of epigenetics. Epigenetic means that gene expression can be altered without changing DNA itself. Epigenome is regulated through DNA methylation and histone modifications. While DNA methylation generally ends up with repression of gene expression, histone modifications can result in expression or repression depending on type of modification, type of histone protein and its specific residue. One of the modifications is histone acetylation which generally ends up with gene expression. Histone acetylation occurs through the addition of acetyl group onto amino terminal of the core histone proteins by histone acetyltransferases (HATs). Contrarily, histone deacetylation is associated with repression of gene expression, and it is catalyzed by histone deacetylases (HDACs). This review article focuses on what is known about alterations in the expression of HATs and HDACs and emphasizes importance of HATs and HDACs during oogenesis and early embryo development.

HDAC6 decreases H4K16 and α-tubulin acetylation during porcine oocyte maturation

HDAC6 is an essential factor in mouse oocyte maturation. However, the roles of HDAC6 in porcine oocyte maturation are still unclear. Therefore, we analyzed the roles of HDAC6 in porcine oocyte maturation by treatment with Tubastatin A (TubA) which is an HDAC6 inhibitor. Our results showed that treatment with 10 μg/ml TubA significantly decreased the rate of porcine oocyte maturation, but it did not influence the rate of germinal vesicle breakdown (GVBD). Then, we found that TubA treatment disrupted spindle organization by increasing the α-tubulin acetylation level during porcine oocyte maturation. Moreover, TubA treatment significantly increased H4K16 acetylation, which may compromise kinetochore and microtubule (K-MT) attachment during meiosis in porcine oocytes. We also analyzed the effects of TubA on meiosis-related (H3T3pho and H3S10pho) and transcription-related histone modifications (H3K4me3, H3K9me3 and H3K4ac) during porcine oocyte maturation. The results showed that TubA treatment increased H3S10pho and H3K4ac levels, but no influence was seen in H3T3pho, H3K4me3 and H3K9me3 levels in porcine oocytes. TubA treated oocytes also showed a compromised ability to develop after parthenogenetic activation. Finally, we found that HDAC6 exhibited higher mRNA levels and lower DNA methylation levels in porcine oocytes than it did in porcine embryonic fibroblasts (PEFs). These results indicate that the low level of DNA methylation in HDAC6 promoter ensures high expression. HDAC6 regulates the deacetylation of α-tubulin and H4K16, which promotes correct spindle organization and meiotic apparatus assembly during porcine oocyte maturation. This study illustrates a new pathway by which HDAC6 modulates mammalian oocyte maturation.

Advances in the Mechanistic Study of the Control of Oxidative Stress Injury by Modulating HDAC6 Activity

Oxidative stress is defined as an injury resulting from a disturbance in the dynamic equilibrium of the redox environment due to the overproduction of active/radical oxygen exceeding the antioxidative ability of the body. This is a key step in the development of various diseases. Oxidative stress is modulated by different factors and events, including the modification of histones, which are the cores of nucleosomes. Histone modification includes acetylation and deacetylation of certain amino acid residues; this process is catalyzed by different enzymes. Histone deacetylase 6 (HDAC6) is a unique deacetylating protease that also catalyzes the deacetylation of different nonhistone substrates to regulate various physiologic processes. The intimate relationship between HDAC6 and oxidative stress has been demonstrated by different studies. The present paper aims to summarize the data obtained from a mechanistic study of HDAC6 and oxidative stress to guide further investigations on mechanistic characterization and drug development.

Pharmacological inhibition of HDAC6 overcomes cisplatin chemoresistance by targeting cancer stem cells in oral squamous cell carcinoma

BACKGROUND

Chemoresistance is associated with recurrence and metastasis in oral squamous cell carcinoma (OSCC). The cancer stem cell (CSC) subpopulation is highly resistant to therapy, and they are regulated by epigenetic mechanisms. HDACs are histone deacetylase enzymes that epigenetically regulate gene expression. HDAC6 acts on several physiological processes, including oxidative stress, autophagy and DNA damage response, and its accumulation is associated with cancer. Here, we investigate the role of HDAC6 in CSC-mediated chemoresistance in oral carcinoma in addition to its application as a therapeutic target to reverse chemoresistance.

METHODS

Wild-type oral carcinoma cell lines (CAL27 WT and SCC9 WT), cisplatin-resistant (CAL27 CisR and SCC9 CisR), and the subpopulations of cancer stem cells (CSC+) and non-stem (CSC-) derived from CisR cells were investigated. HDAC6 accumulation was analyzed by Western blot and immunofluorescence; DNA damage was evaluated by immunofluorescence of phospho-H2A.X; the qPCR for PRDX2, PRDX6, SOD2, and TXN and ROS assay assessed oxidative stress. Apoptosis and CSC accumulation were investigated by flow cytometry.

RESULTS

We identified the accumulation of HDAC6 in CisR cell lines and CSC. Cisplatin-resistant cell lines and CSC demonstrated a reduction in DNA damage and ROS and elevated expression of PRDX2. The administration of tubastatin A (a specific HDAC6 inhibitor) increased oxidative stress and DNA damage and decreased PRDX2. Tubastatin A as a monotherapy induced apoptosis in CisR and CSC and reduced the stemness phenotype.

CONCLUSION

High levels of HDAC6 sustain CSC subpopulation and chemoresistance in OSCC, suggesting HDAC6 as a pharmacological target to overcome resistance and perhaps prevent recurrence in OSCC.

Downregulation of HDAC8 expression decreases CD163 levels and promotes the apoptosis of macrophages by activating the ERK signaling pathway in recurrent spontaneous miscarriage

Recurrent spontaneous miscarriage (RSM) is a systemic disorder that has been defined as two or more pregnancies lost before the 20th week of gestation. Although the impaired function of macrophages at the maternal-fetal interface has been reported to be associated with RSM, the underlying mechanisms have not been fully elucidated. Here, we revealed that HDAC8 plays a critical role in RSM. Our results show that the mRNA and protein expression of HDAC8 was decreased in decidual macrophages from RSM patients. Moreover, the knockdown of HDAC8 resulted in a significant decrease in CD163 expression and an increase in apoptosis in dTHP-1 macrophages. Mechanistically, the ERK signaling pathway was activated in HDAC8-knockdown macrophages. When HDAC8-knockdown cells were pretreated with the ERK inhibitor U0126, expression levels of CD163, activated caspases 3, 7 and 9, and the apoptosis rate, were rescued. Taken together, our current results suggest that HDAC8 plays an important role in macrophage activation and apoptosis and may contribute to maintaining normal pregnancy by increasing the expression of M2 marker genes and inhibiting the apoptosis of macrophages at the maternal-fetal interface.

Role of HDAC6 inhibition in sepsis-induced acute respiratory distress syndrome (Review)

Acute respiratory distress syndrome (ARDS) induced by sepsis contributes remarkably to the high mortality rate observed in intensive care units, largely due to a lack of effective drug therapies. Histone deacetylase 6 (HDAC6) is a class-IIb deacetylase that modulates non-nuclear protein functions via deacetylation and ubiquitination. Importantly, HDAC6 has been shown to exert anti-cancer, anti-neurodegeneration, and immunological effects, and several HDAC6 inhibitors have now entered clinical trials. It has also been recently shown to modulate inflammation, and HDAC6 inhibition has been demonstrated to markedly suppress experimental sepsis. The present review summarizes the role of HDAC6 in sepsis-induced inflammation and endothelial barrier dysfunction in recent years. It is proposed that HDAC6 inhibition predominantly ameliorates sepsis-induced ARDS by directly attenuating inflammation, which modulates the innate and adaptive immunity, transcription of pro-inflammatory genes, and protects endothelial barrier function. HDAC6 inhibition protects against sepsis-induced ARDS, thereby making HDAC6 a promising therapeutic target. However, HDAC inhibition may be associated with adverse effects on the embryo sac and oocyte, necessitating further studies.

MiR-22-3p inhibits fibrotic cataract through inactivation of HDAC6 and increase of α-tubulin acetylation

OBJECTIVES

Fibrotic cataract, including posterior capsule opacification (PCO) and anterior subcapsular cataract (ASC), renders millions of people visually impaired worldwide. However, the underlying mechanism remains poorly understood. Here, we report a miRNA-based regulatory pathway that controls pathological fibrosis of lens epithelium.

MATERIALS AND METHODS

Expression of miR-22-3p and histone deacetylase 6 (HDAC6) in normal and PCO patient samples were measured by qPCR. Human lens epithelial explants were treated with TGF-β2 in the presence or absence of miR-22-3p mimics or inhibitor. Cell proliferation was determined by MTS assay, and migration was tested by transwell assay. Expression of HDAC6 and EMT-related molecules were analysed by Western blot, qPCR and immunocytochemical experiments.

RESULTS

We identify miR-22-3p as a downregulated miRNA targeting HDAC6 in LECs during lens fibrosis and TGF-β2 treatment. Mechanistically, gain- and loss-of-function experiments in human LECs and lens epithelial explants reveal that miR-22-3p prevents proliferation, migration and TGF-β2 induced EMT of LECs via targeting HDAC6 and thereby promoting α-tubulin acetylation. Moreover, pharmacological targeting of HDAC6 deacetylase with Tubacin prevents fibrotic opaque formation through increasing α-tubulin acetylation under TGF-β2 stimulated conditions in both human lens epithelial explants and the whole rat lenses.

CONCLUSIONS

These findings suggest that miR-22-3p prevents lens fibrotic progression by targeting HDAC6 thereby promoting α-tubulin acetylation. The 'miR-22-HDAC6-α-tubulin (de)acetylation' signalling axis may be therapeutic targets for the treatment of fibrotic cataract.