Hae-Ahm Lee

Histone Deacetylase Inhibition Attenuates Transcriptional Activity of Mineralocorticoid Receptor Through its Acetylation and Prevents Development of Hypertension

Rationale: Inhibition of histone deacetylases (HDACs) results in attenuated development of hypertension in deoxycorticosterone acetate–induced hypertensive rats and spontaneously hypertensive rats. However, the molecular mechanism remains elusive. Objective: We hypothesized that HDAC inhibition attenuates transcriptional activity of mineralocorticoid receptor (MR) through its acetylation and prevents development of hypertension in deoxycorticosterone acetate–induced hypertensive rats. Methods and Results: Expression of MR target genes was measured by quantitative real-time polymerase chain reaction. Recruitment of MR and RNA polymerase II on promoters of target genes was analyzed by chromatin immunoprecipitation assay. Live cell imaging was performed for visualization of nuclear translocation of MR. MR acetylation was determined by Western blot with anti-acetyl-lysine antibody after immunoprecipitation with anti-MR antibody. Transcriptional activity of MR was determined by luciferase assay. For establishment of a hyperaldosteronism animal, Sprague-Dawley rats underwent uninephrectomy and received subcutaneous injection of 40 mg/kg per week of deoxycorticosterone acetate and drinking water containing 1% NaCl. Treatment with a HDAC class I inhibitor resulted in reduced expression of MR target genes in accordance with reduced recruitment of MR and RNA polymerase II on promoters of target genes. HDAC inhibition promoted MR acetylation, leading to decreased transcriptional activity of MR. Knockdown or inhibition of HDAC3 resulted in reduced expression of MR target genes induced by mineralocorticoids. Conclusions: These results indicate that HDAC inhibition attenuates transcriptional activity of MR through its acetylation and prevents development of hypertension in deoxycorticosterone acetate–induced hypertensive rats.

Tissue-Specific Upregulation of Angiotensin-Converting Enzyme 1 in Spontaneously Hypertensive Rats Through Histone Code Modifications

The renin-angiotensin system has been implicated in the development of hypertension and damages several organs. The expressions of the components of a local renin-angiotensin system (RAS) in the hypertensive rats differ from those of the normotensive rats. We hypothesized that local tissue-specific upregulation of angiotensin-converting enzyme 1 (ACE1) in hypertension is caused by epigenetic changes. Adrenal gland, aorta, heart, kidney, liver, and lung tissues were excised from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Ace1 mRNA and protein expressions were measured by real-time PCR and Western blot, respectively. Promoter methylation was revealed by bisulfite sequencing. Histone modifications, such as histone 3 acetylation (H3Ac), fourth lysine trimethylation (H3K4me3), and ninth lysine dimethylation (H3K9me2), were quantified by chromatin immunoprecipitation (ChIP), followed by real-time PCR. The expressions and associations of chromatin remodeling genes were analyzed by real-time PCR and ChIP, respectively. Local tissues from SHRs showed higher expressions of Ace1 mRNA and protein than those from the WKY rats. Ace1 promoter was mostly unmethylated in all of the tissues from both strains. The Ace1 promoter regions of SHR tissues were more enriched with H3Ac and H3K4me3, except in the lungs. The adrenal glands, hearts, and kidneys of SHRs showed less enrichment with H3K9me2. Valsartan treatment in SHRs decreased local Ace1 mRNA and protein expressions, which were accompanied by higher H3K9me2, as well as less H3Ac and H3K4me3. In conclusion, ACE1 is upregulated in local tissues of SHRs via histone code modifications.

Expression of Na+-K+-2Cl− Cotransporter 1 Is Epigenetically Regulated During Postnatal Development of Hypertension

BACKGROUND The expression of Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1) is upregulated in spontaneously hypertensive rat (SHR). We investigated whether expression of NKCC1 is epigenetically regulated during postnatal development of hypertension. METHODS The mesenteric arteries from 5-, 10-, and 18-week-old Wistar-Kyoto rats (WKY) and SHRs were subjected to vascular contraction. We determined expression levels of Nkcc1 mRNA and protein, methylation status, and histone modification of Nkcc1 promoter, and DNA methyltransferase (DNMT) activity. RESULTS The inhibition of dose-response curves by bumetanide, an inhibitor of NKCC1, as well as the expression of Nkcc1 mRNA and protein was comparable between 5-week-old SHR and age-matched WKY, but greater in 18-week-old SHR than in age-matched WKY. Nkcc1 promoter in WKY was getting methylated with age whereas that in SHR mostly remained hypomethylated after development of hypertension. DNMT3B was highly associated with the promoter of WKY, whereas the CXXC finger protein 1 (Cfp1) was highly bound to the promoter of SHR. At the age of 18 weeks, the DNMT activity in aorta of WKY was about threefold higher than that of SHR. The transcription-activating histone code acetyl H3 was higher in SHR than in WKY, whereas suppressive histone code dimethyl H3K9 was greater in WKY than in SHR. CONCLUSION It is concluded that expression of NKCC1 is epigenetically upregulated during postnatal development of hypertension. Our data indicate that maintenance of hypomethylation in Nkcc1 promoter of SHR resulting from low DNMT activity plays an important role in the upregulation of NKCC1 during development of spontaneous hypertension.

Promoter hypomethylation upregulates Na+-K+-2Cl- cotransporter 1 in spontaneously hypertensive rats.

The Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1) is one of several transporters that have been implicated for development of hypertension since NKCC1 activity is elevated in hypertensive aorta and vascular contractions are inhibited by bumetanide, an inhibitor of NKCC1. We hypothesized that promoter hypomethylation upregulates the NKCC1 in spontaneously hypertensive rats (SHR). Thoracic aortae and mesenteric arteries were excised, cut into rings, mounted in organ baths and subjected to vascular contraction. The expression levels of nkcc1 mRNA and protein in aortae and heart tissues were measured by real-time PCR and Western blot, respectively. The methylation status of nkcc1 promoter region was analyzed by combined bisulfite restriction assay (COBRA) and bisulfite sequencing. Phenylephrine-induced vascular contraction in a dose-dependent manner, which was inhibited by bumetanide. The inhibition of dose-response curves by bumetanide was much greater in SHR than in Wistar Kyoto (WKY) normotensive rats. The expression levels of nkcc1 mRNA and of NKCC1 protein in aortae and heart tissues were higher in SHR than in WKY. Nkcc1 gene promoter was hypomethylated in aortae and heart than those of WKY. These results suggest that promoter hypomethylation upregulates the NKCC1 expression in aortae and heart of SHR.

Possible involvement of DNA methylation in NKCC1 gene expression during postnatal development and in response to ischemia

J. Neurochem. (2010) 114, 520–529.

Histone Deacetylase 3 and 4 Complex Stimulates the Transcriptional Activity of the Mineralocorticoid Receptor.

Histone deacetylases (HDACs) act as corepressors in gene transcription by altering the acetylation of histones, resulting in epigenetic gene silencing. We previously reported that HDAC3 acts as a coactivator of the mineralocorticoid receptor (MR). Although HDAC3 forms complexes with class II HDACs, their potential role in the transcriptional activity of MR is unclear. We hypothesized that HDAC4 of the class II family stimulates the transcriptional activity of MR. The expression of MR target genes was measured by quantitative real-time PCR. MR and RNA polymerase II recruitment to promoters of MR target genes was analyzed by chromatin immunoprecipitation. The association of MR with HDACs was investigated by co-immunoprecipitation. MR acetylation was determined with an anti-acetyl-lysine antibody after immunoprecipitation with an anti-MR antibody. Among the class II HDACs, HDAC4 interacted with both MR and HDAC3 after aldosterone stimulation. The nuclear translocation of HDAC4 was mediated by protein kinase A (PKA) and protein phosphatases (PP). The transcriptional activity of MR was significantly decreased by inhibitors of PKA (H89), PP1/2 (calyculin A), class I HDACs (MS-275), but not class II HDACs (MC1568). MR acetylation was increased by H89, calyculin A, and MS-275, but not by MC1568. Interaction between MR and HDAC3 was significantly decreased by H89, calyculin A, and HDAC4 siRNA. A non-genomic effect of MR via PKA and PP1/2 induced nuclear translocation of HDAC4 to facilitate the interaction between MR and HDAC3. Thus, we have uncovered a crucial role for a class II HDAC in the activation of MR-dependent transcription.

Upregulation of the Na(+)-K(+)-2Cl(-) cotransporter 1 via histone modification in the aortas of angiotensin II-induced hypertensive rats.

The Na+-K+-2Cl− cotransporter 1 (NKCC1) is upregulated in diverse models of hypertension. We hypothesized that NKCC1 is upregulated via histone modification in the aortas of angiotensin II (Ang II)-induced hypertensive rats. An osmotic mini-pump containing Ang II was implanted in the subcutaneous tissues of the backs of Sprague-Dawley (SD) rats for 7 days. The systolic blood pressure was recorded every day by the tail-cuff method. On days 3 and 7, the mesenteric arteries were excised, cut into rings, mounted in organ baths and subjected to vascular contraction. The levels of Nkcc1 mRNA and protein in the aortas were measured using real-time PCR and Western blotting, respectively. The histone modifications and recruited proteins at the Nkcc1 promoter were determined by chromatin immunoprecipitation. The inhibition of concentration-response curves to phenylephrine by bumetanide, an inhibitor of NKCCs, was greater in Ang II-infused rats than in sham-operated (sham) rats . The levels of Nkcc1 mRNA and protein in the aortas increased gradually as Ang II was infused into the rats. Acetylated histone H3 (H3Ac), an activating histone code, was increased but trimethylated histone H3 at lysine 27 (H3K27me3), a repressive histone code, was greatly decreased in Ang II-infused rats compared with sham. RNA polymerase II was recruited to the Nkcc1 promoter with increased KDM6b. We conclude that the NKCC1 is upregulated via histone modification in the aortas of Ang II-induced hypertensive rats. Thus, we suggest that this ion transporter is epigenetically upregulated by histone modification or DNA demethylation upon the development of hypertension.

Differential antiproliferation effect of 2′-benzoyloxycinnamaldehyde in K-ras-transformed cells via downregulation of thiol antioxidants

2′‐Benzoyloxycinnamaldehyde (BCA), one of the derivatives of 2′‐hydroxycinnamaldehyde (HCA) isolated from the bark of Cinnamomum cassia, induces apoptosis in human cancer cells. We found that BCA induces stronger antiproliferative effects in K‐ras‐transformed cells (RK3E‐ras) than in isogenic non‐transformed cells (RK3E). Treatment of RK3E‐ras with BCA resulted in increased ROS generation and depletion of intracellular glutathione, whereas BCA‐treated RK3E showed no significant increase in the ROS level with concurrent increase in intracellular glutathione (GSH). Thiol antioxidants recovered cell proliferation inhibition caused by BCA in both cell lines, while non‐thiol antioxidants failed to recover cell death. BCA decreased metallothionein (MT) expression in RK3E‐ras, while inducing remarkable MT expression in RK3E. The increase of intracellular GSH in RK3E is partially caused by differential induction of γ‐glutamylcysteine synthetase (γ‐GCS) due to BCA treatment. To evaluate the upstream pathway for differential expression of γ‐GCS and MT, we analyzed early DJ‐1 (PARK7) and NF‐E2 p45‐related factor 2 (Nrf2) changes after BCA treatment. In RK3E, DJ‐1 expression considerably increased for 3 h with concurrent induction of Nrf2, whereas in RK3E‐ras cells BCA decreased these protein levels. Based on these findings, it seems that the therapeutic selectivity of BCA in RK3E‐ras results from decreased thiol antioxidants via decreased DJ‐1 and Nrf2 expression. (Cancer Sci 2011; 102: 212–218)

Enrichment of (pro)renin receptor promoter with activating histone codes in the kidneys of spontaneously hypertensive rats

Background: The (pro)renin receptor [(P)RR] non-proteolytically, through conformational change, activates prorenin which can convert angiotensinogen to angiotensin I in addition to the classic conversion of angiotensinogen to angiotensin I by circulating renin. Since renal (P)RR is upregulated in hypertension and implicated in the pathogenesis of malignant hypertension, we hypothesized that (pro)renin receptor promoter is enriched with activating histone codes in the kidney of spontaneously hypertensive rats (SHR). Methods: The mRNA and protein expression levels were measured by real-time polymerase chain reaction (PCR) and western blot, respectively. The DNA methylation status of (P)RR promoter region was analyzed by bisulfite sequencing. The histone modifications were determined by chromatin immunoprecipitation followed by real-time PCR. Results: The (P)RR mRNA expression in the kidney was about six times greater in SHR than in Wistar–Kyoto (WKY) rats. The (P)RR promoter was little methylated in the kidneys of both WKY and SHR. Acetylated histone H3 (H3Ac) and di-methylated histone H3 at lysine 4 (H3K4me2), activating histone codes, were about 25 and three times higher in SHR than in WKY, respectively. On the other hand, di-methylated histone H3 at lysine 9 (H3K9me2), a suppressive histone code, was 50 times lower in SHR than in WKY. Conclusion: These results suggest that the (P)RR promoter is enriched with activating histone codes in the kidneys of SHR.

Forkhead box O3 plays a role in skeletal muscle atrophy through expression of E3 ubiquitin ligases Murf-1 and Atrogin-1 in Cushing's syndrome.

Cushings syndrome is caused by overproduction of the adrenocorticotropic hormone (ACTH), which stimulates the adrenal grand to make cortisol. Skeletal muscle wasting occurs in pathophysiological response to Cushings syndrome. The forkhead box (FOX) protein family has been implicated as a key regulator of muscle loss under conditions such as diabetes and sepsis. However, the mechanistic role of the FOXO family in ACTH-induced muscle atrophy is not understood. We hypothesized that FOXO3a plays a role in muscle atrophy through expression of the E3 ubiquitin ligases, muscle RING finger protein-1 (MuRF-1), and atrogin-1 in Cushings syndrome. For establishment of a Cushings syndrome animal model, Sprague-Dawley rats were implanted with osmotic minipumps containing ACTH (40 ng·kg-1·day-1). ACTH infusion significantly reduced muscle weight. In ACTH-infused rats, MuRF-1, atrogin-1, and FOXO3a were upregulated and the FOXO3a promoter was targeted by the glucocorticoid receptor (GR). Transcriptional activity and expression of FOXO3a were significantly decreased by the GR antagonist RU486. Treatment with RU486 reduced MuRF-1 and atrogin-1 expression in accordance with reduced enrichment of FOXO3a and Pol II on the promoters. Knockdown of FOXO3a prevented dexamethasone-induced MuRF-1 and atrogin-1 expression. These results indicate that FOXO3a plays a role in muscle atrophy through expression of MuRF-1 and atrogin-1 in Cushings syndrome.