Abstract-Reactive oxygen species and proinflammatory cytokines contribute to cardiovascular diseases. Inhibition of downstream transcription factors and gene modifiers of these components are key mediators of hypertensive response. Histone acetylases/deacetylases can modulate the gene expression of these hypertrophic and hypertensive components. Therefore, we hypothesized that long-term inhibition of histone deacetylase with valproic acid might attenuate hypertrophic and hypertensive responses by modulating reactive oxygen species and proinflammatory cytokines in SHR rats. Seven-week-old SHR and WKY rats were used in this study. Following baseline blood pressure measurement, rats were administered valproic acid in drinking water (0.71% wt/vol) or vehicle, with pressure measured weekly thereafter. Another set of rats were treated with hydralazine (25 mg/kg per day orally) to determine the pressure-independent effects of HDAC inhibition on hypertension. Following 20 weeks of treatment, heart function was measured using echocardiography, rats were euthanized, and heart tissue was collected for measurement of total reactive oxygen species, as well as proinflammatory cytokine, cardiac hypertrophic, and oxidative stress gene and protein expressions. Blood pressure, proinflammatory cytokines, hypertrophic markers, and reactive oxygen species were increased in SHR versus WKY rats. These changes were decreased in valproic acid-treated SHR rats, whereas hydralazine treatment only reduced blood pressure. These data indicate that long-term histone deacetylase inhibition, independent of the blood pressure response, reduces hypertrophic, proinflammatory, and hypertensive responses by decreasing reactive oxygen species and angiotensin II type1 receptor expression in the heart, demonstrating the importance of uncontrolled histone deacetylase activity in hypertension. (Hypertension. 2010;56:437-444.)Key Words: Ang II Ⅲ cardiac hypertrophy Ⅲ cytokines Ⅲ hypertension Ⅲ oxidative stress Ⅲ HDAC E ssential hypertension is a condition associated with increased expression of proinflammatory cytokines (PICs). 1,2 Studies from our laboratory and others have shown that PICs lead to an increase in reactive oxygen species (ROS), which upregulates nuclear factor (NF)B activity, thus further increasing PIC and ROS transcription and amplifying their subsequent actions. [3][4][5] Along with renin-angiotensin system (RAS) components, PICs also activate hypertrophic mediators, which can result in cardiac hypertrophy and altered cardiac remodeling and function. 6,7 There are many triggers of hypertensive-induced inflammation resulting in both hypertrophic and hypertensive responses, many of which are through transcription factor NFB activation, ultimately resulting in alterations of gene transcription and perpetuation of the hypertensive state. 5,8 For transcription factors such as NFB to activate their target genes, DNA and chromatin remodeling must occur. Posttranslational modifications of histone cores through a tightly regulated addition/re...

AimsAngiotensin II (Ang II) has been shown to have both central and peripheral effects in mediating hypertension, for which the hypothalamic paraventricular nucleus (PVN) is an important brain cardio-regulatory centre. Angiotensin-converting enzyme 2 (ACE2) has been identified as a negative regulator of the pro-hypertensive actions of Ang II. Recent findings from our laboratory suggest that Ang II infusion decreases ACE2 expression in the PVN. In the present study, we hypothesized that ACE2 overexpression in the PVN will have beneficial effects in counteracting Ang II-induced hypertension. Methods and resultsMale Sprague-Dawley rats were used in this study. Bilateral microinjection of an adenovirus encoding hACE2 (Ad-ACE2) into the PVN was used to overexpress ACE2 within this region. Mean arterial pressure measured by radiotelemetry was significantly increased after 14 days in Ang II-infused (200 ng/kg/min) rats vs. saline-infused controls (162.9 + 3.6 vs. 102.3 + 1.5 mmHg). Bilateral PVN microinjection of Ad-ACE2 attenuated this Ang II-induced hypertension (130.2 + 5.7 vs. 162.9 + 3.6 mmHg). ACE2 overexpression also significantly decreased AT 1 R and ACE expression and increased AT 2 R and Mas expression in the PVN. Additionally, ACE2 overexpression in the PVN attenuated the Ang II-induced increase in the expression of the pro-inflammatory cytokines tumour necrosis factor-a, interleukin (IL)-1b and IL-6 in the PVN. ConclusionOur findings suggest that attenuation of pro-inflammatory cytokines in the PVN in combination with the shift of the renin -angiotensin system towards the anti-hypertensive axis (ACE2/Ang-(1-7)/Mas) may be responsible for the overall beneficial effects of ACE2 overexpression in the PVN on the Ang II-induced hypertensive response.---

Hypertension is considered a low-grade inflammatory condition and understanding the role of transcription factors in guiding this response is pertinent. A prominent transcription factor that governs inflammatory responses and has become a focal point in hypertensive research is Nuclear Factor-kappaB (NFκB). Within the hypothalamic paraventricular nucleus (PVN), a known brain cardio-regulatory center, NFκB becomes potentially even more important in ultimately coordinating the systemic hypertensive response. To definitively demonstrate the role of NFκB in the neurogenic hypertensive response, we hypothesized that PVN NFκB blockade would attenuate angiotensin II (AngII)-induced hypertension. Twelve-week old Sprague-Dawley rats were implanted with radio-telemetry probes for blood pressure measurement and allowed a 7-day recovery. Following baseline blood pressure recordings, rats were administered either continuous NFκB decoy oligodeoxynucleotide infusion or microinjection of a serine mutated Adenoviral Inhibitory-kappaB (AdIκB) vector, or their respective controls, bilaterally into the PVN to inhibit NFκB at two levels of its activation pathway. Simultaneously, rats were implanted subcutaneously with an AngII or saline-filled 14-day osmotic minipump. Following the 2-week treatments, rats were sacrificed and brain tissues collected for PVN analysis. Bilaterally inhibited NFκB rats had a decreased blood pressure, NFκB p65 subunit activity, proinflammatory cytokines and reactive oxygen species, including the AngII type-1 receptor, ACE, TNF and superoxide, in AngII-treated rats. Moreover, following NFκB blockade, key protective anti-hypertensive renin-angiotensin system components were up-regulated. This demonstrates the important role that transcription factor NFκB plays within the PVN in modulating and perpetuating the hypertensive response via renin-angiotensin system modulation.

Dysfunction of brain renin-angiotensin system (RAS) components is implicated in the development of hypertension. We previously showed that angiotensin (Ang) II-induced hypertension is mediated by increased production of proinflammatory cytokines (PIC), including tumor necrosis factor (TNF), in brain cardiovascular regulatory centers such as the paraventricular nucleus (PVN). Presently, we tested the hypothesis that central TNF blockade prevents dysregulation of brain RAS components and attenuates Ang II-induced hypertension. Male Sprague-Dawley rats were implanted with radio-telemetry transmitters to measure mean arterial pressure (MAP) and subjected to intracerebroventricular (ICV) infusion of etanercept (10 µg/kg/day) with/without concurrent subcutaneous 4-week Ang II (200 ng/kg/min) infusion. Chronic Ang II infusion resulted in a significant increase in MAP and cardiac hypertrophy, which was attenuated by inhibition of brain TNF with etanercept. Etanercept treatment also attenuated Ang II-induced increases in PIC and decreases in IL-10 expression in the PVN. Additionally, Ang II infusion increased expression of pro-hypertensive RAS components (ACE and AT1R), while decreasing anti-hypertensive RAS components (ACE2, Mas, and AT2 receptors), within the PVN. ICV etanercept treatment reversed these changes. Ang II-infusion was associated with increased oxidative stress as indicated by increased NAD(P)H oxidase activity and super oxide production in the PVN, which was prevented by inhibition of TNF. Moreover, brain targeted TNF blockade significantly reduced Ang II-induced NOX-2 and NOX-4 mRNA and protein expression in the PVN. These findings suggest that chronic TNF blockade in the brain protects rats against Ang II-dependent hypertension and cardiac hypertrophy by restoring the balance between pro- and anti-hypertensive RAS axes and inhibiting PIC and oxidative stress genes and proteins in the PVN.

Aims Findings from our laboratory indicate that proinflammatory cytokines and their transcription factor, nuclear factor-kappaB (NF-κB), are increased in the hypothalamic paraventricular nucleus (PVN) and contribute towards the progression of heart failure. In this study, we determined whether NF-κB activation within the PVN contributes to sympathoexcitation via interaction with neurotransmitters in the PVN during the pathogenesis of heart failure. Methods and results Heart failure was induced in rats by left anterior descending coronary artery ligation. Sham-operated control (SHAM) or heart failure rats were treated for 4 weeks through bilateral PVN infusion with SN50, SN50M or vehicle via osmotic minipump. Rats with heart failure treated with PVN vehicle or SN50M (inactive peptide for SN50) had increased levels of glutamate, norepinephrine, tyrosine hydroxylase (TH), superoxide, gp91phox (a subunit of NAD(P)H oxidase), phosphorylated IKKβ and NF-κB p65 activity, and lower levels of gamma-aminobutyric acid (GABA) and the 67-kDa isoform of glutamate decarboxylase (GAD67) in the PVN compared with those of SHAM rats. Plasma levels of cytokines, norepinephrine, epinephrine and angiotensin II, and renal sympathetic nerve activity (RSNA) were increased in heart failure rats. Bilateral PVN infusion of SN50 prevented, the decreases in PVN GABA and GAD67, and the increases in RSNA and PVN glutamate, norepinephrine, TH, superoxide, gp91phox, phosphorylated IKKβ and NF-κB p65 activity observed in vehicle or SN50M treated heart failure rats. A same dose of SN50 given intraperitoneally did not affect neurotransmitters concentration in the PVN and was similar to vehicle treated heart failure rats. Conclusion These findings suggest that NF-κB activation in the PVN modulates neurotransmitters and contributes to sympathoexcitation in rats with ischemia-induced heart failure.