α-lipoic acid reduces hypertension and increases baroreflex sensitivity in renovascular hypertensive rats

Cardiovascular and Renal Effects Induced by Alpha-Lipoic Acid Treatment in Two-Kidney-One-Clip Hypertensive Rats

α-Lipoic acid (LA) is an antioxidant of endogenous production, also obtained exogenously. Oxidative stress is closely associated with hypertension, which causes kidney injury and endothelial dysfunction. Here, we evaluated the cardiovascular and renal effects of LA in the two-kidney-one-clip (2K1C) hypertension model. The rats were divided into four groups: Sham surgery (Sham), the two-kidneys-one-clip (2K1C) group, and groups treated with LA for 14 days (Sham-LA and 2K1C-LA). No changes were observed in the pattern of food, water intake, and urinary volume. The left/right kidney weight LKw/RKw ratio was significantly higher in 2K1C animals. LA treatment did not reverse the increase in cardiac mass. In relation to vascular reactivity, there was an increase in the potency of phenylephrine (PHE) curve in the hypertensive animals treated with LA compared to the 2K1C group and also compared to the Sham group. Vasorelaxation induced by acetylcholine (Ach) and sodium nitroprusside (SNP) were not improved by treatment with LA. Urea and creatinine levels were not altered by the LA treatment. In conclusion, the morphological changes in the aorta and heart were not reversed; however, the treatment with LA mitigated the contraction increase induced by the 2K1C hypertension.

Involvement of shedding induced by ADAM17 on the nitric oxide pathway in hypertension

A Disintegrin and Metalloprotease 17 (ADAM17), also called tumor necrosis factor-ɑ (TNF-ɑ) convertase (TACE), is a well-known protease involved in the sheddase of growth factors, chemokines and cytokines. ADAM17 is also enrolled in hypertension, especially by shedding of angiotensin converting enzyme type 2 (ACE2) leading to impairment of angiotensin 1–7 [Ang-(1–7)] production and injury in vasodilation, induction of renal damage and cardiac hypertrophy. Activation of Mas receptor (MasR) by binding of Ang-(1–7) induces an increase in the nitric oxide (NO) gaseous molecule, which is an essential factor of vascular homeostasis and blood pressure control. On the other hand, TNF-ɑ has demonstrated to stimulate a decrease in nitric oxide bioavailability, triggering a disrupt in endothelium-dependent vasorelaxation. In spite of the previous studies, little knowledge is available about the involvement of the metalloprotease 17 and the NO pathways. Here we will provide an overview of the role of ADAM17 and Its mechanisms implicated with the NO formation.

R- Is Superior to S-Form of α-Lipoic Acid in Anti-Inflammatory and Antioxidant Effects in Laying Hens

The development of single enantiomers with high efficiency and low toxic activity has become a hot spot for the development and application of drugs and active additives. The aim of the present study was to investigate the effectiveness of the application of α-lipoic acid with a different optical rotation to alleviate the inflammation response and oxidative stress induced by oxidized fish oil in laying hens. Sixty-four 124-week-old Peking Red laying hens were randomly allocated to four groups with eight replicates of two birds each. The normal group was fed basal diets supplemented with 1% fresh fish oil (FO), and the oxidative stress model group was constructed with diets supplemented with 1% oxidized fish oil (OFO). The two treatment groups were the S-form of the α-lipoic acid model with 1% oxidized fish oil (OFO + S-LA) and the R-form of the α-lipoic acid model with 1% oxidized fish oil (OFO + R-LA) added at 100 mg/kg, respectively. Herein, these results were evaluated by the breeding performance, immunoglobulin, immune response, estrogen secretion, antioxidant factors of the serum and oviduct, and pathological observation of the uterus part of the oviduct. From the results, diets supplemented with oxidized fish oil can be relatively successful in constructing a model of inflammation and oxidative stress. The OFO group significantly increased the levels of the serum inflammatory factor (TNF-α, IL-1β, IL-6, and IFN-γ) and the oxidative factor MDA and decreased the activity of the antioxidant enzyme (T-AOC, T-SOD, GSH-Px, GSH, and CAT) in the oviduct. The addition of both S-LA and R-LA significantly reduced the levels of serum inflammatory factors (TNF-α, IL-1β, IL-6, and IFN-γ), increased the activity of antioxidant indexes (T-AOC, T-SOD, GSH-Px, GSH, and CAT), and decreased the MDA contents in the serum and oviduct. Meanwhile, the supplementation of S-LA and R-LA also mitigated the negative effects of the OFO on the immunoglobulins (IgA and IgM) and serum hormone levels (P and E2). In addition, it was worth noting that the R-LA was significantly more effective than the S-LA in some inflammatory (IL-1β) and antioxidant indices (T-SOD, GSH, and CAT). Above all, both S-LA and R-LA can alleviate the inflammation and oxidative damage caused by oxidative stress in aged laying hens, and R-LA is more effective than S-LA. Thus, these findings will provide basic data for the potential development of α-lipoic acid as a chiral dietary additive for laying hens.

Effects of alpha lipoic acid on metabolic syndrome: A comprehensive review

Metabolic syndrome (MetS) is a multifactorial disease with medical conditions such as hypertension, diabetes, obesity, dyslipidemia, and insulin resistance. Alpha-lipoic acid (α-LA) possesses various pharmacological effects, including antidiabetic, antiobesity, hypotensive, and hypolipidemia actions. It exhibits reactive oxygen species scavenger properties against oxidation and age-related inflammation and refines MetS components. Also, α-LA activates the 5' adenosine monophosphate-activated protein kinase and inhibits the NFκb. It can decrease cholesterol biosynthesis, fatty acid β-oxidation, and vascular stiffness. α-LA decreases lipogenesis, cholesterol biosynthesis, low-density lipoprotein and very low-density lipoprotein levels, and atherosclerosis. Moreover, α-LA increases insulin secretion, glucose transport, and insulin sensitivity. These changes occur via PI3K/Akt activation. On the other hand, α-LA treats central obesity by increasing adiponectin levels and mitochondrial biogenesis and can reduce food intake mainly by SIRT1 stimulation. In this review, the most relevant articles have been discussed to determine the effects of α-LA on different components of MetS with a special focus on different molecular mechanisms behind these effects. This review exhibits the potential properties of α-LA in managing MetS; however, high-quality studies are needed to confirm the clinical efficacy of α-LA.

Naringin and Trimetazidine Improve Baroreflex Sensitivity and Nucleus Tractus Solitarius Electrical Activity in Renal Ischemia-Reperfusion Injury

BACKGROUND

Nucleus tractus solitarius (NTS) is a brain area that plays a key role in kidney and cardiovascular regulation via baroreceptors impulses.

OBJECTIVES

The aim of this study was to evaluate the effect of naringin (NAR) and trimetazidine (TMZ) alone and their combination on NTS electrical activity and baroreceptor sensitivity (BRS) in renal ischemia- reperfusion (I/R) injury.

METHODS

Forty male Sprague-Dawley rats (200- 250 g) were allocated into 5 groups with 8 in each. 1) Sham; 2) I/R; 3) TMZ 5 mg/kg; 4) NAR 100 mg/kg; and 5) TMZ5+ NAR100. The left femoral vein was cannulated to infuse saline solution or drug and the BRS was evaluated. I/R was induced by occlusion of renal pedicles for 45 min, followed by 4 hours of reperfusion. The NTS local electroencephalogram (EEG) was recorded before, during ischemia and throughout the reperfusion. Phenylephrine was injected intravenously to evaluate BRS at the end of reperfusion time. The data were analyzed by two-way repeated measurement ANOVA followed by Tukey's post hoc test. A p-value <0.05 was considered significant.

RESULTS

NTS electrical waves did not change during ischemia time, while they significantly decreased during the entire reperfusion time. NTS electrical activity and BRS dramatically reduced in rats with I/R injury; however, administration of NAR, TMZ alone or their combination significantly improved these changes in rats with I/R injury.

CONCLUSIONS

The results showed that I/R injury leads to reduced BRS and NTS electrical activity and there may be an association between I/R and decreased BRS. In addition, NAR and TMZ are promising agents to treat I/R complications.

Antioxidant Properties of Alpha-Lipoic (Thioctic) Acid Treatment on Renal and Heart Parenchyma in a Rat Model of Hypertension

Renal and cardiac impairments are frequent events in the presence of hypertension. Organ damage is mainly linked to oxidative stress due to high blood pressure and may be reduced by antioxidant supplementation. Alpha-lipoic acid (ALA) is one of most effective antioxidants. It is widely used as a nutritional supplement in a racemic mixture (+/–), even though the (+)-enantiomer is biologically active. This study was designed to investigate the effect of treatment with (+/–)-ALA and its enantiomers on renal and heart parenchyma in spontaneously hypertensive rats (SHR), using immunochemical and immunohistochemical techniques. The results confirmed that the oxidative mechanisms of organ alterations, due to hypertension, and characterized by glomerular and tubular lesions, left ventricular hypertrophy, and fibrosis but not by apoptosis were accompanied by proteins’ and nucleic acids’ oxidation. We found greater effectiveness of (+)-ALA compared to (+/−)-ALA in reducing oxidative stress, cardiac and renal damages in SHR. To conclude, these data propose (+)-ALA as one of the more appropriate antioxidant molecules to prevent renal and cardiac alterations associated with hypertension.

(r)Alpha Lipoic Acid Is a Safe, Effective Pharmacologic Therapy of Chronic Orthostatic Hypotension Associated with Low Sympathetic Tone

Chronic orthostatic hypotension (OH), affecting 10 to 30% of the elderly, is associated with falls, and increased morbidity and mortality. Current pharmacologic therapy can cause or worsen hypertension and fluid retention. (r)α lipoic acid (ALA), a powerful natural antioxidant, avoids those complications and may assist management of chronic neurogenic orthostatic hypotension (NOH). The purpose of this study is to demonstrate improvement in the symptoms of orthostatic dysfunction with r-ALA, including improved sympathetic (S) and blood pressure (BP) responses to head-up postural change (standing). A cohort of 109 patients with low S tone upon standing was detected using the ANX -3.0, Autonomic Monitor, ANSAR Medical Technologies, Inc., Philadelphia, PA. From the cohort, 29 patients demonstrated NOH (change in (∆) standing BP ≥ -20/-10 mm Hg); 60 patients demonstrated orthostatic intolerance (OI, ∆ standing systolic BP between -6 and -19 mm Hg). These 89 were given ALA orally: either 590 to 788 mg (r)ALA or 867 to 1,500 mg of the less expensive 50 to 50% mixture (r)ALA and inactive (s)ALA. Changes in their S and parasympathetic (P) tone, and BPs, were compared with 20 control patients during mean follow-up of 2.28 years. Nineteen of 29 (66%) NOH patients responded with a ∆ standing BP from -28/-6 mm Hg to 0/+2 mm Hg. Forty of 60 (67%) of patients with OI responded with a ∆ standing BP of -9/+1 mm Hg to +6/+2 mm Hg. Although all patients treated with ALA increased S tone, the ∆ BP depended upon the pretreatment of S tone. Those with the lowest S tone responded the least well. The only treatment side effects were nausea, intolerable in only 5%. Nausea improved with routine gastrointestinal medications. Glucose levels improved in the 28% of patients who were diabetic. Also, resting hypertension improved. Control patients had no ∆ BP and no increase in S tone. (r)ALA improves S-, and BP, responses to head-up postural change, and thereby NOH/OI, in a majority of patients without causing harmful side effects.

Central Inhibition of Tumor Necrosis Factor Alpha Reduces Hypertension by Attenuating Oxidative Stress in the Rostral Ventrolateral Medulla in Renovascular Hypertensive Rats

Inflammation in the central nervous system is being considered a key player linked to neurogenic hypertension. Using combined in vivo and in vitro approaches, we investigated the effects of central inhibition of TNF-α on blood pressure, sympathetic tone, baroreflex sensitivity, and oxidative stress in the rostral ventrolateral medulla (RVLM) of rats with 2-kidney-1-clip (2K1C) renovascular hypertension. Continuous infusion of pentoxifylline, a TNF-α inhibitor, into the lateral ventricle of the brain for 14 consecutive days reduced blood pressure and improved baroreflex sensitivity in renovascular hypertensive rats. Furthermore, central TNF-α inhibition reduced sympathetic modulation and blunted the increased superoxide accumulation in the RVLM of 2K1C rats. Our findings suggest that TNF-α play an important role in the maintenance of sympathetic vasomotor tone and increased oxidative stress in the RVLM during renovascular hypertension.

A Newly Isolated Carboxymethyl-Glucan (CM-G) Restores Depressed Baroreflex Sensitivity in Renovascular Hypertensive Rats

This study was designed to investigate the effects of a newly synthesized carboxymethyl-glucan (CM-G) on blood pressure (BP), baroreflex sensitivity (BRS) and sympathetic vascular modulation in renovascular hypertensive rats. Male Wistar rats were divided into four groups: Sham (n = 10); 2K1C (subjected to renal artery clipping to induce renovascular hypertension, n = 10); Sham + CM-G (treated with CM-G, n = 7) and 2K1C + CM-G (treated with CM-G, n = 7). The daily treatment with CM-G (40 mg/kg) was performed for 2 weeks. Blood pressure, heart rate (HR), systolic BP variability, baroreflex sensitivity (BRS) and sympathetic vascular tone were evaluated. After six weeks of renal artery clipping, 2K1C rats exhibited arterial hypertension (171 ± 11 vs. 118 ± 4 mmHg, p < 0.05), impaired BRS (-1.30 ± 0.10 vs. -2.59 ± 0.17 bpm.mmHg-1, p < 0.05) and enhanced sympathetic activity as shown by the hexamethonium test (-60 ± 5 vs. -33 ± 2 ΔmmHg, p < 0.05) when compared to sham rats. Oral administration of CM-G in renovascular hypertensive rats reduced hypertension (126 ± 4 vs. 171 ± 11 mmHg, p < 0.05) and improved the BRS (-2.03 ± 0.16 vs. -1.30 ± 0.10 bpm.mmHg^-1, p < 0.05) in 2K1C rats when compared to placebo. Those effects seem to be caused by a reduction in sympathetic activity. The present study revealed for the first time that CM-G treatment reduces arterial hypertension and restores arterial baroreflex sensitivity via a reduction in the sympathetic tone in conscious renovascular hypertensive rats.

Encapsulation of the Antioxidant R-(+)-α-Lipoic Acid in Permethylated α- and β-Cyclodextrins: Thermal and X-ray Structural Characterization of the 1:1 Inclusion Complexes

The naturally occurring compound α-lipoic acid (ALA) is implicated in manifold critical biological roles and its potent antioxidant properties and potential for treatment of various diseases have led to its widespread use as a dietary supplement. However, shortcomings of poor aqueous solubility and low thermal stability have hampered its development as a medicinal agent, prompting the use of cyclodextrins (CDs) to address these problems. The paucity of published structural data on the nature of the interactions between ALA and CDs motivated the present study, which describes the synthesis and X-ray structural elucidation of crystalline inclusion complexes between the biologically relevant R-(+)-α-lipoic acid (RALA) and the host molecules permethylated α-CD (TMA) and permethylated β-CD (TMB). Single crystal X-ray diffraction of TMA·RALA·6H₂O and TMB·RALA revealed significantly different orientations of the RALA molecule within the TMA and TMB cavities, but in both cases the guest molecule is fully encapsulated by the respective parent host molecules and residues of CD molecules of neighboring complex units. While pure RALA melted at 46-48 °C, combined thermal analysis techniques indicated that on heating the respective complexes, the release of RALA occurred at significantly higher onset temperatures, in the range 150-170 °C.

Inhibition of PDE5 Restores Depressed Baroreflex Sensitivity in Renovascular Hypertensive Rats

Renal artery stenosis is frequently associated with resistant hypertension, which is defined as failure to normalize blood pressure (BP) even when combined drugs are used. Inhibition of PDE5 by sildenafil has been shown to increase endothelial function and decrease blood pressure in experimental models. However, no available study evaluated the baroreflex sensitivity nor autonomic balance in renovascular hypertensive rats treated with sildenafil. In a translational medicine perspective, our hypothesis is that sildenafil could improve autonomic imbalance and baroreflex sensitivity, contributing to lower blood pressure. Renovascular hypertensive 2-kidney-1-clip (2K1C) and sham rats were treated with sildenafil (45 mg/Kg/day) during 7 days. At the end of treatment, BP and heart rate (HR) were recorded in conscious rats after a 24-h-recovery period. Spontaneous and drug-induced baroreflex sensitivity and autonomic tone were evaluated; in addition, lipid peroxidation was measured in plasma samples. Treatment was efficient in increasing both spontaneous and induced baroreflex sensitivity in treated hypertensive animals. Inhibition of PDE5 was also capable of ameliorating autonomic imbalance in 2K1C rats and decreasing systemic oxidative stress. Taken together, these beneficial effects resulted in significant reductions in BP without affecting HR. We suggest that sildenafil could be considered as a promising alternative to treat resistant hypertension.

Alpha lipoic acid supplementation attenuates reactive oxygen species in hypothalamic paraventricular nucleus and sympathoexcitation in high salt-induced hypertension

AIMS

High salt-induced oxidative stress plays an important role in the development of hypertension. Alpha lipoic acid (ALA) is extensively recognized as having a powerful superoxide inhibitory property. In this study, we determined whether ALA supplementation attenuates oxidative stress in hypothalamic paraventricular nucleus (PVN), decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by cross-talking with renin-angiotensin system (RAS) and pro-inflammatory cytokines (PICs).

METHODS

Male Wistar rats were administered a normal-salt diet (NS, 0.3% NaCl) or a high-salt diet (HS, 8.0% NaCl) for 8 weeks. These rats received ALA (60mg/kg) dissolved in vehicle (0.9% saline) or an equal voleme of vehicle, by gastric perfusion for 9 weeks.

RESULTS

High salt intake resulted in higher renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP). These rats also had higher levels of superoxide, gp91(phox), gp47(phox) (subunits of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), angiotensin II type1 receptor (AT1-R), interleukin-1beta (IL-1β), interleukin-6 (IL-6), and lower levels of interleukin-10 (IL-10) and copper/zinc superoxide dismutase (Cu/Zn-SOD) than control animals. Treatment with ALA significantly attenuated the levels of superoxide, gp91(phox), gp47(phox), ACE, AT1-R, IL-1β and IL-6, increased the levels of IL-10 and Cu/Zn-SOD, and decreased MAP and RSNA compared with high-salt induced hypertensive rats. The mRNA expression of gp47(phox) and gp91(phox) are in accordance with their protein expression.

CONCLUSION

These findings suggest that supplementation of ALA obviously decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by improving the superoxide inhibitory property, suppressing the activation of RAS and restoring the balance between pro- and anti-inflammatory cytokines in the PVN.

α-Lipoic acid reduces neurogenic hypertension by blunting oxidative stress-mediated increase in ADAM17

We previously reported that type 2 angiotensin-converting enzyme (ACE2) compensatory activity is impaired by the disintegrin and metalloprotease 17 (ADAM17), and lack of ACE2 is associated with oxidative stress in neurogenic hypertension. To investigate the relationship between ADAM17 and oxidative stress, Neuro2A cells were treated with ANG II (100 nM) 24 h after vehicle or α-lipoic acid (LA, 500 μM). ADAM17 expression was increased by ANG II (120.5 ± 9.1 vs. 100.2 ± 0.8%, P < 0.05) and decreased after LA (69.0 ± 0.3 vs. 120.5 ± 9.1%, P < 0.05). In another set of experiments, LA reduced ADAM17 (92.9 ± 5.3 vs. 100.0 ± 11.2%, P < 0.05) following its overexpression. Moreover, ADAM17 activity was reduced by LA in ADAM17-overexpressing cells [109.5 ± 19.8 vs. 158.0 ± 20.0 fluorescence units (FU)·min(-1)·μg protein(-1), P < 0.05], in which ADAM17 overexpression increased oxidative stress (114.1 ± 2.5 vs. 101.0 ± 1.0%, P < 0.05). Conversely, LA-treated cells attenuated ADAM17 overexpression-induced oxidative stress (76.0 ± 9.1 vs. 114.1 ± 2.5%, P < 0.05). In deoxycorticosterone acetate (DOCA)-salt hypertensive mice, a model in which ADAM17 expression and activity are increased, hypertension was blunted by pretreatment with LA (119.0 ± 2.4 vs. 131.4 ± 2.2 mmHg, P < 0.05). In addition, LA improved dysautonomia and baroreflex sensitivity. Furthermore, LA blunted the increase in NADPH oxidase subunit expression, as well as the increase in ADAM17 and decrease in ACE2 activity in the hypothalamus of DOCA-salt hypertensive mice. Taken together, these data suggest that LA might preserve ACE2 compensatory activity by breaking the feedforward cycle between ADAM17 and oxidative stress, resulting in a reduction of neurogenic hypertension.

Coconut oil supplementation and physical exercise improves baroreflex sensitivity and oxidative stress in hypertensive rats

The hypothesis that oral supplementation with virgin coconut oil (Cocos nucifera L.) and exercise training would improve impaired baroreflex sensitivity (BRS) and reduce oxidative stress in spontaneously hypertensive rats (SHR) was tested. Adult male SHR and Wistar Kyoto rats (WKY) were divided into 5 groups: WKY + saline (n = 8); SHR + saline (n = 8); SHR + coconut oil (2 mL·day(-1), n = 8); SHR + trained (n = 8); and SHR + trained + coconut oil (n = 8). Mean arterial pressure (MAP) was recorded and BRS was tested using phenylephrine (8 μg/kg, intravenous) and sodium nitroprusside (25 μg·kg(-1), intravenous). Oxidative stress was measured using dihydroethidium in heart and aorta. SHR + saline, SHR + coconut oil, and SHR + trained group showed higher MAP compared with WKY + saline (175 ± 6, 148 ± 6, 147 ± 7 vs. 113 ± 2 mm Hg; p < 0.05). SHR + coconut oil, SHR + trained group, and SHR + trained + coconut oil groups presented lower MAP compared with SHR + saline group (148 ± 6, 147 ± 7, 134 ± 8 vs. 175 ± 6 mm Hg; p < 0.05). Coconut oil combined with exercise training improved BRS in SHR compared with SHR + saline group (-2.47 ± 0.3 vs. -1.39 ± 0.09 beats·min(-1)·mm Hg(-1); p < 0.05). SHR + saline group showed higher superoxide levels when compared with WKY + saline (774 ± 31 vs. 634 ± 19 arbitrary units (AU), respectively; p < 0.05). SHR + trained + coconut oil group presented reduced oxidative stress compared with SHR + saline in heart (622 ± 16 vs. 774 ± 31 AU, p < 0.05). In aorta, coconut oil reduced oxidative stress in SHR compared with SHR + saline group (454 ± 33 vs. 689 ± 29 AU, p < 0.05). Oral supplementation with coconut oil combined with exercise training improved impaired BRS and reduced oxidative stress in SHR.

Alterations in the baroreceptor-heart rate reflex in conscious inbred polydipsic (STR/N) mice

STR/N is an inbred strain of mice which is known to exhibit extreme polydipsia and polyuria. We previously found central administration of angiotensin II enhanced cardiovascular responses in STR/N mice than normal mice, suggesting that STR/N mice might exhibit different cardiovascular responses. Therefore, in this study, we investigated daily mean arterial blood pressure and heart rate, and changes in the baroreceptor-heart rate reflex in conscious STR/N mice and control (ICR) mice. We found that variability in daily mean arterial blood pressure and heart rate was significantly larger in STR/N mice than in ICR mice (p<0.05). There was a stronger response to phenylephrine (PE) in STR/N mice than in ICR mice. For baroreceptor reflex sensitivity, in the rapid response period, the slopes of PE and sodium nitroprusside (SNP) were more negative in STR/N mice than in ICR mice. In the later period, the slopes of PE and SNP were negatively correlated between heart rate and blood pressure in ICR mice, but their slopes were positively correlated in STR/N mice. These results indicated that STR/N mice exhibited the different cardiovascular responses than ICR mice, suggesting that the dysfunction of baroreceptor reflex happened in conscious STR/N mice.

Calcium influx inhibition is involved in the hypotensive and vasorelaxant effects induced by yangambin

The pharmacological effects on the cardiovascular system of yangambin, a lignan isolated from Ocotea duckei Vattimo (Lauraceae), were studied in rats using combined functional and biochemical approaches. In non-anaesthetized rats, yangambin (1, 5, 10, 20, 30 mg/kg, i.v.) induced hypotension (−3.5 ± 0.2; −7.1 ± 0.8; −8.9 ± 1.3; −14 ± 2.3, −25.5% ± 2.6%, respectively) accompanied by tachycardia (5.9 ± 0.5; 5.9 ± 1.6; 8.8 ± 1.4; 11.6, 18.8% ± 3.4%, respectively). In isolated rat atria, yangambin (0.1 µM–1 mM) had very slight negative inotropic (Emax = 35.6% ± 6.4%) and chronotropic effects (Emax = 10.2% ± 2.9%). In endothelium-intact rat mesenteric artery, yangambin (0.1 µM–1 mM) induced concentration-dependent relaxation (pD₂ = 4.5 ± 0.06) of contractions induced by phenylephrine and this effect was not affected by removal of the endothelium. Interestingly, like nifedipine, the relaxant effect induced by yangambin was more potent on the contractile response induced by KCl 80 mM (pD₂ = 4.8 ± 0.05) when compared to that induced by phenylephrine. Furthermore, yangambin inhibited CaCl₂-induced contractions in a concentration-dependent manner. This lignan also induced relaxation (pD₂ = 4.0 ± 0.04) of isolated arteries pre-contracted with S(−)-Bay K 8644. In fura-2/AM-loaded myocytes of rat mesenteric arteries, yangambin inhibited the Ca²⁺ signal evoked by KCl 60 mM. In conclusion, these results suggest that the hypotensive effect of yangambin is probably due to a peripheral vasodilatation that involves, at least, the inhibition the Ca²⁺ influx through voltage-gated Ca²⁺ channels.

The effects of α-lipoic acid on aortic injury and hypertension in the rat remnant kidney (5/6 nephrectomy) model

Objective:

The present study was designed to investigate the effects of α-lipoic acid on the abdominal aorta and hypertension in a remnant kidney model histomorphometrically, immunohistochemically, and ultrastructurally.

Methods:

We surgically reduced the renal tissue mass to 5/6 by applying a remnant kidney model. The rats were divided into 4 groups: Group 1 control group, Group 2- lipoic acid group, Group 3- 5/6 nephrectomy group, and Group IV: 5/6 nephrectomy+lipoic acid-treated group. Lipoic acid solution 100 mg/kg was administered by oral gavage for 8 weeks to Groups II and IV. At the end of the experiment, systemic mean blood pressure was monitored. Then, aortic tissues were removed and fixed. After routine histological procedures, tissue sections were examined histochemically, immunohistochemically (type I angiotensin receptor, vascular endothelial growth factor, alpha-smooth muscle actin), and ultrastructurally.

Results:

The blood pressure measurements in 5/6 nephrectomy group were significantly higher compared to other groups. In the 5/6 nephrectomy+lipoic acid group, measured blood pressure values and tunica media thickness were significantly lower than in the 5/6 nephrectomy group. In the 5/6 nephrectomy+lipoic acid group, decreased aortic wall thickness, regularity in the structure of elastic fibrils, and more organized elastic lamellae were seen. The expression of type I angiotensin receptor, vascular endothelial growth factor, alpha-smooth muscle actin in the 5/6 nephrectomy+lipoic acid group was decreased compared to the 5/6 nephrectomy group.

Conclusion:

In the present study, we found that α-lipoic acid could be a favorable agent for the target organ effects of secondary hypertension.

Plasma membranes as heat stress sensors: from lipid-controlled molecular switches to therapeutic applications

The classic heat shock (stress) response (HSR) was originally attributed to protein denaturation. However, heat shock protein (Hsp) induction occurs in many circumstances where no protein denaturation is observed. Recently considerable evidence has been accumulated to the favor of the "Membrane Sensor Hypothesis" which predicts that the level of Hsps can be changed as a result of alterations to the plasma membrane. This is especially pertinent to mild heat shock, such as occurs in fever. In this condition the sensitivity of many transient receptor potential (TRP) channels is particularly notable. Small temperature stresses can modulate TRP gating significantly and this is influenced by lipids. In addition, stress hormones often modify plasma membrane structure and function and thus initiate a cascade of events, which may affect HSR. The major transactivator heat shock factor-1 integrates the signals originating from the plasma membrane and orchestrates the expression of individual heat shock genes. We describe how these observations can be tested at the molecular level, for example, with the use of membrane perturbers and through computational calculations. An important fact which now starts to be addressed is that membranes are not homogeneous nor do all cells react identically. Lipidomics and cell profiling are beginning to address the above two points. Finally, we observe that a deregulated HSR is found in a large number of important diseases where more detailed knowledge of the molecular mechanisms involved may offer timely opportunities for clinical interventions and new, innovative drug treatments. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.

Vascular dysfunction and chronic obstructive pulmonary disease: the role of redox balance

Chronic obstructive pulmonary disease (COPD) is characterized by low pulmonary function, inflammation, free radical production, vascular dysfunction, and subsequently a greater incidence of cardiovascular disease. By administering an acute oral antioxidant cocktail to patients with COPD (n=30) and controls (n=30), we sought to determine the role of redox balance in the vascular dysfunction of these patients. Using a double-blind, randomized, placebo-controlled, crossover design, patients with COPD and controls were ingested placebo or the antioxidant cocktail (vitamin C, vitamin E, α-lipoic acid) after which brachial artery flow-mediated dilation and carotid-radial pulse wave velocity were assessed using ultrasound Doppler. The patients exhibited lower baseline antioxidant levels (vitamin C and superoxide dismutase activity) and higher levels of oxidative stress (thiobarbituic acid reactive species) in comparison with controls. The patients also displayed lower basal flow-mediated dilation (P<0.05), which was significantly improved with antioxidant cocktail (3.1±0.5 versus 4.7±0.6%; P<0.05; placebo versus antioxidant cocktail), but not controls (6.7±0.6 versus 6.9±0.7%; P>0.05; placebo versus antioxidant cocktail). The antioxidant cocktail also improved pulse wave velocity in patients with COPD (14±1 versus 11±1 m·s(-1); P<0.05; placebo versus antioxidant cocktail) while not affecting controls (11±2 versus 10±1 m·s(-1); P>0.05; placebo versus antioxidant). Patients with COPD exhibit vascular dysfunction, likely mediated by an altered redox balance, which can be acutely mitigated by an oral antioxidant. Therefore, free radically mediated vascular dysfunction may be an important mechanism contributing to this population's greater risk and incidence of cardiovascular disease.

Angiotensin-II-derived reactive oxygen species on baroreflex sensitivity during hypertension: new perspectives

Hypertension is a multifactorial disorder, which has been associated with the reduction in baroreflex sensitivity (BRS) and autonomic dysfunction. Several studies have revealed that increased reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase, following activation of type 1 receptor (AT₁R) by Angiotensin-(Ang) II, the main peptide of the Renin–Angiotensin–Aldosterone System (RAAS), is the central mechanism involved in Ang-II-derived hypertension. In the present review, we will discuss the role of Ang II and oxidative stress in hypertension, the relationship between the BRS and the genesis of hypertension and how the oxidative stress triggers baroreflex dysfunction in several models of hypertension. Finally, we will describe some novel therapeutic drugs for improving the BRS during hypertension.

Oral supplementation with the rutin improves cardiovagal baroreflex sensitivity and vascular reactivity in hypertensive rats

The hypothesis that oral supplementation with the flavonoid rutin improves baroreflex sensitivity and vascular reactivity in hypertensive (2-kidney-1-clip (2K1C)) rats was tested. Sixty-four rats were divided in 4 groups: sham + saline; sham + rutin; 2K1C + saline, and 2K1C + rutin. Six weeks after 2K1C surgery, the animals were treated with saline or rutin (40 mg·kg(-1)·day(-1)) by gavage for 7 days. Baroreflex sensitivity test using phenylephrine (8 μg·kg(-1), iv) and sodium nitroprusside (25 μg·kg(-1), iv), vascular reactivity, and thiobarbituric acid reactive substances assay were performed. Baroreflex sensitivity in hypertensive rats was impaired and compared with sham (-2.77 ± 0.15 vs. -1.53 ± 0.27 beats·min(-1)·mm Hg(-1); n = 8; p < 0.05). Oral supplementation with rutin restored baroreflex sensitivity in 2K1C rats (-2.40 ± 0.24 vs. -2.77 ± 0.15 beats·min(-1)·mm Hg(-1); n = 8; p > 0.05). Besides, hypertensive rats have greater contraction to phenylephrine (129.49% ± 4.46% vs. 99.50% ± 11.36%; n = 8; p < 0.05), which was restored by rutin (99.10% ± 1.77% vs. 99.50% ± 11.36%; n = 8; p > 0.05). Furthermore, vasorelaxation to acetylcholine was diminished in hypertensive rats (96.42% ± 2.80% vs. 119.35% ± 5.60%; n = 8; p < 0.05), which was also restored by rutin (117.55% ± 6.94% vs. 119.35% ± 5.60%; n = 8; p > 0.05). Finally, oxidative stress was greater in hypertensive rats (1.54 ± 0.12 vs. 0.53 ± 0.12 nmol MDA·mL(-1); n = 8; p < 0.05) and rutin supplementation significantly decreased oxidative stress in those animals (0.70 ± 0.13 vs. 1.54 ± 0.12 nmol MDA·mL(-1); n = 8; p < 0.05). We concluded that oral supplementation with rutin restores impaired baroreflex sensitivity and vascular reactivity in hypertensive rats by decreasing oxidative stress.