Priscila de Souza

Impaired vascular function in sepsis-surviving rats mediated by oxidative stress and Rho-Kinase pathway

We investigated long-lasting changes in endothelial and vascular function in adult rat survivors of severe sepsis induced by cecal ligation and puncture (CLP) model. For this, male Wistar rats (200–350 g) had their cecum punctured once (non-transfixing hole) with a 14-gauge needle. Performed in this way, a mortality rate around 30% was achieved in the first 72 h. The survivors, together with age-matched control rats (not subjected to CLP), were maintained in our holding room for 60 days (S60 group) and had the descending thoracic aorta processed for functional, histological, biochemical or molecular analyses. Endothelium-intact aortic rings obtained from sepsis-surviving S60 group displayed increased angiotensin II-induced contraction, accompanied by decreased activity of the endogenous superoxide dismutase, augmented reactive oxygen species generation, and increased levels of tyrosine nitration compared with vessels from control group. The superoxide scavengers superoxide dismutase and tempol, and the antioxidant apocynin, were able to avoid this enhanced contractility to angiotensin II in aortic rings from the S60 group. In addition, aortic rings from the S60 group presented reduced sensitivity to Y-27632, a Rho-kinase (ROCK) inhibitor. Immunoblot analyses revealed augmented RhoA and ROCK II, and high levels of phosphorylation of myosin phosphatase target subunit 1 in vessels from S60 rats. In conclusion, aortic rings from sepsis-surviving rats display endothelial dysfunction mediated by the increased production of reactive oxygen species, which in turn reduces the bioavailability of nitric oxide and increases the formation of peroxynitrite, and enhances RhoA-ROCK-mediated calcium sensitization, leading to augmented contractile responses to angiotensin II. Notably, this is the first study demonstrating long-term dysfunction in the vasculature of sepsis-surviving rats, which take place or remain beyond the acute septic insult.

Matrix metalloproteinase inhibitors prevent sepsis-induced refractoriness to vasoconstrictors in the cecal ligation and puncture model in rats.

Previous studies have shown that the loss of contractility in aortas from lipopolysaccharide (LPS)-treated rats is related to intracellular activation of matrix metalloproteinase (MMPs). However, the role of MMPs in the vascular refractoriness to vasoconstrictors has not been investigated in a model of polymicrobial sepsis. We evaluated the effects of the oral administration of the MMP inhibitors doxycycline or ONO-4817 in the in vitro vascular reactivity of aortic rings from rats subjected to the cecal ligation and puncture (CLP) model of sepsis. Both doxycycline and ONO-4817 did not change vascular responses in sham-operated rats, but fully prevented hyporeactivity to KCl, phenylephrine and angiotensin II in vessels from CLP rats. This protective effect was not associated with changes in hematological parameters or blood nitrate and nitrite. The refractoriness to contractile agents was accompanied by enhanced activity of MMP-2 in aorta from CLP rats, which was abrogated by MMP inhibitors. CLP-induced sepsis did not impair the levels of MMP-2 in aorta, but significantly reduced calponin-1, a regulatory protein of vascular contraction. In addition, augmented levels of TIMP-1 were found in vessels from CLP rats. All these differences were prevented by either doxycycline or ONO-4817. Our study shows, for the first time in the CLP rat model of sepsis, that the vascular refractoriness to different contractile agents induced by polymicrobial sepsis is associated with increased activity of MMP-2 and reduced amounts of calponin-1 in the aorta. These findings reinforce the importance of the enhanced activity of MMPs for vascular failure in septic shock.

Reduction in renal blood flow following administration of norepinephrine and phenylephrine in septic rats treated with Kir6.1 ATP-sensitive and KCa1.1 calcium-activated K+ channel blockers.

We evaluated the effects of K+ channel blockers in the vascular reactivity of in vitro perfused kidneys, as well as on the influence of vasoactive agents in the renal blood flow of rats subjected to the cecal ligation and puncture (CLP) model of sepsis. Both norepinephrine and phenylephrine had the ability to increase the vascular perfusion pressure reduced in kidneys of rats subjected to CLP at 18 h and 36 h before the experiments. The non-selective K+ channel blocker tetraethylammonium, but not the Kir6.1 blocker glibenclamide, normalized the effects of phenylephrine in kidneys from the CLP 18 h group. Systemic administration of tetraethylammonium, glibenclamide, or the KCa1.1 blocker iberiotoxin, did not change the renal blood flow in control or septic rats. Norepinephrine or phenylephrine also had no influence on the renal blood flow of septic animals, but its injection in rats from the CLP 18 h group previously treated with either glibenclamide or iberiotoxin resulted in an exacerbated reduction in the renal blood flow. These results suggest an abnormal functionality of K+ channels in the renal vascular bed in sepsis, and that the blockage of different subtypes of K+ channels may be deleterious for blood perfusion in kidneys, mainly when associated with vasoactive drugs.

Essential oil of Cymbopogon citratus (lemongrass) and geraniol, but not citral, promote gastric healing activity in mice

Cymbopogon citratus, popularly known as lemongrass, is used for the treatment of gastric, nervous and hypertensive disorders, in addition to its use in the food and pharmaceutical industries. This study evaluated the gastroprotective and gastric healing effect of essential oil of C. citratus (EOCC), citral and geraniol at doses of 1-100 mg/kg (p.o) on acute ethanol-induced ulcer and chronic acetic acid-induced ulcer. Histological and histochemical evaluation was also performed, as well as the in vitro evaluation of the effects of these phytochemicals on H+/K+-ATPase activity. In the ethanol-induced gastric ulcer, the minimum effective oral dose of EOCC, citral and geraniol were 10, 100 and 3 mg/kg, reducing the ulcer area by 51.67%, 96.57% and 55.74%, respectively, compared to vehicle group (25.82 ± 3.59 mm2). Moreover, EOCC (10 mg/kg, p.o) and geraniol (3 mg/kg), but not citral (100 mg/kg), accelerated the gastric healing process by 34.52 and 80.57%, compared to acetic-acid ulcerated group treated with vehicle (36.04 ± 1.03 mm2). These healing effects were confirmed histologically by the contraction of the ulcer base and by the enhancement on mucin staining in slices of ulcer site from mice treated with EOCC or geraniol. Interestingly, EOCC and citral at 100 μg/ml inhibited the H+/ K+-ATPase activity by 28.26% and 44.36%, whereas geraniol did not change this parameter. Together, these findings confirm the gastroprotective and healing gastric ulcer effects of essential oil from aerial parts of C. citratus and added the information that geraniol, but not citral, promotes healing effects on installed ulcers.

Diuretic and natriuretic effect of luteolin in normotensive and hypertensive rats: Role of muscarinic acetylcholine receptors

BACKGROUND Luteolin is a very common phenolic compound found in a wide variety of natural products. Although several biological properties have already been described regarding the beneficial effect of luteolin in the cardiovascular and renal system, no scientific research explored its potential effect as a diuretic agent in experimental trials. METHODS Groups of male normotensive (NTR) and spontaneously hypertensive rats (SHR) were orally treated with vehicle, hydrochlorothiazide or luteolin. In another experimental set, in order to verify the possible mechanisms of luteolin-induced diuresis, NTR were treated with vehicle, hydrochlorothiazide, amiloride, L-NAME, indomethacin or atropine, 1h before receiving luteolin. The cumulative urine volume, electrolytes excretion, pH and osmolality were measured at the end of the experiment (after 8h). RESULTS Luteolin, at dose of 3mg/kg, was able to induce both diuretic and natriuretic effect in NTR and SHR groups, without interfering with urinary pH, K+ or Cl- levels. While Ca2+ content remained unchanged in urine from luteolin-treated group of NTR, luteolin reduced Ca2+ excretion in urine from SHR. The treatment with HCTZ and amiloride intensified luteolin-induced diuresis and natriuresis, with an interesting potassium-sparing effect, in addition to an increase in urinary osmolality levels. Moreover, the diuretic and natriuretic action of luteolin was fully avoided in the presence of atropine, a non-selective muscarinic receptor antagonist. CONCLUSIONS This study revealed the diuretic and natriuretic effect of luteolin in normotensive and hypertensive rats. Our data also showed the involvement of muscarinic acetylcholine receptors for the renal effects of luteolin.

Influence of Prostanoids in the Diuretic and Natriuretic Effects of Extracts and Kaempferitrin from Bauhinia forficata Link Leaves in Rats

Although Bauhinia forficata Link is popularly used in Brazil to induce diuresis, no scientific investigation has focused on demonstrating its efficacy in preclinical trials. For that, normotensive male Wistar and spontaneously hypertensive rats were used to test the effect of extracts and kaempferitrin obtained from Bauhinia forficata leaves in the experimental model of diuresis. Cumulative urine volume, Na+ and K+ excretion, calcium, creatinine, prostaglandin E2, pH, density, and conductivity were measured at the end of the experiment (after 8 or 24 h). The treatment with aqueous infusion, methanolic extract, trichloromethane, or ethyl acetate–butanolic fractions significantly increase urinary volume and electrolytes levels when orally given to rats, without altering the pH or density parameters. Kaempferitrin induced diuretic, natriuretic, but not kaliuretic effects in both normotensive and hypertensive rats. In addition, kaempferitrin enhanced urinary creatinine and prostaglandin E2 excretion, without modifying calcium levels. Kaempferitrin‐induced diuresis was unaffected by previous treatment with a nonselective inhibitor of nitric oxide synthase and neither with a nonselective muscarinic receptor antagonist. On the other hand, a cyclooxygenase inhibitor was able to decrease its effect when compared with vehicle‐treated rats, suggesting that the diuretic and natriuretic properties from kaempferitrin are associated with endogenous prostanoids generation. Copyright

Chemical composition and diuretic, natriuretic and kaliuretic effects of extracts of Mimosa bimucronata (DC.) Kuntze leaves and its majority constituent methyl gallate in rats

Some species of the genus Mimosa showed promising results in previous investigations, which include diuretic effect; however, no chemical analyses or animal model has been conducted so far to evaluate the biological properties of M. bimucronata.

Gastroprotective Value of Berries: Evidences from Methanolic Extracts of Morus nigra and Rubus niveus Fruits

This study evaluated the gastroprotective value of the methanol extracts from fruits of Morus nigra L. (black mulberry (MEMN)) and Rubus niveus Thunb (raspberry (MERN)). The total phenolic compounds and flavonoids were measured, as well as the in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenger activity. The gastroprotective effects of the extracts against 60% ethanol/0.3 M HCl were evaluated in mice. After that, the lipid hydroperoxides and reduced glutathione levels at ulcerated tissue were determined. The effects of extracts on H+/K+-ATPase activity were also verified. The extracts exhibited high contents of polyphenols; however, MERN presented 1.5-fold higher levels. The presence of flavonoids also was confirmed. In addition, MEMN (IC50 = 13.74 μg/mL) and MERN (IC50 = 14.97 μg/mL) scavenged DPPH radical. The MEMN reduced the ulcer area only at 300 mg/kg (p.o.) by 64.06%. Interestingly, MERN decreased the ulcer area in a superior potency (ED50 = 20.88 mg/kg), reducing the ulcer area by 81.86% at 300 mg/kg, and increased the gastric mucin levels. The antioxidant effects of extracts were evidenced by reduced lipoperoxides and increased reduction of glutathione amount in the gastric mucosa. However, MEMN or MERN did not change the H+/K+-ATPase activity. These results confirm that M. nigra and R. niveus are berries with a gastroprotective value by strengthening of gastric protective factors.

Propolis and Its Potential to Treat Gastrointestinal Disorders

There are a number of disorders that affect the gastrointestinal tract. Such disorders have become a global emerging disease with a high incidence and prevalence rates worldwide. Inflammatory and ulcerative processes of the stomach or intestines, such as gastritis, ulcers, colitis, and mucositis, afflict a significant proportion of people throughout the world. The role of herbal-derived medicines has been extensively explored in order to develop new effective and safe strategies to improve the available gastrointestinal therapies that are currently used in the clinical practice. Studies on the efficacy of propolis (a unique resinous aromatic substance produced by honeybees from different types of species of plants) are promising and propolis has been effective in the treatment of several pathological conditions. This review, therefore, summarizes and critiques the contents of some relevant published scientific papers (including those related to clinical trials) in order to demonstrate the therapeutic value of propolis and its active compounds in the treatment and prevention of gastrointestinal diseases.

Antioxidant and anti-inflammatory effect of plumieride in dextran sulfate sodium-induced colitis in mice

This study aimed to investigate the potential effect of plumieride, an iridoid glycoside isolated from Alamanda cathartica L. flowers, against dextran sulfate sodium (DSS)-induced colitis in mice. Colitis was induced in female swiss mice by adding DSS 3% to the drinking water. The animals were treated with vehicle (water), 5-aminosalicylic acid (100?mg/kg) or plumieride (10, 30 and 100?mg/kg) once a day, during 7 days. The body weight progression and the disease activity index was evaluated daily. On the eighth day, colons were collected for the measurement of the size, histological, histochemical, biochemical and inflammatory analysis. The cytotoxicity of plumieride on intestinal epithelial cell (IEC-6 cell line) was also evaluated. Plumieride, at dose of 100?mg/kg, significantly attenuated the mice weight loss, showed lower score in the disease activity index, diminished the colon shortening, improved the histological damage and avoided mucosa intestinal mucus depletion when compared with vehicle-treated only group. Moreover, plumieride was able to reduce the amount of colonic lipid hydroperoxides, while augmented reduced glutathione levels and superoxide dismutase activity. Although DSS intake stimulated an increase in myeloperoxidase activity and in tumor necrosis factor content on the colon tissue of the vehicle-treated group, the colons obtained from mice treated with plumieride did not present any of these changes. Taking together, the results of the present study disclose that plumieride exhibited a significant efficacy in attenuating the parameters of experimental ulcerative colitis, which may be mediated by an antioxidant and anti-inflammatory effect.