Dominga Lapi

Protective effects of Lactobacillus paracasei F19 in a rat model of oxidative and metabolic hepatic injury

The liver is susceptible to such oxidative and metabolic stresses as ischemia-reperfusion (I/R) and fatty acid accumulation. Probiotics are viable microorganisms that restore the gut microbiota and exert a beneficial effect on the liver by inhibiting bacterial enzymes, stimulating immunity, and protecting intestinal permeability. We evaluated Lactobacillus paracasei F19 (LP-F19), for its potential protective effect, in an experimental model of I/R (30 min ischemia and 60 min reperfusion) in rats fed a standard diet or a steatogen [methionine/choline-deficient (MCD)] diet. Both groups consisted of 7 sham-operated rats, 10 rats that underwent I/R, and 10 that underwent I/R plus 8 wk of probiotic dietary supplementation. In rats fed a standard diet, I/R induced a decrease in sinusoid perfusion (P < 0.001), severe liver inflammation, and necrosis besides an increase of tissue levels of malondialdehyde (P < 0.001), tumor necrosis factor-alpha (P < 0.001), interleukin (IL)-1beta (P < 0.001), and IL-6 (P < 0.001) and of serum levels of transaminase (P < 0.001) and lipopolysaccharides (P < 0.001) vs. sham-operated rats. I/R also induced a decrease in Bacterioides, Bifidobacterium, and Lactobacillus spps (P < 0.01, P < 0.001, and P < 0.001, respectively) and an increase in Enterococcus and Enterobacteriaceae (P < 0.01 and P < 0.001, respectively) on intestinal mucosa. The severity of liver and gut microbiota alterations induced by I/R was even greater in rats with liver inflammation and steatosis, i.e., MCD-fed animals. LP-F19 supplementation significantly reduced the harmful effects of I/R on the liver and on gut microbiota in both groups of rats, although the effect was slightly less in MCD-fed animals. In conclusion, LP-F19 supplementation, by restoring gut microbiota, attenuated I/R-related liver injury, particularly in the absence of steatosis.

Remodeling of Cerebral Microcirculation after Ischemia-Reperfusion.

Clinical and experimental studies have been focused on the pathophysiological mechanisms induced by brain ischemia-reperfusion injury. Recovery events, such as neurogenesis, angiogenesis and the growth of new blood vessels from the preexisting vascular tree, have been intensively studied in the last decades to clarify the vascular remodeling crucial for stroke outcome. This review aims to discuss the cerebral microcirculation remodeling induced by ischemia-reperfusion and the mechanisms involved in angiogenesis and vasculogenesis. The first in vivo observations were focused on anastomotic shunting of cerebral blood flow (CBF) in experimental and clinical models. Thereafter, vascular remodeling induced by cerebral ischemia-reperfusion was reported in mice and rats. Successively, other studies have assessed that within 30 days of middle cerebral artery (MCA) occlusion in rats, there is an increase in CBF and recovery from stroke. Recently, rats submitted to transient MCA occlusion showed pial microcirculation remodeling with the formation of new arterioles sprouting from penumbra vessels and overlapping the ischemic core. This review focuses on the production and/or activation of vasculotrophic factors able to trigger and facilitate microvascular remodeling. Vascular endothelial growth factor and endothelium-released nitric oxide appear to be the main factors involved in the formation of new vessels during microvascular remodeling. These studies are fundamental for consequent interventions on molecular targets, useful for fostering vascular remodeling and the recovery of functions.

Protective Effects of Quercetin on Rat Pial Microvascular Changes during Transient Bilateral Common Carotid Artery Occlusion and Reperfusion

The aim of this study was to assess the in vivo effects of quercetin on pial microvascular responses during transient bilateral common carotid artery occlusion (BCCAO) and reperfusion. Rat pial microcirculation was visualized by fluorescence microscopy through a closed cranial window. Pial arterioles were classified in five orders of branchings. Capillaries were assigned order 0, the smallest arterioles order 1, and the largest ones order 5. In ischemic rats, 30 min BCCAO and 60 min reperfusion caused arteriolar diameter decrease (by 14.5 ± 3.3% of baseline in order 2), microvascular leakage [0.47 ± 0.04, normalized gray levels (NGL)], leukocyte adhesion in venules (9 ± 2/100 μm venular length, v.l./30 s), and reduction of capillary perfusion (by 40 ± 7% of baseline). Moreover, at the end of BCCAO and reperfusion there was a significant increase in reactive oxygen species (ROS) formation when compared with baseline. Quercetin highest dose determined dilation in all arteriolar orders (by 40 ± 4% of baseline in order 2) and prevented microvascular permeability (0.15 ± 0.02 NGL), leukocyte adhesion (3 ± 1/100 μm v.l./30 s) as well as ROS formation, while capillary perfusion was protected. Inhibition of endothelial nitric oxide synthase (NOS) prior to quercetin reduced arteriolar dilation (order 2 diameter increase by 10.3 ± 2.5% of baseline) and caused permeability increase (0.29 ± 0.03 NGL); inhibition of neuronal NOS or inducible NOS did not affect quercetin-induced effects. Inhibition of guanylyl cyclase prior to quercetin reversed the quercetin’s effects on pial arteriolar diameter and leakage. In conclusion, quercetin was able to protect pial microcirculation from ischemia–reperfusion damage inducing arteriolar dilation likely by nitric oxide release. Moreover, quercetin scavenger activity blunted ROS formation preserving the blood–brain barrier integrity.

Rat Pial Microvascular Responses to Transient Bilateral Common Carotid Artery Occlusion and Reperfusion: Quercetin’s Mechanism of Action

The aim of the present study was to assess quercetin’s mechanism of action in rat pial microvessels during transient bilateral common carotid artery occlusion (BCCAO) and reperfusion. Rat pial microcirculation was visualized using fluorescence microscopy through a closed cranial window. Pial arterioles were classified in five orders of branchings. In ischemic rats, 30 min BCCAO and 60 min reperfusion caused arteriolar diameter decrease, microvascular leakage, leukocyte adhesion in venules, and reduction of capillary perfusion. Quercetin highest dose determined dilation in all arteriolar orders, by 40 ± 4% of baseline in order 2 vessels, and prevented microvascular permeability [0.15 ± 0.02 normalized gray levels (NGL)], leukocyte adhesion, and capillary failure. Protein kinase C (PKC) inhibition exerted by chelerythrine prior to quercetin attenuated quercetin-induced effects: order 2 arterioles dilated by 19.0 ± 2.4% baseline, while there was an increase in permeability (0.40 ± 0.05 NGL) and leukocyte adhesion with a marked decrease in capillary perfusion. Tyrosine kinase (TK) inhibition by tyrphostin 47 prior to quercetin lessened smaller pial arterioles responses, dilating by 20.7 ± 2.5% of baseline, while leakage increased (0.39 ± 0.04 NGL) sustained by slight leukocyte adhesion and ameliorated capillary perfusion. Inhibition of endothelium nitric oxide synthase (eNOS) by NG-nitro-L-arginine-methyl ester (L-NAME) prior to PKC or TK reduced the quercetin’s effects on pial arteriolar diameter and leakage. eNOS inhibition by L-NAME reduced quercetin effects on pial arteriolar diameter and leakage. Finally, combined inhibition of PKC and TK prior to quercetin abolished quercetin-induced effects, decreasing eNOS expression, while blocking ATP-sensitive potassium (KATP) channels by glibenclamide suppressed arteriolar dilation. In conclusion, the protective effects of quercetin could be due to different mechanisms resulting in NO release throughout PKC and TK intracellular signaling pathway activation.

Prolonged hypotensive and bradycardic effects of passive mandibular extension: evidence in normal volunteers.

Various procedures involving stimulations of facial regions are known to induce so-called trigemino-cardiac reflexes that entail a decrease of heart rate and blood pressure. We here report the effects of a specific stimulation that consists in a submaximal passive mandibular extension obtained by means of a dilatator applied for 10 minutes between the upper and lower incisor teeth, associated with partial active masticatory movements. Blood pressure and heart rate were determined in 18 young normal volunteers by Omron M4, before (20 minutes), during (10 minutes) and after mandibular extension (80 minutes) and under control conditions (same overall duration without stimulation). While control values remained stable, mandibular extension was followed by a progressive decline of both blood pressure (up to about 12/11 mmHg) and heart rate (up to about 13 bpm), statistically confirmed by ANOVA both on absolute values and on changes from basal values. The decline of systolic blood pressure and heart rate significantly correlated with basal values. The present findings indicate that submaximal opening of the mouth, associated to partial masticatory movements, induces a prolonged reduction of blood pressure and heart rate in normotensive volunteers.

Persistent effects after trigeminal nerve proprioceptive stimulation by mandibular extension on rat blood pressure, heart rate and pial microcirculation.

The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation.

Effects of Oleuropein and Pinoresinol on Microvascular Damage Induced by Hypoperfusion and Reperfusion in Rat Pial Circulation

The present study was aimed to assess the in vivo acute effects of oleuropein or/and pinoresinol, polyphenols widely diffused in natural sources, on rat pial microvascular responses during transient BCCAO and reperfusion.

Rat pial microvascular responses to melatonin during bilateral common carotid artery occlusion and reperfusion

Abstract: The present study assessed the in vivo rat pial microvascular responses induced by melatonin during brain hypoperfusion and reperfusion (RE) injury. Pial microcirculation of male Wistar rats was visualized by fluorescence microscopy through a closed cranial window. Hypoperfusion was induced by bilateral common carotid artery occlusion (BCCAO, 30 min); thereafter, pial microcirculation was observed for 60 min. Arteriolar diameter, permeability increase, leukocyte adhesion to venular walls, perfused capillary length (PCL), and capillary red blood cell velocity (VRBC) were investigated by computerized methods. Melatonin (0.5, 1, 2 mg/kg b.w.) was intravenously administered 10 min before BCCAO and at the beginning of RE. Pial arterioles were classified in five orders according to diameter, length, and branchings. In control group, BCCAO caused decrease in order 2 arteriole diameter (by 17.5 ± 3.0% of baseline) that was reduced by 11.8 ± 1.2% of baseline at the end of RE, accompanied by marked leakage and leukocyte adhesion. PCL and capillary VRBC decreased. At the end of BCCAO, melatonin highest dosage caused order 2 arteriole diameter reduction by 4.6 ± 2.0% of baseline. At RE, melatonin at the lower dosages caused different arteriolar responses. The highest dosage caused dilation in order 2 arteriole by 8.0 ± 1.5% of baseline, preventing leakage and leukocyte adhesion, while PCL and VRBC increased. Luzindole (4 mg/kg b.w.) prior to melatonin caused order 2 arteriole constriction by 12.0 ± 1.5% of baseline at RE, while leakage, leukocyte adhesion, PCL and VRBC were not affected. Prazosin (1 mg/kg b.w.) prior to melatonin did not significantly change melatonin’s effects. In conclusion, melatonin caused different responses during hypoperfusion and RE, modulating pial arteriolar tone likely by MT1 and MT2 melatonin receptors while preventing blood–brain barrier changes through its free radical scavenging action.

Trigeminocardiac Reflex by Mandibular Extension on Rat Pial Microcirculation: Role of Nitric Oxide

In the present study we have extended our previous findings about the effects of 10 minutes of passive mandibular extension in anesthetized Wistar rats. By prolonging the observation time to 3 hours, we showed that 10 minutes mandibular extension caused a significant reduction of the mean arterial blood pressure and heart rate respect to baseline values, which persisted up to 160 minutes after mandibular extension. These effects were accompanied by a characteristic biphasic response of pial arterioles: during mandibular extension, pial arterioles constricted and after mandibular extension dilated for the whole observation period. Interestingly, the administration of the opioid receptor antagonist naloxone abolished the vasoconstriction observed during mandibular extension, while the administration of Nω-Nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, abolished the vasodilation observed after mandibular extension. Either drug did not affect the reduction of mean arterial blood pressure and heart rate induced by mandibular extension. By qRT-PCR, we also showed that neuronal nitric oxide synthase gene expression was significantly increased compared with baseline conditions during and after mandibular extension and endothelial nitric oxide synthase gene expression markedly increased at 2 hours after mandibular extension. Finally, western blotting detected a significant increase in neuronal and endothelial nitric oxide synthase protein expression. In conclusion mandibular extension caused complex effects on pial microcirculation involving opioid receptor activation and nitric oxide release by both neurons and endothelial vascular cells at different times.

Dietary protein intake in sarcopenic obese older women

Objective To determine the prevalence of sarcopenia in a population of obese older women and to assess the effect of a diet moderately rich in proteins on lean mass in sarcopenic obese older women. Materials and methods A total of 1,030 females, >65 years old, body mass index >30 kg/m2, were investigated about their nutritional status. Muscle mass (MM) was estimated according to the Janssen equation (MM =0.401× height2/resistance measured at 50 kHz +3.825× sex −0.071× age +5.102). Sarcopenia was defined according to the MM index, MM/height2 (kg/m2), as two standard deviations lower than the obesity-derived cutoff score (7.3 kg/m2). A food-frequency questionnaire was used to measure participants’ usual food intake during the previous 3 months. Moreover, a group of sarcopenic obese older women (n=104) was divided in two subgroups: the first (normal protein intake [NPI], n=50) administered with a hypocaloric diet (0.8 g/kg desirable body weight/day of proteins), and the second treated with a hypocaloric diet containing 1.2 g/kg desirable body weight/day of proteins (high protein intake [HPI], n=54), for 3 months. Dietary ingestion was estimated according to a daily food diary, self-administered, and three reports of nonconsecutive 24-hour recall every month during the follow-up. Results The 104 women were classified as sarcopenic. After dieting, significant reductions in body mass index were detected (NPI 30.7±1.3 vs 32.0±2.3 kg/m2, HPI 30.26±0.90 vs 31.05±2.90 kg/m2; P<0.01 vs baseline). The MM index presented significant variations in the NPI as well as in the HPI sarcopenic group (NPI 6.98±0.1 vs 7.10±0.2 kg/m2, HPI 7.13±0.4 vs 6.96±0.1 kg/m2; P<0.01 vs baseline). Conclusion A diet moderately rich in proteins was able to preserve MM in sarcopenic women. Therefore, adequate protein intake could contribute to the prevention of lean-mass loss associated with weight reduction in obese older people.