Gisele Agustini Lovatel

Treadmill exercise induces age-related changes in aversive memory, neuroinflammatory and epigenetic processes in the rat hippocampus.

It has been described that exercise can modulate both inflammatory response and epigenetic modifications, although the effect of exercise on these parameters during the normal brain aging process yet remains poorly understood. Here, we investigated the effect of aging and treadmill exercise on inflammatory and epigenetic parameters specifically pro and anti-inflammatory cytokines levels, activation of NF-kB and histone H4 acetylation levels in hippocampus from Wistar rats. Additionally, we evaluated aversive memory through inhibitory avoidance task. Rats of 3 and 20 months of age were assigned to non-exercised (sedentary) and exercised (running daily for 20 min for 2 weeks) groups. The effect of daily forced exercise in the treadmill was assessed. The levels of inflammatory and epigenetic parameters were determined 1h, 18 h, 3 days or 7 days after the last training session of exercise. It was observed an age-related decline on aversive memory, as well as aged rats showed increased hippocampal levels of inflammatory markers, such as TNFα, IL1-β and NF-kB and decreased IL-4 levels, an anti-inflammatory cytokine. Moreover, lower levels of global histone H4 acetylation were also observed in hippocampi from aged rats. Interestingly, there was a significant correlation between the biochemical markers and the inhibitory avoidance test performance. The forced exercise protocol ameliorated aging-related memory decline, decreased pro-inflammatory markers and increased histone H4 acetylation levels in hippocampi 20-months-old rats, while increased acutely IL-4 levels in hippocampi from young adult rats. Together, these results suggest that an imbalance of inflammatory markers might be involved to the aging-related aversive memory impairment. Additionally, our exercise protocol may reverse aging-related memory decline through improving cytokine profile.

Effect of different exercise protocols on histone acetyltransferases and histone deacetylases activities in rat hippocampus

Regular and moderate exercise has been considered an interesting neuroprotective strategy. Although the mechanisms by which physical exercise alters brain function are not clear, it appears that neuroprotective properties of exercise could be related to chromatin remodeling, specifically the induction of histone acetylation through modulation of histone deacetylases (HDAC) and histone acetyltransferases (HAT) activities. The aim of the present work was to investigate the effect of exercise on HDAC and HAT activities in rat whole hippocampus at different times after treadmill. Adult male Wistar rats were assigned to non-exercised (sedentary) and exercised groups on different protocols: a single session of treadmill exercise (running for 20 min) and a chronic treadmill protocol (running once daily for 20 min, for 2 weeks). The effects of exercise on HDAC and HAT activities were measured immediately, 1 h and 18 h after the single session or the last training session of chronic treadmill exercise using specific assay kits. The single session of treadmill exercise reduced HDAC activity, increased HAT activity and increased the HAT/HDAC balance in rat hippocampus immediately and 1 h after exercise, an indicative of histone hyperacetylation status. The acetylation balance was also influenced by the circadian rhythm, since the HAT/HDAC ratio was significantly decreased in the early morning in all groups when compared to the afternoon. These data support the hypothesis that exercise neuroprotective effects may be related, at least in part, to acetylation levels through modulation of HAT and HDAC activities. We also demonstrated circadian changes in the HAT and HDAC activities and, consequently, in the acetylation levels.

Exercise induces age-dependent changes on epigenetic parameters in rat hippocampus: a preliminary study.

Regular exercise improves learning and memory, including during aging process. Interestingly, the imbalance of epigenetic mechanisms has been linked to age-related cognitive deficits. However, studies about epigenetic alterations after exercise during the aging process are rare. In this preliminary study we investigated the effect of aging and exercise on DNA methyltransferases (DNMT1 and DNMT3b) and H3-K9 methylation levels in hippocampus from 3 and 20-months aged Wistar rats. The animals were submitted to two exercise protocols: single session or chronic treadmill protocol. DNMT1 and H3-K9 methylation levels were decreased in hippocampus from aged rats. The single exercise session decreased both DNMT3b and DNMT1 levels in young adult rats, without any effect in the aged group. Both exercise protocols reduced H3-K9 methylation levels in young adult rats, while the single session reversed the changes on H3-K9 methylation levels induced by aging. Together, these results suggest that an imbalance on DNMTs and H3-K9 methylation levels might be linked to the brain aging process and that the outcome to exercise seems to vary through lifespan.

Environmental enrichment prevents behavioral deficits and oxidative stress caused by chronic cerebral hypoperfusion in the rat

AIMS The aim of the present study was to evaluate the neuroprotective effects of environmental enrichment (EE), assessed by cognitive activity in the Morris water maze, and on brain oxidative status, through measurement of macromolecules damage, lipid peroxidation levels, total cellular thiols and antioxidant enzymes in hippocampus, striatum and cerebral cortex. MAIN METHODS Adult male Wistar rats were submitted to the modified permanent bilateral occlusion of the common carotid arteries (2VO) method, with right common carotid artery being first occluded, and tested three months after the ischemic event. Cognitive and physical stimulation, named Environmental Enrichment, consisted of one-hour sessions run 3 times per week during 12weeks, following two different stimulation protocols: pre-ischemia and pre+post-ischemia. Rats were then tested for both reference and working spatial memory tasks in the water maze and later sacrificed for measurement of oxidative stress parameters. KEY FINDINGS A significant cognitive deficit was found in both spatial tasks after hypoperfusion; this effect was reversed in the 2VO enriched group. Moreover, hippocampal oxidative damage and antioxidant enzyme activity were decreased by environmental enrichment. SIGNIFICANCE These results suggest that both stimulation protocols exert a neuroprotective effect against the cognitive impairment and the reduction of biomarkers for oxidative damage caused by chronic cerebral hypoperfusion.

Inflammatory response and oxidative stress in developing rat brain and its consequences on motor behavior following maternal administration of LPS and perinatal anoxia.

Cerebral palsy (CP) is a disorder of locomotion, posture and movement that can be caused by prenatal, perinatal or postnatal insults during brain development. An increased incidence of CP has been correlated to perinatal asphyxia and maternal infections during gestation. The effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) associated or not with perinatal anoxia (PA) in oxidative and inflammatory parameters were examined in cerebral cortices of newborns pups. Concentrations of TNF‐α, IL‐1, IL‐4, SOD, CAT and DCF were measured by the ELISA method. Other newborn rats were assessed for neonatal developmental milestones from day 1 to 21. Motor behavior was also tested at P29 using open‐field and Rotarod. PA alone only increased IL‐1 expression in cerebral cortex with no changes in oxidative measures. PA also induced a slight impact on development and motor performance. LPS alone was not able to delay motor development but resulted in changes in motor activity and coordination with increased levels of IL‐1 and TNF‐α expression associated with a high production of free radicals and elevated SOD activity. When LPS and PA were combined, changes on inflammatory and oxidative stress parameters were greater. In addition, greater motor development and coordination impairments were observed. Prenatal exposure of pups to LPS appeared to sensitize the developing brain to effects of a subsequent anoxia insult resulting in an increased expression of pro‐inflammatory cytokines and increased free radical levels in the cerebral cortex. These outcomes suggest that oxidative and inflammatory parameters in the cerebral cortex are implicated in motor deficits following maternal infection and perinatal anoxia by acting in a synergistic manner during a critical period of development of the nervous system.

Treadmill training improves motor skills and increases tyrosine hydroxylase immunoreactivity in the substantia nigra pars compacta in diabetic rats.

The aim of this study was to evaluate the effects of treadmill training on motor skills and immunoreactivity to tyrosine hydroxylase in the substantia nigra pars compacta and ventral tegmental area from diabetic rats induced by streptozotocin. Male Wistar rats were divided into three groups: control, diabetic and trained diabetic. Treadmill training was performed for 8weeks. Blood glucose concentrations and body weight were evaluated 48h after diabetes induction and every 30days thereafter. Motor skills were evaluated on the rotarod and open field tests. Then, animals were transcardially perfused and the brains were post-fixed, cryoprotected and sectioned in a cryostat. Immunohistochemistry for tyrosine hydroxylase analyses was done in the ventral tegmental area and in the substantia nigra. Motor skills showed that diabetic animals had a decrease in the latency to fall and enhanced number of falls in the rotarod test compared to control and trained diabetic animals. In the open field, diabetic animals had a decrease in the number of crossed squares, rearings and spent a less time moving compared to control and trained diabetic animals. In diabetic animals, optical densitometry of immunohistochemistry showed that tyrosine hydroxylase reaction decreased in the ventral tegmental area and in the neurons and process in the substantia nigra. In the later region, that decrease was reversed by treadmill training. In conclusion, we demonstrated that treadmill training can reverse the loss of the motor skills, which was correlated to tyrosine hydroxylase immunoreactivity in the substantia nigra of diabetic animals without pharmacological treatment.

Thermographic evaluation of hind paw skin temperature and functional recovery of locomotion after sciatic nerve crush in rats

INTRODUCTION: Peripheral nerves are often damaged by direct mechanical injury, diseases, and tumors. The peripheral nerve injuries that result from these conditions can lead to a partial or complete loss of motor, sensory, and autonomic functions, which in turn are related to changes in skin temperature, in the involved segments of the body. The aim of this study was to evaluate the changes in hind paw skin temperature after sciatic nerve crush in rats in an attempt to determine whether changes in skin temperature correlate with the functional recovery of locomotion. METHODS: Wistar rats were divided into three groups: control (n = 7), sham (n = 25), and crush (n = 25). All groups were subjected to thermographic, functional, and histological assessments. RESULTS: ΔT in the crush group was different from the control and sham groups at the 1st, 3rd and 7rd postoperative days (p<0.05). The functional recovery from the crush group returned to normal values between the 3rd and 4th week post-injury, and morphological analysis of the nerve revealed incomplete regeneration at the 4th week after injury. DISCUSSION: This study is the first demonstration that sciatic nerve crush in rats induces an increase in hind paw skin temperature and that skin temperature changes do not correlate closely with functional recovery

Time-dependent effects of treadmill exercise on aversive memory and cyclooxygenase pathway function

Exercise induces brain function adaptations and improves learning and memory; however the time window of exercise effects has been poorly investigated. Studies demonstrate an important role for cyclooxygenase-2 (COX-2) pathway function in the mechanisms underlying memory formation. The aim of present work was to investigate the effects of treadmill exercise on aversive memory and COX-2, PGE(2) and E-prostanoid receptors contents in the rat hippocampus at different time points after exercise has ended. Adult male Wistar rats were assigned to non-exercised (sedentary) and exercised (running daily for 20min, for 2weeks) groups. The inhibitory avoidance task was used to assess aversive memory and the COX-2, PGE(2) and E-prostanoid receptors (EP1, EP2, EP3 and EP4) levels were determined 1h, 18h, 3days or 7days after the last training session of treadmill exercise. The step down latency in the inhibitory avoidance, COX-2 and EP4 receptors levels were acutely increased by exercise, with a significant positive correlation between aversive memory performance and COX-2 levels. Increased EP2 content decreased PGE(2) levels were observed 7days after the last running session. The treadmill exercise protocol facilitates inhibitory avoidance memory and induces time-dependent changes on COX-2 pathways function (COX-2, PGE(2) and EP receptors).

Diabetes increases mechanical sensitivity and causes morphological abnormalities in the sural nerve that are prevented by treadmill training

In this investigation we evaluated the effects of treadmill training on mechanical sensitivity and sural nerve morphology in diabetic rats.

The effects of treadmill training on young and mature rats after traumatic peripheral nerve lesion

The purpose of this study was to investigate the possible effects of a treadmill training program on regeneration in young (3-month-old) and mature (13-month-old) rats with sciatic nerve crush using functional, electrophysiological, and morphometric analyses. When compared to both the young and mature untrained injury groups, those groups that underwent a treadmill training showed improved sensorimotor function evaluated by narrow beam test (p<0.04 and p<0.001, respectively), while muscle action potential amplitude was only greater in the young group (p<0.02). The treadmill training program was able to reduce myelinated fiber density in the young group (p<0.001), which appeared to increase after nerve injury (poly-innervation), but decreased with training, which means that the innervation became more functional. The data indicate that treadmill training is able to promote functional, electrophysiological and morphological recovery in young animals. However, in mature animals, improvement was only seen in terms of functional recovery.