Sévan Kaloustian

Behavioural signs of depression and apoptosis in the limbic system following myocardial infarction: effects of sertraline

Abstract Depression is diagnosed in 15–30% of patients following myocardial infarction (MI) and this may also be observed in the rat. We measured the effects of the antidepressant sertraline on behavioural and biochemical events following MI in a rat model. Following surgery, MI rats and sham controls were treated with sertraline (10 mg/kg, i.p.) or saline. Subgroups of rats were tested for behavioural depression 14 days after surgery. Apoptosis was estimated in other rats by measuring caspase-3 activity and TUNEL positive cells (3 days after surgery) in limbic structures (amygdale, hippocampus, hypothalamus, frontal and prefrontal cortices). Bax/Bcl-2 ratio was measured 14 days after surgery. Behavioural signs of depression (decreased sucrose intake and forced swimming time) were found in saline-treated MI rats but not in sertraline-treated rats. Compared with controls, caspase-3 activity and TUNEL positive cells were significantly increased in most limbic structures of MI rats. High prefrontal Bax/Bcl-2 ratio in MI rats correlated with low forced swimming time. Apoptosis was not found in sertraline-treated MI rats. These results establish the bases of a rat model of depression following MI and show for the first time that a selective serotonin reuptake inhibitor prevents both behavioural and biochemical markers in this model.

Apoptosis detected in the amygdala following myocardial infarction in the rat.

BACKGROUND Myocardial infarction (MI) contains a risk factor for developing episodes of Major Depressive Disorder (MDD). Apoptosis is commonly observed in the reperfused myocardial infarcted heart, and recent findings suggest the existence of apoptosis in MDD. Cytokines, which are released by ischemic myocardium and which may induce apoptosis, have been proposed as a possible cause for MDD. METHODS Myocardial infarction was produced in anesthetized rats by a 40-minute occlusion of the left anterior descending coronary artery followed by 72 hours of reperfusion. Determination of apoptosis was done in the amygdala, hippocampus and vermis of MI and Sham rats treated or not with pentoxyfilline (PTX), a cytokine synthesis inhibitor (10 mg/kg/day intraperitoneal). RESULTS Compared to Sham rats, the amygdala of MI rats showed significantly reduced P13K activity, increased Bax/Bcl-2 ratio, caspase-3 activity, and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling)-positive cells. The effect of MI on apoptosis was completely reversed in presence of PTX. No statistical difference was observed in the hippocampus and the vermis in the different groups for any of the biochemical measurements. CONCLUSIONS These results indicated that MI induce apoptosis in amygdala by a cytokine-sensitive mechanism and may explain the MDD observed following myocardial infarction.

Training improves the electrophysiological properties of lumbar neurons and locomotion after thoracic spinal cord injury in rats.

The aim of the present study was to evaluate the effect of a stepping-based rehabilitation program in voluntary wheel cages on the functional recovery and electrophysiological properties of neurons in the rat lumbar spinal cord after compressive thoracic (T10) spinal cord injury (SCI). A significant decrease in stance/swing duration and the number of limbs simultaneously in the stance phase was seen in trained compared to sedentary rats at 28 days after SCI (p<0.05). These kinematic improvements were associated with a significant increase in the amplitude of extracellular recordings from the tibial motoneuron pool in response to descending neuronal drive as well as significant amelioration of electrophysiological properties assessed from intracellular recordings. In fact, electrophysiological properties were not significantly different between uninjured controls and SCI-trained rats. Brain-derived neurotrophic factor (BDNF) levels were significantly elevated in the lumbar spinal cord of SCI-trained rats compared to SCI-sedentary controls. The data support a therapeutic role of increased neuromuscular activity in promoting functional recovery and suggest that it might occur via the beneficial effects of neurotrophic factors on neuronal plasticity.

Lactobacillus helveticus and Bifidobacterium longum taken in combination reduce the apoptosis propensity in the limbic system after myocardial infarction in a rat model

Myocardial infarction (MI) stimulates the release of pro-inflammatory substances that induce apoptosis in the limbic system. Pro-inflammatory cytokines are considered as the root cause of apoptosis, although the mechanism is not fully explained and/or understood at this time. In addition, depression may induce gastrointestinal perturbations that maintain the elevated levels of pro-inflammatory cytokines. It has been shown that some specific probiotic formulations may reduce gastrointestinal problems induced by stress and the pro/anti-inflammatory cytokine ratio. Therefore, we hypothesised that probiotics, when given prophylactically, may diminish the apoptosis propensity in the limbic system following a MI. Male adult Sprague-Dawley rats were given probiotics (Lactobacillus helveticus and Bifidobacterium longum in combination) or placebo in their drinking-water for four consecutive weeks. A MI was then induced in the rats by occluding the left anterior coronary artery for 40 min. Rats were killed following a 72 h reperfusion period. Infarct size was not different in the two groups. Bax/Bcl-2 (pro-apoptotic/anti-apoptotic) ratio and caspase-3 (pro-apoptotic) activity were reduced in the amygdala (lateral and medial), as well as in the dentate gyrus in the probiotics group when compared with the placebo. Akt activity (anti-apoptotic) was increased in these same three regions. No significant difference was observed in Ca1 and Ca3 for the different markers measured. In conclusion, the probiotics L. helveticus and B. longum, given in combination as preventive therapy, reduced the predisposition of apoptosis found in different cerebral regions following a MI.

Escitalopram reduces circulating pro-inflammatory cytokines and improves depressive behavior without affecting sleep in a rat model of post-cardiac infarct depression

Myocardial infarction (MI) in rats is followed by a behavioral syndrome similar to human post-MI depression. We tested the effects of escitalopram, a selective serotonin reuptake inhibitor, on this syndrome. MI was induced in 19 Sprague-Dawley rats by occluding the left anterior descending coronary artery for 40min, followed by reperfusion. A sham-operated group of 20 rats was submitted to the same protocol without coronary artery occlusion. Fifteen minutes after the onset of reperfusion, escitalopram (10mg/kg/day, i.p.) or saline was infused continuously through osmotic minipumps. After 2weeks of treatment, the rats were tested for behavioral despair and anhedonia by the forced swimming and sucrose preference tests, respectively. They were then sacrificed, and blood levels of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), PGE(2) and corticosterone were measured. In a separate cohort of 24 rats, sleep was recorded after 2weeks of post-MI treatment with escitalopram or saline. In MI rats, behavioral despair and anhedonia were blocked by escitalopram but prolonged sleep latency, low total sleep time and short latency to paradoxical sleep (PS) were not; escitalopram decreased PS in sham controls. Plasma TNF-α, PGE(2), and corticosterone levels were higher in MI rats than in the controls. Escitalopram lowered TNF-α, IL-1β, and PGE(2) levels in both groups of rats while IL-6 showed no differences whatsoever. Escitalopram reverses post-MI behavioral syndrome in rats through a mechanism that could involve a reduction of pro-inflammatory cytokines and PGE(2). It has limited effects on sleep disorders in MI rats but reduces PS in control rats.

Apoptosis time course in the limbic system after myocardial infarction in the rat.

Apoptosis is known to occur in the limbic system after myocardial infarction (MI) in the rat. Our study was designed to evaluate the time course dynamics of this phenomenon in limbic areas. Apoptosis, i.e., caspase-3 activity and the number of terminal dUTP nick-end labelling-positive cells, as well as brain-derived neurotrophic factor (BDNF) were quantitated in sham-operated controls and MI rats 1, 2 and 7 days after surgery. Both apoptosis parameters were increased throughout, although in different structures: the CA1 region of the hippocampus and the medial amygdala at day 1, the CA1 region of the hippocampus and the lateral amygdala at day 2, and the frontal cortex at day 7. At day 2, BDNF was decreased in the prefrontal cortex and medial amygdala, whereas it was elevated in the dentate gyrus of the hippocampus; at day 7, BDNF was reduced in the frontal cortex and posterior hypothalamus but was augmented in the medial amygdala. These data indicate that post-MI apoptosis in the limbic system is a dynamic process occurring mainly in the hippocampus and amygdala during the first days after MI. The fact that BDNF was increased as early as 2 days after MI suggests that neurogenesis can occur rapidly in selected limbic regions after MI.

Pretreatment with pentoxifylline has antidepressant-like effects in a rat model of acute myocardial infarction.

We have observed that, after myocardial infarction (MI), rats display apoptosis in the limbic system that can be prevented by pentoxifylline (PTX), a proinflammatory cytokine inhibitor. We have hypothesized that reduction of apoptosis in the limbic system can attenuate the depressive behaviour occurring post-MI. The present study was, therefore, designed to assess the outcome of PTX on depressive behaviour manifesting after MI. Myocardial ischaemia, induced for 40 min in male Sprague–Dawley rats, was followed by reperfusion (MI groups). Sham groups were subjected to the same protocol without occlusion. PTX (10 mg/kg/day) or saline was administered intraperitoneally 15 min before ischaemia, and then every day until sacrifice. Two weeks after ischaemia, depression was evaluated by the forced swim test and the sucrose preference test. At the end of the experiment, the animals were sacrificed, and myocardial infarct size was examined along with plasma IL-1&bgr; concentrations. MI rats drank less sucrose in the sucrose preference test and were more immobile in the forced swim test than the sham controls. PTX reversed these behaviours in the MI group to a level similar to that in the untreated sham group, without affecting infarct size. PTX reduced plasma IL-1&bgr; concentrations in both sham and MI rats. We conclude that PTX administration significantly reverses the depressive-like behaviour seen after MI in rats.

Sustained cardioprotection afforded by A2A adenosine receptor stimulation after 72 hours of myocardial reperfusion.

This study was designed to determine whether cardioprotection afforded by A2A adenosine receptor stimulation can be sustained and to determine the effect of an A2A adenosine receptor agonist on Akt and cAMP response element binding protein (CREB) activation, as well as Hsp27 and Hsp70 protein expression in such events. The left anterior descending coronary artery was occluded for 40 minutes in anesthetized rats followed by 72 hours of reperfusion. A2A agonist (CGS21680 at 0.2 μg/kg/min) was administered for 120 minutes, starting either 5 minutes before (early) or after (late) the beginning of reperfusion. Infarct size was reduced significantly in the early compared with the control group (35.2 ± 1.9% and 52.5 ± 3.4%, respectively; P < 0.05), whereas no difference was observed with the late group (44.5 ± 7.1%). After 72 hours of reperfusion, drug administration was accompanied by Akt activation (early, 121.8 ± 17.6%; late, 118.1 ± 16.4%; P < 0.05), as well as elevated Hsp27 expression (early, 197.2 ± 27.7%; late, 203.8 ± 36.8%; P < 0.05); CREB activation and Hsp70 expression were not altered. In another set of experiments in which reperfusion was limited to 15 minutes, Akt was activated only in the early group (121.8 ± 17.6%; P < 0.05). Moreover, CREB was activated in both the early and late groups (98.4 ± 8.3% and 107.0 ± 6.5%, respectively; P < 0.05), whereas Hsp27 and Hsp70 expression were not altered. These results demonstrate that A2A adenosine receptor activation induces a sustained cardioprotection only if the therapy is instituted before reperfusion. This myocardial protection is associated by an early prosurvival Akt activation. CREB activation and Hsp27 content do not seem to be associated with cardioprotection because they are enhanced in both treated groups, suggesting indirect A2A agonist and pathology-related effects.

Chronic pretreatment with celecoxib reduces infarct size.

This study was designed to evaluate the effect of long-term pretreatment with celecoxib, a cyclooxygenase-2 inhibitor, on myocardial infarct size. Celecoxib (3 mg/kg/day i.p; n = 16) or vehicle (DMSO 50%; EtOH 15%; distilled water, n = 16) was administered chronically to male Sprague-Dawley rats through ALZET osmotic pumps for 28 days. Under anaesthesia, the animals were then subjected to left anterior descending coronary artery occlusion for 40 minutes, followed by 24-hour reperfusion. The results show that myocardial infarct size in celecoxib-treated rats was significantly reduced compared to the control group (37.5 ± 2.5% versus 48.0 ± 2.6% of the area at risk, P < 0.05, n = 10 per group). Accumulation of neutrophils, estimated by myeloperoxidase levels, indicated an increase in the ischemic area without any significant difference between groups. No significant difference was observed between the treated and vehicle groups in terms of plasma prostaglandin E2 and tumour necrosis factor-alpha. Apoptosis, evaluated by Bax/Bcl-2 and terminal dUTP nick-end labelled-positive cells, was significantly decreased in the subendocardial layer of the ischemic area in celecoxib-treated rats. This study indicates that pretreatment with celecoxib can reduce infarct size by a mechanism, which may involve apoptosis inhibition.

T-O-121 ESCITALOPRAM REDUCES INFLAMMATION AND IMPROVES BEHAVIOR WITHOUT AFFECTING SLEEP IN A RAT MODEL OF POST CARDIAC INFARCT DEPRESSION

awakenings in every spectral frequency studied, in relation to the group and presence or absence of recall. The various spectral bands evolved according to an underlying rhythm, which is attenuated in the presence of dream recall; this was more evident in Normal subjects. Verbal activities were negatively correlated with high frequency bands in C3, T5 and P3 electrodes in controls. Conclusion: Differences between recall and no recall were detected. The spectral frequency bands powers were attenuated with dream recall. A cyclic variation in spectral power was detected in association with recall. Verbal activities correlated with high frequencies in left centro-temporoparietal areas.