Estudiante

Purpose: Statins are selective inhibitors of 3-hydroxyl-3methyl-glutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme of the mevalonate pathway for cholesterol biosynthesis. Increasing evidence indicates that statins, particularly atorvastatin, are neuroprotective in several conditions, including stroke, cerebral ischemia, traumatic brain injury, and excitotoxic amino acid exposure. However, only a few studies have investigated whether statins modulate seizure activity. In the current study we investigated whether atorvastatin or simvastatin alters the seizures induced by pentylenetetrazol (PTZ), a classical convulsant. Methods: Adult male Wistar rats were treated with atorvastatin or simvastatin for 7 days (10 mg/kg/day). Seizure activity was induced by PTZ (60 mg/kg, i.p.), and evaluated by behavioral and electrographic methods. Cholesterol levels were determined by a standard spectrophotometric method. Blood-brain barrier (BBB) permeability was assessed by the fluorescein method. Atorvastatin levels in the plasma and cerebral cortex were determined by high-performance liquid chromatography tandem mass spectrometry. Key Findings: We found that oral atorvastatin treatment increased the latency to PTZ-induced general-ized seizures. In contrast, when the 7-day atorvastatin treatment was withheld for 1 day (i.e., atorvastatin withdrawal), PTZ-induced seizures were facilitated, as evidenced by a decrease in the latency to clonic and generalized tonic-clonic seizures induced by PTZ. In contrast, simvastatin treatment for 7 days (10 mg/kg/ day, p.o.), with or without withdrawal, did not alter PTZ-induced seizures. Interestingly, the effects of atorvastatin treatment and withdrawal were not accompanied by changes in plasma or cerebral cortex cholesterol levels or in the BBB permeability. Atorvastatin levels in the plasma and cerebral cortex after 7 days of treatment were above the half maximal inhibitory concentration for inhibition of HMG-CoA reductase, whereas atorvastatin was not detectable in the plasma or cerebral cortex following a 24 h washout period (atorvastatin withdrawal). Significance: We conclude that atorvastatin treatment and withdrawal have differential effects on pentylenetetrazol-induced seizures, which are not related to changes in plasma or cerebral cortex cholesterol levels or in BBB permeability. Additional studies are necessary to evaluate the molecular mechanisms underlying our findings as well as its clinical implications.

Rationale Spermidine (SPD) is an endogenous polyamine that modulates N-methyl-d-aspartate receptor functions, which has been reported to facilitate memory formation. Objectives In the current study, we investigated the involvement of nitric oxide in the facilitatory effect of SPD on the memory of adult male Wistar rats in the inhibitory avoidance task. Results The coadministration of the nonspecific NOS inhibitor N G nitro-l-arginine methyl ester (l-NAME) (0.1 nmol, intrahippocampus) with spermidine (0.2 nmol), immediately after training, prevented the memory improvement caused by spermidine in the avoidance inhibitory task. Spermidine increased nitrite and nitrate levels (NOX) in the hippocampus 30 min after its administration, and l-NAME coinjection prevented the stimulatory effect of spermidine on NOX levels. The systemic injection of 7-nitroindazole (30 mg/kg, i.p.), 30 min before training, impaired memory and did not prevent spermidine-induced increase of NOX levels in the hippocampus. Conclusions These results suggest that memory enhancement by spermidine is prevented by the nonspecific nitric oxide synthase inhibitor l-NAME.

Polyamines (putrescine, spermidine and spermine) are aliphatic amines that are produced by the action of ornithine decarboxylase (ODC) in a rate-limiting and protein kinase C (PKC)-regulated step. Because high levels of polyamines are found in the synovial fluid of arthritic patients, the aim of the present study was to identify the role of peripherally produced polyamines in a model of inflammatory pain induced by adjuvant. The subcutaneous injection of Complete Freund's adjuvant (CFA, 50 μL/paw) caused the development of mechanical allodynia and edema. Moreover, it increased ODC expression and activity and PKC activation. Administration of the selective ODC inhibitor DFMO (10 μmol/paw) attenuated the development of allodynia and edema and decreased ODC activity in both control and CFA-treated animals. Furthermore, administration of the PKC inhibitor GF109203X (1 nmol/paw) reduced allodynia and ODC activity in animals injected with CFA. A subcutaneous injection of putrescine (10 μmol/paw), spermidine (3–10 μmol/paw) or spermine (0.3–3 μmol/paw) into the rat paw also caused mechanical allodynia and edema. The present results suggest that endogenously synthesized polyamines are involved in the development of nociception and edema caused by an adjuvant. Moreover, polyamine production in inflammatory sites seems to be related to an increase in ODC activity stimulated by PKC activation. Thus, controlling polyamine synthesis and action could be a method of controlling inflammatory pain.

Aims: In the present work, we characterize the inflammatory process induced by the topical application of cinnamaldehyde on the skin of mice and verify the participation of transient receptor potential A1 TRPA1 receptors in this process. Main methods: We measured mouse ear edema and sensitization/desensitization after topical application of cinnamaldehyde or/and capsaicin. We also quantified cellular infiltration through myeloperoxidase (MPO) activity and histological and immunohistochemical analyses and evaluated the expression of TRPV1 and TRPA1 by western blot. Key findings: Cinnamaldehyde induced ear edema in mice (1-6 μg/ear) with a maximum effect of 4 μg/ear. Cinnamaldehyde promoted leukocyte infiltration as detected by increasing MPO activity and confirmed by histological analyses. The edema and cellular infiltration evoked by the application of 4 μg/ear of cinnamaldehyde were prevented by topical application of ruthenium red, a non-selective TRP antagonist as well as camphor and HC030031, two TRPA1 receptor antagonists. Cinnamaldehyde-induced edema, but not cellular infiltration, was prevented by topical application of the tachykinin NK1 antagonist, aprepitant, indicating a neuropeptide release phenomenon in this process. Additionally, we observed that repeated topical applications of cinnamaldehyde did not induce changes in sensitization or desensitization with respect to the edema response. Interestingly, repeated treatment with the TRPV1 agonist, capsaicin, abrogated it edematogenic response, confirming the desensitization process and partially decreasing the cinnamaldehyde-induced edema, suggesting the involvement of capsaicin-sensitive fibers. Significance: Our data demonstrate that the topical application of cinnamaldehyde produces an inflammatory response that is dependent on TRPA1 receptor stimulation.

Rationale: Spermidine (SPD) is an endogenous polyamine that modulates N-methyl-D-aspartate receptor functions, which has been reported to facilitate memory formation. Objectives: In the current study, we investigated the involvement of nitric oxide in the facilitatory effect of SPD on the memory of adult male Wistar rats in the inhibitory avoidance task. Results: The coadministration of the nonspecific NOS inhibitor N G nitro-L-arginine methyl ester (L-NAME) (0.1 nmol, intrahippocampus) with spermidine (0.2 nmol), immediately after training, prevented the memory improvement caused by spermidine in the avoidance inhibitory task. Spermidine increased nitrite and nitrate levels (NO X ) in the hippocampus 30 min after its administration, and L-NAME coinjection prevented the stimulatory effect of spermidine on NO X levels. The systemic injection of 7-nitroindazole (30 mg/kg, i.p.), 30 min before training, impaired memory and did not prevent spermidine-induced increase of NO X levels in the hippocampus. Conclusions: These results suggest that memory enhancement by spermidine is prevented by the nonspecific nitric oxide synthase inhibitor L-NAME.