Melatonin suppresses nitric oxide production in glial cultures by pro-inflammatory cytokines through p38 MAPK inhibition

Melatonin has been shown to down-regulate inflammatory responses and provide neuroprotection. However, the mechanisms underlying the anti-inflammatory properties of melatonin are poorly understood. In the present work, we studied the modulatory effect of melatonin against pro-inflammatory cytokines in glial cell cultures. Treatment with pro-inflammatory cytokines mainly tumor necrosis factor-alpha, interleukin 1-beta, and interferon-gamma induces an increase in inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production. Pre-treatment with melatonin produced an inhibitory effect on iNOS expression and NO production. The biochemical studies revealed that cytokine treatment favors the activation of several pathways, such as mitogen-activated protein kinases (MAPKs), STAT1, and STAT3; however, the anti-inflammatory effect of melatonin was accompanied only by a decrease in p38 MAPK activity. Likewise, SB203580 a p38 kinase inhibitor inhibits NO production. These data indicate that the anti-inflammatory action of melatonin in glial cells after stimulation with pro-inflammatory cytokines may be in part, attributable to p38 inhibition which down-regulates iNOS expression and NO production.

Lack of Jun-N-terminal kinase 3 (JNK3) does not protect against neurodegeneration induced by 3-nitropropionic acid

AIMS

3-Nitropropionic acid (3-NP) is a toxin that replicates most of the clinical and pathophysiological symptoms of Huntington's disease, inducing neurodegeneration in the striatum due to the inhibition of mitochondrial succinate dehydrogenase. Different pathways have been implicated in the cell death induced by 3-NP in rodents. One of them is the Jun-N-terminal kinase (JNK) pathway, which may play a role in the neurodegenerative process in different diseases. Moreover, the lack of one isoform of JNK (JNK3) has been associated with neuroprotection in different experimental models of neurodegeneration. Therefore, in the present study the role of JNK3 in the experimental Huntington's model induced by 3-NP administration was evaluated.

METHODS

3-NP was intraperitoneally administered once a day for 3 days to wild-type and Jnk3-null mice. Coronal brain sections were used to determine cell death and astrogliosis in striatum. Western blots were performed to determine the involvement of different pathways in both wild-type and Jnk3-null mice.

RESULTS

Although JNK activation was observed following 3-NP administration, the results indicate that the lack of JNK3 does not confer neuroprotection against 3-NP toxicity. Thus, other pathways must be involved in the neurodegeneration induced in this model. One of the possible pathways towards 3-NP-induced apoptosis could involve the calpains, as their activity was increased in wild-type and Jnk3-null mice.

CONCLUSION

Although JNK3 is a key protein involved in cell death in different neurodegenerative diseases, the present study demonstrates that the lack of JNK3 does not confer neuroprotection against 3-NP-induced neuronal death.

Taurine treatment inhibits CaMKII activity and modulates the presence of calbindin D28k, calretinin, and parvalbumin in the brain

Taurine, 2-aminoethanesulfonic acid, is present at high concentrations in many invertebrate and vertebrate systems and has several biological functions. In addition, it has been related to a neuroprotective role against several diseases such as epilepsy. In the present work, we treated mice with taurine and examined its effects on the expression of proteins in the hippocampus associated with calcium regulation. Taurine treatment alters the presence of calbindin-D28k, calretinin, and parvalbumin in the brain, mainly in the hippocampus. It also reduced CaMKII activity, indicating that taurine could alter calcium signaling pathways. However, the activity of calpain, a protease related to apoptosis induced by calcium signalling, did not change. The concentration of taurine in the hippocampus was also unaffected by the treatment. These results provide new insight into the role of taurine in calcium homeostasis.