Caffeic Acid Phenethyl Ester (CAPE) Protects PC12 Cells from Cisplatin-Induced Neurotoxicity by Activating the NGF-Signaling Pathway.

Cisplatin is a highly effective chemotherapeutic drug that is toxic to the peripheral nervous system. Findings suggest that axons are early targets of the neurotoxicity of cisplatin. Although many compounds have been reported as neuroprotective, there is no effective treatment against the neurotoxicity of cisplatin. Caffeic acid phenethyl ester (CAPE) is a propolis component with neuroprotective potential mainly attributed to antioxidant and anti-inflammatory mechanisms. We have recently demonstrated the neurotrophic potential of CAPE in a cellular model of neurotoxicity related to Parkinson's disease. Now, we have assessed the neurotrophic and neuroprotective effects of CAPE against cisplatin-induced neurotoxicity in PC12 cells. CAPE (10 µM) attenuated the inhibition of neuritogenesis and the downregulation of markers of neuroplasticity (GAP-43, synapsin I, synaptophysin, and 200-kD neurofilament) induced by cisplatin (5 µM). This concentration of cisplatin does not affect cell viability, and it was used in order to assess the early neurotoxic events triggered by cisplatin. When a lethal dose of cisplatin was used (IC50 = 32 µM), CAPE (10 µM) increased cell viability. The neurotrophic effect of CAPE is not dependent on NGF nor is it additive to the effect of NGF, but it might involve the activation of the NGF-high-affinity receptors (trkA). The involvement of other neurotrophin receptors such as trkB and trkC is unlikely. This is the first study to demonstrate the protective potential of CAPE against the neurotoxicity of cisplatin and to suggest the involvement of trkA receptors in the neuroprotective mechanism of CAPE. Based on these findings, the beneficial effect of CAPE on cisplatin-induced peripheral neuropathy should be further investigated.

The cannabinoid beta-caryophyllene (BCP) induces neuritogenesis in PC12 cells by a cannabinoid-receptor-independent mechanism.

Beta-caryophyllene (BCP) is a phytocannabinoid whose neuroprotective activity has been mainly associated with selective activation of cannabinoid-type-2 (CB2) receptors, inhibition of microglial activation and decrease of inflammation. Here, we addressed the potential of BCP to induce neuritogenesis in PC12 cells, a model system for primary neuronal cells that express trkA receptors, respond to NGF and do not express CB2 receptors. We demonstrated that BCP increases the survival and activates the NGF-specific receptor trkA in NGF-deprived PC12 cells, without increasing the expression of NGF itself. The neuritogenic effect of BCP in PC12 cells was abolished by k252a, an inhibitor of the NGF-specific receptor trkA. Accordingly, BCP did not induce neuritogenesis in SH-SY5Y neuroblastoma cells, a neuronal model that does not express trkA receptors and do not respond to NGF. Additionally, we demonstrated that BCP increases the expression of axonal-plasticity-associated proteins (GAP-43, synapsin and synaptophysin) in PC12 cells. It is known that these proteins are up-regulated by NGF in neurons and neuron-like cells, such as PC12 cells. Altogether, these findings suggest that BCP activates trka receptors and induces neuritogenesis by a mechanism independent of NGF or cannabinoid receptors. This is the first study to show such effects of BCP and their beneficial role in neurodegenerative processes should be further investigated.

Non-cytotoxic Concentration of Cisplatin Decreases Neuroplasticity-Related Proteins and Neurite Outgrowth Without Affecting the Expression of NGF in PC12 Cells.

Cisplatin is the most effective and neurotoxic platinum chemotherapeutic agent. It induces a peripheral neuropathy characterized by distal axonal degeneration that might progress to degeneration of cell bodies and apoptosis. Most symptoms occur nearby distal axonal branches and axonal degeneration might induce peripheral neuropathy regardless neuronal apoptosis. The toxic mechanism of cisplatin has been mainly associated with DNA damage, but cisplatin might also affect neurite outgrowth. Nevertheless, the neurotoxic mechanism of cisplatin remains unclear. We investigated the early effects of cisplatin on axonal plasticity by using non-cytotoxic concentrations of cisplatin and PC12 cells as a model of neurite outgrowth and differentiation. PC12 cells express NGF-receptors (trkA) and respond to NGF by forming neurites, branches and synaptic vesicles. For comparison, we used a neuronal model (SH-SY5Y cells) that does not express trkA nor responds to NGF. Cisplatin did not change NGF expression in PC12 cells and decreased neurite outgrowth in both models, suggesting a NGF/trkA independent mechanism. It also reduced axonal growth (GAP-43) and synaptic (synapsin I and synaptophysin) proteins in PC12 cells, without inducing mitochondrial damage or apoptosis. Therefore, cisplatin might affect axonal plasticity before DNA damage, NGF/trkA down-regulation, mitochondrial damage or neuronal apoptosis. This is the first study to show that neuroplasticity-related proteins might be early targets of the neurotoxic action of cisplatin and their role on cisplatin-induced peripheral neuropathy should be investigated in vivo.

The neuroprotection of cannabidiol against MPP⁺-induced toxicity in PC12 cells involves trkA receptors, upregulation of axonal and synaptic proteins, neuritogenesis, and might be relevant to Parkinson's disease.

Cannabidiol (CBD) is a non-psychoactive constituent of Cannabis sativa with potential to treat neurodegenerative diseases. Its neuroprotection has been mainly associated with anti-inflammatory and antioxidant events; however, other mechanisms might be involved. We investigated the involvement of neuritogenesis, NGF receptors (trkA), NGF, and neuronal proteins in the mechanism of neuroprotection of CBD against MPP(+) toxicity in PC12 cells. CBD increased cell viability, differentiation, and the expression of axonal (GAP-43) and synaptic (synaptophysin and synapsin I) proteins. Its neuritogenic effect was not dependent or additive to NGF, but it was inhibited by K252a (trkA inhibitor). CBD did not increase the expression of NGF, but protected against its decrease induced by MPP(+), probably by an indirect mechanism. We also evaluated the neuritogenesis in SH-SY5Y cells, which do not express trkA receptors. CBD did not induce neuritogenesis in this cellular model, which supports the involvement of trkA receptors. This is the first study to report the involvement of neuronal proteins and trkA in the neuroprotection of CBD. Our findings suggest that CBD has a neurorestorative potential independent of NGF that might contribute to its neuroprotection against MPP(+), a neurotoxin relevant to Parkinson's disease.

Caffeic acid phenethyl ester (CAPE) protects PC12 cells from MPP+ toxicity by inducing the expression of neuron-typical proteins.

Neurite loss is an early event in neurodegenerative diseases; therefore, the regeneration of the network of neurites constitutes an interesting strategy of treatment for such disorders. Neurotrophic factors play a critical role in neuronal regeneration, but their clinical use is limited by their inability to cross the blood brain barrier. Oxidative and inflammatory events are implicated in neurodegeneration and antioxidant compounds have been suggested as potential neuroprotectors. The protective potential of CAPE (caffeic acid phenethyl ester) has been shown in different models of neurotoxicity (in vitro and in vivo) and it has been associated with immune-modulatory, antioxidant and anti-inflammatory properties; however, other mechanisms might be involved. The present study demonstrates that CAPE protects PC12 cells from the cellular death induced by the dopaminergic neurotoxin MPP(+) by increasing the network of neurites. Results showed that CAPE induced the formation, elongation and ramification of neurites in PC12 cells non-stimulated with NGF (nerve growth factor) and inhibited the shortage of neurites induced by the dopaminergic neurotoxin. These effects were associated with increased expression of neuron-typical proteins responsible for axonal growth (GAP-43) and synaptogenesis (synaptophysin and synapsin I). It is noteworthy that, unlike neurotrophins, CAPE would be able to cross the blood brain barrier and exert its neurotrophic effects in the brain. This study corroborates the therapeutic potential of CAPE in neurodegenerative diseases while proposes the involvement of neuroplasticity in the mechanism of neuroprotection.

Cisplatin-induced nephrotoxicity and targets of nephroprotection: an update.

Cisplatin is a highly effective antitumor agent whose clinical application is limited by the inherent nephrotoxicity. The current measures of nephroprotection used in patients receiving cisplatin are not satisfactory, and studies have focused on the investigation of new possible protective strategies. Many pathways involved in cisplatin nephrotoxicity have been delineated and proposed as targets for nephroprotection, and many new potentially protective agents have been reported. The multiple pathways which lead to renal damage and renal cell death have points of convergence and share some common modulators. The most frequent event among all the described pathways is the oxidative stress that acts as both a trigger and a result. The most exploited pathways, the proposed protective strategies, the achievements obtained so far as well as conflicting data are summarized and discussed in this review, providing a general view of the knowledge accumulated with past and recent research on this subject.

Dimethylthiourea protects against mitochondrial oxidative damage induced by cisplatin in liver of rats.

Cisplatin is one of the most effective chemotherapeutic agents. However, at higher doses liver injury may occur. The purpose of this study was to explore whether the hydroxyl radical scavenger dimethylthiourea (DMTU) protects against cisplatin-induced oxidative damage in vivo and to define the mitochondrial pathways involved in cytoprotection. Adult male Wistar rats (200-220 g) were divided into four groups of eight animals each. The control group was treated only with an intraperitoneal (i.p.) injection of saline solution (1 ml/100 g body weight). The DMTU group was given only DMTU (500 mg/kg body weight, i.p), followed by 125 mg/kg body weight, i.p. (twice a day) until sacrifice. The cisplatin group was given a single injection of cisplatin (10 mg/kg body weight, i.p.). The DMTU+cisplatin group was given DMTU (500 mg/kg body weight, i.p.), just before the cisplatin injection (10 mg/kg body weight, i.p.), followed by injections of DMTU (125 mg/kg body weight, i.p.) twice a day until sacrifice (72 h after the treatment). DMTU did not present any direct effect on mitochondria and substantially inhibited cisplatin-induced mitochondrial damage in liver, therefore preventing elevation of AST and ALT serum levels. DMTU protected against (a) decreased hepatic ATP levels; (b) lipid peroxidation; (c) cardiolipin oxidation; (d) sulfhydryl protein oxidation; (e) mitochondrial membrane rigidification; (f) GSH oxidation; (g) NADPH oxidation; (h) apoptosis. Results suggest that antioxidants, particularly hydroxyl radical scavengers, protect liver mitochondria against cisplatin-induced oxidative damage. Several mitochondrial changes were delineated and proposed as interesting targets for cytoprotective strategy.

Mitochondrial uncoupling by the sulindac metabolite, sulindac sulfide.

Sulindac is a non-steroidal antiinflammatory drug (NSAID) known to inhibit cyclooxygenases (COX) 1 and 2, and at present of interest for cancer prevention. However, its therapeutic use has been limited by its toxicity to the gastrointestinal tract and liver. We address the effects of sulindac, of the pharmacologically inactive metabolite, sulindac sulfone, and of the pharmacologically active metabolite, sudindac sulfide, on isolated rat liver mitochondria and HepG2 cells. Sulindac sulfide, but not sulindac sulfone or sulindac itself, caused mitochondrial uncoupling, released preaccumulated Ca2+ from the organelle, and decreased Hep-G2 cell viability in apparent association with cell ATP depletion resulting from mitochondrial uncoupling-associated membrane potential dissipation.