NADPH oxidase has recently been identified as a promising new therapeutic target in ALS. Genetic deletion of NADPH oxidase (Nox2) in the transgenic SOD1(G93A) mutant mouse model of ALS was reported to increase survival remarkably by 97 days. Furthermore, apocynin, a widely used inhibitor of NADPH oxidase, was observed to dramatically extend the survival of the SOD1(G93A) ALS mice even longer to 113 days (Harraz et al. J Clin Invest 118: 474, 2008). Diapocynin, the covalent dimer of apocynin, has been reported to be a more potent inhibitor of NADPH oxidase. We compared the protection of diapocynin to apocynin in primary cultures of SOD1(G93A)-expressing motor neurons against nitric oxide-mediated death. Diapocynin, 10 μM, provided significantly greater protection compared to apocynin, 200 μM, at the lowest statistically significant concentrations. However, administration of diapocynin starting at 21 days of age in the SOD1(G93A)-ALS mouse model did not extend lifespan. Repeated parallel experiments with apocynin failed to yield protection greater than a 5-day life extension in multiple trials conducted at two separate institutions. The maximum protection observed was an 8-day extension in survival when diapocynin was administered at 100 days of age at disease onset. HPLC with selective ion monitoring by mass spectrometry revealed that both apocynin and diapocynin accumulated in the brain and spinal cord tissue to low micromolar concentrations. Diapocynin was also detected in the CNS of apocynin-treated mice. The failure to achieve significant protection with either apocynin or diapocynin raises questions about the utility for treating ALS patients.
"NOX2 expression is upregulated both in familial and sporadic ALS patients and in different ALS-animal models, and NOX2 inhibition by genetic ablation in SOD1-G93A mice significantly slows disease progression and extends survival (Wu et al., 2006; Marden et al., 2007). Pharmacological inhibition of NOX2 by apocynin was shown to protect motor neurons from mutant SOD1 toxicity in culture (Harraz et al., 2008; Marchetto et al., 2008; Trumbull et al., 2012), but gave contrasting results when administered to SOD1-G93A mice (Harraz et al., 2008; Trumbull et al., 2012). Anyway, NOX2 is considered one of the main markers of M1-toxic microglia. "
[Show abstract][Hide abstract] ABSTRACT: Rac1 is a major player of the Rho family of small GTPases that controls multiple cell signaling pathways, such as the organization of cytoskeleton (including adhesion and motility), cell proliferation, apoptosis and activation of immune cells. In the nervous system, in particular, Rac1 GTPase plays a key regulatory function of both actin and microtubule cytoskeletal dynamics and thus it is central to axonal growth and stability, as well as dendrite and spine structural plasticity. Rac1 is also a crucial regulator of NADPH-dependent membrane oxidase (NOX), a prominent source of reactive oxygen species (ROS), thus having a central role in the inflammatory response and neurotoxicity mediated by microglia cells in the nervous system. As such, alterations in Rac1 activity might well be involved in the processes that give rise to Amyotrophic Lateral Sclerosis (ALS), a complex syndrome where cytoskeletal disturbances in motor neurons and redox alterations in the inflammatory compartment play pivotal and synergic roles in the final disease outcomes. Here we will discuss the genetic and mechanistic evidence indicating the relevance of Rac1 dysregulation in the pathogenesis of ALS.
"This study shows that orally administered apocynin can build up a sufficiently high concentration within the CNS parenchyma for mitigating neurotoxic levels of ROS production. However, these promising data could not be reproduced in another study using the same mutant mouse strain . "
[Show abstract][Hide abstract] ABSTRACT: Accumulating evidence suggests that inflammatory mediators secreted by activated resident or infiltrated innate immune cells have a significant impact on the pathogenesis of neurodegenerative diseases. This may imply that patients affected by a neurodegenerative disease may benefit from treatment with selective inhibitors of innate immune activity. Here we review the therapeutic potential of apocynin, an essentially nontoxic phenolic compound isolated from the medicinal plant
. Apocynin is a selective inhibitor of the phagocyte NADPH oxidase Nox2 that can be applied orally and is remarkably effective at low dose.
BioMed Research International 07/2014; 2014(5):298020. DOI:10.1155/2014/298020 · 3.17 Impact Factor
"On the other hand, another study has shown that after the chronic treatment with apocynin (150 mg/kg in the drinking water for 100 days), micromolar concentrations of diapocynin were found accumulated in the brain tissue of transgenic SOD1 mutant mice. Its content represented about 7-8% of the total apocynin concentration . Although there are some experimental evidence describing the neuroprotective effects of apocynin under different models of PD [12, 30, 31], more detailed studies elucidating the production of diapocynin in brain structures affected by this neurodegenerative condition are needed to elucidate whether these promising findings are related to Nox inhibition rather than apocynin antioxidant effects. "
[Show abstract][Hide abstract] ABSTRACT: Several lines of investigation have implicated oxidative stress in Parkinson's disease (PD) pathogenesis, but the mechanisms involved are still unclear. In this study, we characterized the involvement of NADPH oxidase (Nox), a multisubunit enzyme that catalyzes the reduction of oxygen, in the 6-hydroxydopamine- (6-OHDA-) induced PD mice model and compared for the first time the effects of this neurotoxin in mice lacking gp91(phox-/-), the catalytic subunit of Nox2, and pharmacological inhibition of Nox with apocynin. Six-OHDA induced increased protein expression of p47(phox), a Nox subunit, in striatum. gp91(phox-/-) mice appear to be completely protected from dopaminergic cell loss, whereas the apocynin treatment conferred only a limited neuroprotection. Wt mice treated with apocynin and gp91(phox-/-) mice both exhibited ameliorated apomorphine-induced rotational behavior. The microglial activation observed within the striatum and the substantia nigra pars compacta (SNpc) of 6-OHDA-injected Wt mice was prevented by apocynin treatment and was not detected in gp91(phox-/-) mice. Apocynin was not able to attenuate astrocyte activation in SN. The results support a role for Nox2 in the 6-OHDA-induced degeneration of dopaminergic neurons and glial cell activation in the nigrostriatal pathway and reveal that no comparable 6-OHDA effects were observed between apocynin-treated and gp91(phox-/-) mice groups.
Oxidative Medicine and Cellular Longevity 11/2013; 2013(3):157857. DOI:10.1155/2013/157857 · 3.36 Impact Factor
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