Widespread cerebral deposition of a 40 -43-amino acid peptide called the amyloid ␤-protein (A␤) in the form of amyloid fibrils is one of the most prominent neuropathologic features of Alzheimer's disease. Numerous studies suggest that A␤ is toxic to neurons by free radical-mediated mechanisms. We have previously reported that melatonin prevents oxidative stress and death of neurons exposed to A␤. In the process of screening indole compounds for neuroprotection against A␤, potent neuroprotective properties were uncovered for an endogenous related species, indole-3-propionic acid (IPA). This compound has previously been identified in the plasma and cerebrospinal fluid of humans, but its functions are not known. IPA completely protected primary neurons and neuroblastoma cells against oxidative damage and death caused by exposure to A␤, by inhibition of superoxide dismutase, or by treatment with hydrogen peroxide. In kinetic competition experiments using free radical-trapping agents, the capacity of IPA to scavenge hydroxyl radicals exceeded that of melatonin, an indoleamine considered to be the most potent naturally occurring scavenger of free radicals. In contrast with other antioxidants, IPA was not converted to reactive intermediates with pro-oxidant activity. These findings may have therapeutic applications in a broad range of clinical situations.Brains of patients afflicted with Alzheimer's disease show abnormal expression of numerous oxidative stress indicators (1-5) as well as extensive evidence of oxidative damage to proteins (6) and nucleic acids (7,8). A prominent feature of the Alzheimer's disease brain is the widespread cerebral deposition of a 40 -43-amino acid peptide called the amyloid ␤-protein (A␤) 1 in the form of amyloid fibrils within senile plaques and in cerebral and meningeal blood vessels (9, 10). A large body of data suggests that A␤ causes neuronal degeneration and death by mechanisms that involve reactive oxygen species reviewed in Ref. 15).Since the severity of the dementia in Alzheimer's disease has been correlated best with the extent of synaptic loss and the degree of neuronal death (16, 17), enhancing neuronal survival has been a primary objective of many therapeutic strategies. We have recently reported that melatonin prevents oxidative stress and death of neurons exposed to the amyloid peptide (18,19). In the process of screening indole compounds as neuroprotective agents, new properties were uncovered for an endogenous species, indole-3-propionic acid (IPA). IPA has previously been identified in the plasma and cerebrospinal fluid of humans, but its functions are not known (20,21). IPA has, like melatonin, a heterocyclic aromatic ring structure with high resonance stability, which led us to suspect similar neuroprotective and antioxidant properties. Here, we report that IPA prevented oxidative stress and death of primary neurons and neuroblastoma cells exposed to A␤. In addition, IPA also showed a strong level of neuroprotection in two other paradigms of oxidative stress. We found...

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Increased levels of a 40-42 amino-acid peptide called the amyloid b protein (Ab) and evidence of oxidative damage are early neuropathological markers of Alzheimer's disease (AD). Previous investigations have demonstrated that melatonin is decreased during the aging process and that patients with AD have more profound reductions of this hormone. It has also been recently shown that melatonin protects neuronal cells from Ab-mediated oxidative damage and inhibits the formation of amyloid fibrils in vitro. However, a direct relationship between melatonin and the biochemical pathology of AD had not been demonstrated. We used a transgenic mouse model of Alzheimer's amyloidosis and monitored over time the effects of administering melatonin on brain levels of Ab, abnormal protein nitration, and survival of the mice. We report here that administration of melatonin partially inhibited the expected time-dependent elevation of b-amyloid, reduced abnormal nitration of proteins, and increased survival in the treated transgenic mice. These findings may bear relevance to the pathogenesis and therapy of AD.

Exposure of neuronal cells to the Alzheimer's amyloid beta protein (Abeta) results in extensive oxidative damage of bio-molecules that are profoundly harmful to neuronal homeostasis. It has been demonstrated that melatonin protects neurons against Abeta-mediated neurotoxicity, including cell death and a spectrum of oxidative lesions. We undertook the current study to determine whether melatonin membrane receptors are involved in the mechanism of neuroprotection against Abeta neurotoxicity. For this purpose, we characterized the free-radical scavenging potency of several compounds exhibiting various affinities for melatonin membrane receptors (MLT 1a and 1b). Abeta-mediated neurotoxicity was assessed in human neuroblastoma cells and in primary hippocampal neurons. In sharp contrast with melatonin, no neuroprotection against Abeta toxicity was observed when we used melatonin membrane receptor agonists that were devoid of antioxidant activity. In contrast, the cells were fully protected in parallel control experiments when either melatonin, or the structurally unrelated free-radical scavenger phenyl-N-t-butyl nitrone (PBN), were added to Abeta-containing culture media. This study demonstrates that the neuroprotective properties of melatonin against Abeta-mediated toxicity does not require binding of melatonin to a membrane receptor and is likely the result of the antioxidant and antiamyloidogenic features of the agent.

Dendritic cell (DC) vaccines are a newly emerging immunotherapeutic approach for the treatment and prevention of cancer, but major challenges still remain particularly with respect to clinical efficacy. Engineering and optimization of adjuvant formulations for DC-based vaccines is one strategy through which more efficacious treatments may be obtained. In this study, we developed a new ex vivo approach for DC vaccine preparation. We evaluated two highly purified mixed polysaccharide fractions from the root of Astragalus membranaceus and Codonopsis pilosulae, named Am and Cp, for their use in enhancing the efficiency of a DC-based cancer vaccine against metastasis of 4T1 mammary carcinoma in mice. Mixed lymphocyte reaction showed all Am-, Cp- and [Am+Cp]-treated DCs enhanced mouse CD4+ and CD8+ T-cell proliferation. [Am+Cp]-treated DCs exhibited the strongest anti-4T1 metastasis activity in test mice. Treatments with Am, Cp and [Am+Cp] also resulted in augmented expression of CD40, CD80 and CD86 markers in test DCs. Bioinformatics analysis of the cytokine array data from treated DCs identified that [Am+Cp] is efficacious in activation of specific immune functions via mediating the expression of cytokines/chemokines involved in the recruitment and differentiation of defined immune cells. Biochemical analysis revealed that Am and Cp are composed mainly of polysaccharides containing a high level (70–95%) glucose residues, but few or no (< 1%) mannose residues. In summary, our findings suggest that the specific plant polysaccharides Am and Cp extracted from traditional Chinese medicines can be effectively used instead of bacterial LPS as a potent adjuvant in the formulation of a DC-based vaccine for cancer immunotherapies.