Neoechinulin A

Neoechinulin a impedes the progression of rotenone-induced cytotoxicity in PC12 cells.[Pubmed:21415535]

Biol Pharm Bull. 2011;34(2):243-8.

Neoechinulin A, an indole alkaloid from marine fungi, can protect PC12 cells from the cytotoxicity of 1-methyl-4-phenylpyridinium (MPP(+)), a Parkinson disease-inducing neurotoxin, by ameliorating downstream events resulting from mitochondrial complex I inactivation. However, the cytoprotective mechanisms remained unclear. In this study, by using rotenone, another parkinsonian-inducing neurotoxin targeting mitochondrial complex I, we investigated the cytoprotective mechanism of Neoechinulin A. Rotenone-induced cell death was associated with accelerated glucose consumption, and excess glucose supplementation in the culture medium almost completely suppressed cell death, suggesting that glucose deficiency in the medium is critical for triggering cell death in this model. Co-treatment with Neoechinulin A, but not Neoechinulin A pre-treatment before rotenone exposure, significantly impeded cell death by rotenone. Although the presence of Neoechinulin A did not affect the accelerated glycolytic turnover in rotenone-treated cells, it paradoxically decreased ATP levels in the cells, suggesting increased ATP consumption. Although the link between the decreased ATP levels and cytoprotection is not clear at present, it suggests that Neoechinulin A may ameliorate rotenone toxicity by activating a cytoprotective machinery that requires ATP.

Anti-inflammatory effect of neoechinulin a from the marine fungus Eurotium sp. SF-5989 through the suppression of NF-small ka, CyrillicB and p38 MAPK Pathways in lipopolysaccharide-stimulated RAW264.7 macrophages.[Pubmed:24165583]

Molecules. 2013 Oct 25;18(11):13245-59.

In the course of a bioassay-guided study of metabolites from the marine fungus Eurotium sp. SF-5989, two diketopiperazine type indole alkaloids, neoechinulins A and B, were isolated. In this study, we investigated the anti-inflammatory effects of neoechinulins A (1) and B (2) on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Neoechinulin A (1) markedly suppressed the production of nitric oxide (NO) and prostaglandin E2 (PGE2) and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose dependent manner ranging from 12.5 microM to 100 microM without affecting the cell viability. On the other hand, neoechinulin B (2) affected the cell viability at 25 microM although the compound displayed similar inhibitory effect of NO production to Neoechinulin A (1) at lower doses. Furthermore, Neoechinulin A (1) decreased the secretion of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta). We also confirmed that Neoechinulin A (1) blocked the activation of nuclear factor-kappaB (NF-kappaB) in LPS-stimulated RAW264.7 macrophages by inhibiting the phosphorylation and degradation of inhibitor kappa B (IkappaB)-alpha. Moreover, Neoechinulin A (1) decreased p38 mitogen-activated protein kinase (MAPK) phosphorylation. Therefore, these data showed that the anti-inflammatory effects of Neoechinulin A (1) in LPS-stimulated RAW264.7 macrophages were due to the inhibition of the NF-kappaB and p38 MAPK pathways, suggesting that Neoechinulin A (1) might be a potential therapeutic agent for the treatment of various inflammatory diseases.

Neoechinulin a imparts resistance to acute nitrosative stress in PC12 cells: a potential link of an elevated cellular reserve capacity for pyridine nucleotide redox turnover with cytoprotection.[Pubmed:22791159]

Biol Pharm Bull. 2012;35(7):1105-17.

Treatment of PC12 cells with fungus-derived alkaloid Neoechinulin A for more than 12 h renders the cells resistant to subsequent superoxide (O(2)(-))/nitric oxide (NO) insults derived from 3-morpholinosydnonimine (SIN-1). However, the underlying mechanism(s) remains largely unclear. To elucidate the mechanism(s), we assessed the specificity of the cytoprotection afforded by Neoechinulin A treatment using other cytocidal stressors and also clarified the resulting cellular alterations, focusing on the antioxidant and metabolic enzymes systems. Neoechinulin A treatment for more than 12 h endowed PC12 cells with significant resistance to transient NO toxicity, but not persistent NO toxicity, bolus H(2)O(2) toxicity, or oxidative insult from the redox cycling quinone menadione. Cellular antioxidant system profiling revealed no substantial potentiation of the activity of any antioxidant enzyme in lysate from the Neoechinulin A-treated cells excluding glutathione (GSH) content, which was significantly decreased (>50%), resulting in a proportional compromise in the thiol-reducing activity of the intact cells. In addition, no differences were observed in the activity for any nicotinamide adenine dinucleotide (phosphate) reduced form (NAD(P)H)-generating enzyme, steady-state NAD(P)H/nicotinamide adenine dinucleotide (phosphate) oxidized form (NAD(P)(+)) ratios, or the levels of total NAD(P)H. Nevertheless, the Neoechinulin A-treated intact cells exhibited increased NAD(P)H redox turnover when driven by extracellular tetrazolium. The structurally inactive analog preechinulin failed to protect cells against NO toxicity or induce these alterations, suggesting their link with the cytoprotective mechanism. These results suggest that Neoechinulin A, despite disabling the GSH defense system, confers cytoprotection against nitrosative stresses by elevating the cellular reserve capacity for NAD(P)H generation, which could offset crippling of energy-supplying systems due to nitrosative stress.

Structure-activity relationships of neoechinulin A analogues with cytoprotection against peroxynitrite-induced PC12 cell death.[Pubmed:17965477]

J Antibiot (Tokyo). 2007 Oct;60(10):614-21.

Neoechinulin A, an alkaloid from Eurotium rubrum Hiji025, protected neuronal PC12 cells against cell death induced by peroxynitrite derived from SIN-1 (3-(4-morpholinyl)sydnonimine hydrochloride). In this study, we investigated the structure-activity relationships of Neoechinulin A and a set of its analogues by using assays to measure anti-nitration and antioxidant activities and cytoprotection against SIN-1-induced PC12 cell death. The presence of the diketopiperazine ring was essential for both the antioxidant and anti-nitration activities of Neoechinulin A derivatives. Nevertheless, a derivative lacking the diketopiperazine ring could still protect PC12 cells against SIN-1 cytotoxicity. An acyclic analogue completely lost the cytoprotective effect while retaining its antioxidant/anti-nitration activities. Pre-incubation of the cells with Neoechinulin A for at least 12 hours was essential for the cells to gain SIN-1 resistance. These results suggest that Neoechinulin A endows the cells with cytoprotection through a biological effect different from the apparent antioxidant/anti-nitration activities.

Neoechinulin A suppresses amyloid-beta oligomer-induced microglia activation and thereby protects PC-12 cells from inflammation-mediated toxicity.[Pubmed:23261590]

Neurotoxicology. 2013 Mar;35:30-40.

A pathological hallmark of Alzheimer's disease (AD), aggregation and deposition of amyloid-beta peptides, has been recognized as a potent activator of microglia-mediated neuroinflammation and neuronal dysfunction. Therefore, downregulation of microglial activation has a significant therapeutic demand. In this study, focus was given to evaluate the ability of Neoechinulin A, an indole alkaloid isolated from marine-derived Microsporum sp., to attenuate microglial activation by oligomeric amyloid-beta 1-42 (Abeta42). Neoechinulin A treatment significantly inhibited the generation of reactive oxygen and nitrogen species in Abeta42-activated BV-2 microglia cells. In addition, we found that Neoechinulin A significantly suppressed the production of neurotoxic inflammatory mediator tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and prostaglandin E2 (PGE2) in activated BV-2 cells. Moreover, the treatment downregulated the protein and gene expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-alpha, IL-1beta and IL-6. Further, activated microglia-mediated apoptosis of PC-12 pheochromocytoma cells was significantly repressed by Neoechinulin A. The molecular mechanism studies suggested that Neoechinulin A may block the phosphorylation of mitogen-activated protein kinase (MAPK) molecule p38, apoptosis signal-regulating kinase 1 (ASK-1) and nuclear translocation of nuclear factor-kappaB (NF-kappaB) p65 and p50 subunits. Regulation of these signalling pathways have most probably contributed to the anti-inflammatory activity of Neoechinulin A. Collectively, these results suggest that with further studies Neoechinulin A have a potential to be developed as a modulator of neuroinflammatory process in AD.