Elsevier

Neurotoxicology and Teratology

Volume 68, July–August 2018, Pages 72-83
Neurotoxicology and Teratology

In vitro protective activity of South Australian marine sponge and macroalgae extracts against amyloid beta (Aβ1–42) induced neurotoxicity in PC-12 cells

https://doi.org/10.1016/j.ntt.2018.05.002Get rights and content

Highlights

  • 60% of South Australian marine sponge extracts demonstrated cytotoxicity.

  • Brown algae demonstrated the least cytotoxicity among other algae classes.

  • About 31.5% of extract demonstrated neuroprotective activities.

Abstract

South Australia is a biodiversity hotspot of marine sponges and macroalgae. This study aimed to evaluate the potential neuroprotective activity of extracts from these two marine sources by reducing the toxicity of human amyloid beta Aβ1–42 in a cell model assay using PC-12 cells. A total of 92 extracts (43, 13, 16, and 20 extracts from sponge of 8 orders and 17 families, green algae of 3 orders and 4 families, brown algae of 6 orders and 8 families, and red algae of 5 orders and 10 families, respectively) were initially screened at three different concentrations (0.25, 2.5 and 25 μg/mL) to evaluate their toxicity using the MTT assay. About half of these extracts (26, 6, 5, and 10 extracts from sponge, green algae, brown algae, and red algae, respectively) showed some cytotoxicity, and were hence excluded from further assays. The rest of extracts (45 extracts in total) at 0.25 and 25 μg/mL were subsequently screened in a neuroprotection assay against Aβ1–42 cytotoxicity. A cell viability reduction of 30% was observed in the MTT assay when the cells were treated with 1 μM Aβ1–42. 29 extracts (13, 4, 7, and 5 extracts from sponge, green algae, brown algae, and red algae, respectively) reduced the toxicity induced by Aβ1–42 (P < 0.05), indicating neuroprotective activity. These results demonstrate that marine sponge and macroalgae form a broad spectrum are promising sources of neuroprotective compounds against the hallmark neurotoxic protein in Alzheimer's disease (AD).

Introduction

Alzheimer's disease (AD) is a neurodegenerative disease responsible for 60–80% of dementia cases (Alzheimer'sAssociation, 2014). Current treatment strategies for AD mostly target acetylcholinesterase and the N-methyl-d-aspartate (NMDA) receptor. However, these treatments can only mitigate some of the cognitive and memory loss symptoms and are not considered disease-modifying. Hence, the development of new treatments for AD are required (Scarpini et al., 2003).

One of the main hallmarks of AD is the presence of amyloid beta (Aβ) protein that forms plaques in the brain. Aβ1–40 and Aβ1–42 are major forms generated from the cleavage of amyloid precursor protein (APP) by β-secretase and γ-secretase (Hussain et al., 1999). It is suggested that the aggregation and diminished clearance are pathogenic factors of AD (Hardy and Selkoe, 2002). Animal studies demonstrate that amyloid plaques are correlated with memory defects (Hsiao et al., 1996). For that reason, targeting Aβ may be considered an effective approach in the treatment of AD (Hardy and Selkoe, 2002).

Marine sponges, one of the oldest multicellular animals on the planet (Hentschel et al., 2002), are a rich source of natural compounds contributing >30% of all compounds discovered from marine organisms (Mehbub et al., 2014). These compounds possess a spectrum of biological activities including anti-viral, anti-bacterial, and anti-inflammatory properties (Mayer et al., 2013). A recent review of neuroprotective compounds from marine sponges ascribed a variety of mechanisms to their neuroprotection, including glutamate and serotoninergic receptor activity, kinase inhibition, neuritogenic and anti-oxidant activity (Alghazwi et al., 2016a). Interestingly, seven out of 90 neuroprotective compounds were reported as sourced from Australian species.

Macroalgae (or seaweeds) have been known for their uses in food and as potential drug sources. Macroalgae can be classified based on the pigment colours into different phyla such as Chlorophyta, Ochrophyta (class Phaeophyceae), and Rhodophyta which are commonly named as the green, brown and red algae, respectively (Lobban and Harrison, 1994; Guiry, 2012). Macroalgae present a range of biological activities such as anti-viral, anti-bacterial, antioxidant, anti-cancer and neuroprotective activity (Wang et al., 2008; Lima-Filho et al., 2002; Kang et al., 2003; Kang et al., 2004; Aisa et al., 2005; Pangestuti and Kim, 2011). A recent review reported a total of 99 compounds isolated from macroalgae demonstrating neuroprotective activities (Alghazwi et al., 2016b). The mechanisms ascribed to these effects included inhibiting Aβ aggregation and acetylcholinesterase inhibition, decreasing oxidative stress and kinase activity, enhancing neurite outgrowth, anti-inflammatory activity and protecting dopaminergic neurons.

South Australian waters have >1000 different species of sponges that belong to 200 genera (Bergquist and Skinner, 1982). South Australia hosts one of the highest diversity of macroalgae, as it is home to over 1200 species with 62% of them as endemic (Phillips, 2001; Womersley, 1996). Few studies have reported neuroprotective activities of sponges and macroalgae collected in Australian waters, with only seven neuroprotective compounds from sponges. Esmodil was shown to inhibit acetylcholinesterase (Capon et al., 2004), while debromohymenialdisine inhibited CDK5/p25, CK1, and GSK-3β (Zhang et al., 2012c). Four compounds (Lamellarins O1, Ianthellidone F, lamellarins O2 and O) were shown to inhibit β-site amyloid precursor protein cleaving enzyme (BACE) (Zhang et al., 2012a), in addition to Dictyodendrin J (Zhang et al., 2012b). Moreover, only 3 compounds isolated from macroalgae collected in Australia were shown to have demonstrated neuroprotective activity. Spiralisone A, spiralisone B, and chromone 6 showed inhibition of CDK5/p25, CK1δ and GSK3β kinases (Zhang et al., 2012d). Therefore the present study was conducted to evaluate the potential of South Australia marine sponge and macroalgae extracts as a source of neuroprotective compounds, with a focus on reducing the cytotoxicity of Aβ in neuronal PC-12 cells.

Section snippets

Samples collection

The Australian Institute of Marine Science (AIMS) provided all the samples used in this study. These samples were collected by hand whilst scuba diving or from shallows at low tide. They were frozen after a representative taxonomy sample was taken. All samples were collected in South Australia. The details of collections sites can be found in the Table 1.

The taxonomy information was provided by AIMS. Phylogenetic trees of these samples were conducted according to their class, order, family,

Cytotoxicity of extracts of marine sponges and macroalgae from South Australia

The cytotoxicity of 93 marine extract samples were screened against PC-12 cells using the MTT assay at three different extract concentrations (0.25, 2.5, and 25 μg/mL). The results were analysed to determine which extracts did not kill >10% of cells in any concentration. Table 2, Table 3, Table 4, Table 5 shows the cytotoxicity screening results after treating with marine sponge extracts, green algae, brown algae and red algae, respectively. Twenty six out of 43 sponge extracts, six out of 13

Discussion

60% of the marine sponge extracts tested (26 out of 43 extracts) at a concentration range of 0.25-25 μg/mL were cytotoxic to PC-12 cells (Table 6). Cytotoxic compounds in sponges are common given that half of the anticancer compounds discovered during 2001 to 2010 were isolated from sponges (Mehbub et al., 2014). In addition, a study showed that four dictyodendrins isolated from Ianthella sp. were shown to be active in reducing the activity of beta-site amyloid precursor protein cleaving enzyme

Conclusion

This study has demonstrated that marine sponges and macroalgae collected in South Australia are a potential source of neuroprotective compounds, with one-third of 92 extracts screened (29 extracts) found to reduce neurotoxicity induced by Aβ in PC-12 cells. More than half of these extracts (15 extracts out of 29 extracts) were active in both tested concentrations. 65% of these sponge and macroalgae extracts from genus that have not been reported before, to demonstrate protection against

Conflict of interest

The authors confirm that this article content has no conflict of interest.

Transparency document

Transparency document.

Acknowledgements

Flinders University (ARC Linkage Grant LP 150100225) has provided the research support to this project, and the Ministry of Higher Education in Saudi Arabia for their scholarship support to Mousa Alghazwi. The authors would like to acknowledge The Australian Institute of Marine Science (AIMS) for providing all the marine samples. Also, special thanks to Philip Kearns from AIMS and Moana Simpson from Compounds Australia.

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