Lignosus rhinocerotis (Cooke) Ryvarden mimics the neuritogenic activity of nerve growth factor via MEK/ERK1/2 signaling pathway in PC-12 cells

Abstract

The traditional application of the sclerotium of Lignosus rhinocerotis (tiger’s milk mushroom) by the indigenous folks as tonic and remedy to treat a variety of ailments has been documented in Malaysia. Indigenous communities claimed to have consumed the decoction to boost their alertness during hunting. Mental alertness is believed to be related to neuronal health and neuroactivity. In the present study, the cell viability and neuritogenic effects of L. rhinocerotis sclerotium hot aqueous and ethanolic extracts, and crude polysaccharides on rat pheochromocytoma (PC-12) cells were studied. Interestingly, the hot aqueous extract exhibited neuritogenic activity comparable to NGF in PC-12 cells. However, the extracts and crude polysaccharides stimulated neuritogenesis without stimulating the production of NGF in PC-12 cells. The involvements of the TrkA receptor and MEK/ERK1/2 pathway in hot aqueous extract-stimulated neuritogenesis were examined by Trk (K252a) and MEK/ERK1/2 (U0126 and PD98059) inhibitors. There was no significant difference in protein expression in NGF- and hot aqueous extract-treated cells for both total and phosphorylated p44/42 MAPK. The neuritogenic activity in PC-12 cells stimulated by hot aqueous and ethanolic extracts, and crude polysaccharides of L. rhinocerotis sclerotium mimicking NGF activity via the MEK/ERK1/2 signaling pathway is reported for the first time.

A Status Review of the Bioactive Activities of Tiger Milk Mushroom Lignosus rhinocerotis (Cooke) Ryvarden

“…According to the studies by Seow et al ( 2013a , 2015 ), the maximal neuritogenic activity in PC12 at 25 μg/mL of aqueous extract was 20.99% followed by ethanolic extract (17.4%) and crude polysaccharides (16.4%). The hot aqueous extract (25 μg/mL) stimulated neuritogenesis as equivalent to NGF (50 μg/mL).…”

“…On the other hand, the ethyl acetate and n-butanol fractions of L. rhinocerotis were found to mimic the neuritogenic activity of NGF by targeting the TrkA receptor and activated the mammalian target of rapamycin (mTOR) signaling pathway with the phosphorylation of the transcription factors, cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), and leading to the increased expressions of neuritogenesis biomarker, i.e., the growth associated protein 43 (GAP43), tubulin alpha 4A (TUBA4A), and tubulin beta 1 (TUBB1) in PC12 cells (Seow, 2016 ).…”

“…Eik et al ( 2012 ) and Seow et al ( 2015 ) reported that the aqueous and ethanol extracts of the L. rhinocerotis sclerotium were non-cytotoxic to PC12 cells after 48 h incubation. Phan et al ( 2013 ) also reported that the aqueous extracts of the mycelium and sclerotium of L. rhinocerotis were not cytotoxic with IC 50 values of 1.75–5.93 mg/mL to mouse embryonic fibroblasts (BALB/3T3) and N2a cells after 24 h incubation.…”

Signaling pathways involved in HSP32 induction by hyperbaric oxygen in rat spinal neurons

“…Although U0126 is frequently used as an ERK1/2 inhibitor, its actual target is mitogen-activated and extracellular signal-regulated kinase 1/2 (MEK1/2), simply because MEK1/2-ERK1/2 is generally considered an integrated signal pathway [26] , [27] , while SCH772984 is a direct inhibitor to ERK1/2. To confirm the involvement of MEK1/2 in HBO induced HSP32 expression, the activation of MEK1/2 at 0, 0.5, 1, 2 and 4 h following HBO exposure and the effects of another MEK1/2 inhibitor trametinib or MEK1/2 knockdown were observed.…”

“…The existing data showed that activation of ERK1/2 played a mostly positive role in the regulation of HSP32 [25] , [39] , and ERK1/2 is the only known physiological substrates of MEK1/2 [26] . U0126 is a specific inhibitor of MEK1/2 and is commonly used to inhibit the activation of the MEK1/2-ERK1/2 cascade [27] , [40] . As far as we know, this is the first finding that MEK1/2 may work via pathways other than ERK1/2.…”