Partial Protection of Paclitaxel-induced Neurotoxicity by Antioxidants

Abstract

Abstract. Background Paclitaxel is an anticancer drug that inhibits calcium-induced depolymerization of tubulin and thus blocks the progression of mitosis (1). It is clinically applied for the treatment of ovarian, breast, stomach and non-small cell lung cancer (2, 3). When used clinically, it causes severe side-effects such as leucopenia. thrombocytopenia, neutropenia and fatigue (4) and anorexia and constipation (5). Patients who received platinum treatment with a taxane were more likely to experience grade 2 to 4 neuropathy (6). Paclitaxel has been reported to induce oxidative stress in liver (slight, but no significant decrease in glutathione in liver) (7). Considering many beneficial effects of antioxidants under optimal conditions (usually achieved by adopting lower doses that stimulate growth) (8, 9), prevention of chemotherapeutic drug-induced neurotoxicity by antioxidants has been actively studied in recent years (10,11).In order to search for substances that reduce neurotoxicity induced by paclitaxel, we first investigated whether nerve growth factor (NGF)-induced differentiating rat neuronal cells (used as neuron model) are also very sensitive to paclitaxel, like malignant cells. The possible protective activity of four antioxidants, docosahexaenoic acid (DHA), acetyl-L-carnitine hydrochloride (ALC), N-acetyl-L-cysteine (NAC) and sodium ascorbate, against neurotoxicity of paclitaxel was then investigated. 745

Search of Neuroprotective Polyphenols Using the “Overlay” Isolation Method

“…We have previously reported that cisplatin showed potent cytotoxicity against differentiated PC12 cells [ 34 ], while taxanes (paclitaxel, docetaxel) and amyloid peptides (Aβ 1–42 , Aβ 25–35 ) showed cytostatic effects [ 34 , 35 ]. A cell sorter analysis demonstrated that cisplatin induced the apoptosis, characterized by the accumulation of the subG 1 population ( Figure 4 ).…”

“…Table 2 shows the SI (=CC 50 /EC 50 ) value of polyphenols, plant extracts and antioxidants, calculated using the data from our original papers [ 33 , 35 , 38 , 39 ] and the present study ( Table 2 ). The higher the SI value, the stronger the neuroprotective activity would be expected.…”

“…As a mechanism of neuronal protection, activation of the NF-E2 related factor 2 (Nrf2) pathway and the consequent upregulation of detoxification enzymes, such as heme-oxygenase-1 (HO-1), have been suggested [ 50 , 51 ]. However, we have recently reported that the neuroprotective activity of four antioxidants: Docosahexaenoic acid; acetyl- l -carnitine hydrochloride; N -acetyl- l -cysteine; and, sodium ascorbate, only partially protected PC12 cells from paclitaxel-induced toxicity [ 35 ]. Furthermore, it has recently been reported that neuronal protection caused by blackberry polyphenols is produced by mechanisms other than modulating reactive oxygen species (ROS) levels [ 52 ].…”

Change in Anticancer Drug Sensitivity During Neuronal Differentiation of PC12 Cells

“…The medium was completely removed by suction and replaced with 0.1 ml of differentiation medium (serum-free DMEM containing 50 ng/ml NGF). Cells were then incubated for 3 days to induce neuronal differentiation characterized by neurite formation (referred to as day 3 cells) ( Figure 1) (20). To induce more mature cells, cells were inoculated at 2×10 3 cells per microwell.…”

“…Differentiated cells were defined as the cells in which the extended neurites exceeded the longest diameter of each cell, assessed under a light microscope [EVOSfl; ThermoFisher Scientific, Waltham, MA, USA; described in Figure 1A of (21) After incubation for 48 h, the viable cell number was determined by MTT method. MTT concentration was reduced from 0.2 mg/ml to 0.1 mg/ml, due to its cytotoxicity towards neuronal cells (20). The cells were incubated for 1 h, and the formazan precipitate was dissolved in DMSO and the absorbance at 560 nm was measured (which reflects the relative viable cell number, more precisely cellular mitochondrial activity) with a plate leader (Infinite F 50 R;TECAN, Kawasaki, Japan).…”