Menadione‐induced caspase‐dependent programmed cell death in the green chlorophyte Chlamydomonas reinhardtii

Abstract

Menadione, a quinone that undergoes redox cycles leading to the formation of superoxide radicals, induces programmed cell death (PCD) in animals and plants. In this study, we investigated whether the unicellular green alga Chlamydomonas reinhardtii P.A.Dangeard is capable of executing PCD upon exposure to menadione stress. We report here, the morphological, molecular, and biochemical changes after menadione exposure of C. reinhardtii cells. The effect of menadione on cell death has been shown to be dose-dependent; 5-100 μM menadione causes 20%-46% cell death, respectively. It appears that growth is inhibited with the concomitant degradation of the photosynthetic pigments and by a decrease in the photosynthetic capacity. Being an oxidative stress, we found an H2 O2 burst within 15 min of menadione exposure, followed by an increase in antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], and ascorbate peroxidase [APX]) activities. In parallel, RT-PCR was performed for transcript analyses of Mn-SOD, CAT, and APX. Our results clearly revealed that expression of these genes were up-regulated upon menadione exposure. Furthermore, classical hallmarks of PCD such as alteration of mitochondrial membrane potential, significant increase in caspase-3-like DEVDase activity, cleavage of poly (ADP) ribose polymerase (PARP)-1-like enzyme, and DNA fragmentation as detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and oligosomal DNA fragmentation were observed. Moreover, antibodies against a mammalian active caspase-3 shared epitopes with a caspase-3-like protein of ~17 kDa; its pattern of expression and activity correlated with the onset of cell death. To the best of our knowledge, this is the first report on menadione-induced PCD through a mitochondrian-caspase protease pathway in an algal species.

Unravelling the inhibitory activity of Chlamydomonas reinhardtii sulfated polysaccharides against α-Synuclein fibrillation

“…Cells were grown and maintained by periodic transfers in Tris Acetate Phosphate (TAP; pH 7) as mentioned by Sirisha et al . 62 .…”

Menadione perturbs oxidative stress biomarkers and testicular function indices of rats

“…Menadione multiorgan toxicity is associated with overwhelmed antioxidant defense resulting from overproduction of •O 2 − and H 2 O 2 . Interestingly, studies have reported a nexus between oxidative stress and testicular toxicity .…”

“…In the presence of Fe 2+ , H 2 O 2 produced is converted to •OH via Fenton reaction . All these culminate to oxidative stress associated with menadione toxicity and is further aggravated by glutathione depletion . Furthermore, apoptosis, mitochondrial dysfunction, and DNA fragmentation are also associated with menadione toxicity …”

The Cytotoxic Effects of Camptothecin and Mastoparan on the Unicellular Green Alga Chlamydomonas reinhardtii

“…During the last decade, several authors have reported evidence for the occurence of apoptosis in the unicellular green alga C. reinhardtii (Moharikar et al 2006;Sirisha et al 2014;Yordanova et al 2010Yordanova et al , 2013Zuo et al 2012).…”