Increased In Vitro Lysosomal Function in Oxidative Stress-Induced Cell Lines

Abstract

Exposure of mammalian cells to oxidative stress alters lysosomal enzymes. Through cytochemical analysis of lysosomes with LysoTracker, we demonstrated that the number and fluorescent intensity of lysosome-like organelles in HeLa cells increased with exposure to hydrogen peroxide (H₂O₂), 6-hydroxydopamine (6-OHDA), and UVB irradiation. The lysosomes isolated from HeLa cells exposed to three oxidative stressors showed the enhanced antimicrobial activity against Escherichia coli. Further, when lysosomes that were isolated from HeLa cells exposed by oxidative stress were treated to normal HeLa cells, the viability of the HeLa cells was drastically reduced, suggesting increased in vitro lysosomal function (i.e., antimicrobial activity, apoptotic cell death). In addition, we also found that cathepsin B and D were implicated in increased in vitro lysosomal function when isolated from HeLa cells exposed by oxidative stress. Decrease in cathepsin B activity and increase in cathepsin D activity were observed in lysosomes isolated from HeLa cells after treatment with H₂O₂, 6-ODHA, or UVB, but cathepsin B and D were not the sole factors to induce cell death by in vitro lysosomal function. Therefore, these studies suggest a new approach to use lysosomes as antimicrobial agents and as new materials for treating cancer cell lines.

Expansion of adipose tissue‐derived stromal cells at “physiologic” hypoxia attenuates replicative senescence

“…This fact became the rationale for the hypothesis of reduced lysosomal functional activity in senescence, which results in the accumulation of “wrong” proteins and entire cellular structures such as defective mitochondria . At the same time, some experiments demonstrated an elevated LysoTracker fluorescence after different stress conditions and confirmed the increased antimicrobial and apoptotic activity of isolated lysosomes . Thus, the detected increase in the LysoTracker fluorescence may be evidence of enlargement of lysosomal compartment in senescence, which is the cell response on the progressive increase in the number of defective structures.…”

The profile of lysosomal exoglycosidases in replicative and stress-induced senescence in early passage human fibroblasts

“…Lysosomal enzymes are easily release from exposed on oxidative stress lysosomes. It has been shown that oxidative stress causes an increased level of reactive oxygen species and that apoptotic cell death may be induced under severe oxidative stress [17].…”

Sub-lethal oxidative stress induces lysosome biogenesis via a lysosomal membrane permeabilization-cathepsin-caspase 3-transcription factor EB-dependent pathway

“…The proposed mechanisms involved in the activation of autophagy by ROS include inhibition of mTOR activity [12], activation of extracellular regulated kinase (ERK) and/or c-Jun N-terminal kinase [13, 14], nuclear translocation of the high-mobility group box 1 Protein, as shown upon the activation of autophagy by Apogossypolone [15], increase in Beclin 1 expression, and inhibition of the cysteine protease Atg4 activity [16]. However, while these mechanisms mainly focus on the regulation of the formation of autophagic vacuoles, ROS have also been shown to affect lysosomes [17]. Lysosomes and lysosomal proteases play important roles in the final stages of autophagy, such as the fusion of lysosomes with autophagosomes forming autolysosomes followed by proteolytic degradation of the engulfed molecules by lysosomal proteases [19].…”

“…Notably, lysosomal numbers, composition and function are sensitive to various external and internal stresses including redox stress [18]. For example, exposure of HeLa cells to H 2 O 2 , 6-hydroxydopamine (6-OHDA), and UVB irradiation led to an increase in lysosome numbers as well as lysosomal activity [17]. …”