Effects of sodium salicylate on the expression of HSP27 protein during oxidative stress in tissue-cultured human lens epithelial cells

The protective role of HSP27 in ocular diseases

Heat shock proteins (HSPs) are stress-induced proteins that are important constituents of the cell's defense system. The activity of HSPs enhances when the cell undergoes undesirable environmental conditions like stress. The protective roles of HSPs are due to their molecular chaperone and anti-apoptotic functions. HSPs have a central role in the eye, and their malfunction has been associated with the manifestation of ocular diseases. Heat shock protein 27 (HSP27, HSPB1) is present in various ocular tissues, and it has been found to protect the eye from disease states such as retinoblastoma, uveal melanoma, glaucoma, and cataract. But some recent studies have shown the destructive role of HSP27 on retinal ganglionic cells. Thus, this article summarizes the role of heat shock protein 27 in eye and ocular diseases and will focus on the expression, regulation, and function of HSP27 in ocular complications.

Oxidative stress as a significant factor for development of an adaptive response in irradiated and nonirradiated human lymphocytes after inducing the bystander effect by low-dose X-radiation

X-radiation (10cGy) was shown to induce in human lymphocytes transposition of homologous chromosomes loci from the membrane towards the centre of the nucleus and activation of the chromosomal nucleolus-forming regions (NFRs). These effects are transmitted by means of extracellular DNA (ecDNA) fragments to nonirradiated cells (the so-called bystander effect, BE). We demonstrated that in the development of the BE an important role is played by oxidative stress (which is brought about by low radiation doses and ecDNA fragments of the culture medium of the irradiated cells), by an enzyme of apoptosis called caspase-3, and by DNA-binding receptors of the bystander cells, presumably TLR9. Proposed herein is a scheme of the development of an adaptive response and the BE on exposure to radiation. Ionizing radiation induces apoptosis of the radiosensitive fraction of cells due to the development of the "primary" oxidative stress (OS). DNA fragments of apoptotic cells are released into the intercellular space and interact with the DNA-binding receptors of the bystander cells. This interaction activates in lymphocytes signalling pathways associated with synthesis of the reactive oxygen species and nitrogen species, i.e., induces secondary oxidative stress accompanied by apoptosis of part of the cells, etc. Hence, single exposure to radiation may be followed by relatively long-lasting in the cellular population oxidative stress contributing to the development of an adaptive response. We thus believe that ecDNA of irradiated apoptotic lymphocytes is a significant factor of stress-signalling.

Effects of mitogen-activated protein kinase signal pathway on heat shock protein 27 expression in human lens epithelial cells exposed to sodium salicylate in vitro

The roles of mitogen-activated protein kinase (MAPK) signal pathway in sodium salicylate-induced expression of heat shock protein 27 (HSP27) in human lens epithelial cells (HLECs-B3) in vitro were investigated. HLECs-B3 were incubated in the fresh media containing sodium salicylate at different concentrations for different durations, and allowed to be recovered in fresh medium without sodium salicylate for different durations with or without pretreatment with p38MAPK inhibitor (SB203580), ERK1/2 inhibitor (PD98059) and JNK/SAPK inhibitor (SP600125). The expression of P38MAPK, ERK1/2, JNK/SAPK, phosphorylated P38MAPK, phosphorylated ERK1/2, phosphorylated JNK/SAPK and HSP27 was detected by Western blot. The expression of HSP27 mRNA and protein was detected by RT-PCR and immunohistochemistry respectively. It was found there was only weak expression of HSP27 in normal HLECs. The expression of HSP27 was not detectable in HLECs-B3 that were exposed to sodium salicylate (55 mmol/L) for 1-5 h. It was indicated that recovery from sodium salicylate (>35 mmol/L) significantly increased the synthesis of HSP27. The expression of HSP27 was up-regulated in HLECs-B3 under sodium salicylate recovery for 3 h, reached the peak level for 6 h, and returned to the level of control cells by 24 h. Activation of P38MAPK from sodium salicylate stimulation occurred at 30th min, and increased significantly at 1st h, then declined and returned to baseline level at 3rd h under sodium salicylate recovery. Activation of ERK1/2 occurred at 1st h and reached the peak level at 6th h under sodium salicylate recovery. However, JNK/SAPK was inactivated by sodium salicylate. The expression of HSP27 could be down-regulated with the pretreatment of SB203580 and PD98059 jointly. It is concluded that sodium salicylate can induce the expression of HSP27 in HLECs-B3. The effects are mediated, at least in part, through the activation of P38MAPK and ERK1/2 signaling pathway.