1.Apoptotic death of beta cells after optic nerve transection in adult cats.
Kurimoto T1, Miyoshi T, Suzuki A, Yakura T, Watanabe M, Mimura O, Fukuda Y. J Neurosci. 2003 May 15;23(10):4023-8.
We have revealed previously that the survival rate of beta cells of cat retinal ganglion cells (RGCs) rapidly decreased to 29% on day 7 after optic nerve transection, whereas that of alpha cells slowly decreased to 64% on day 14 (Watanabe et al., 2001). The reason that beta cells die more rapidly than alpha cells was not clear. In the present study, we tested the possibility that the rapid death of beta cells is attributable to apoptosis, as shown for some axotomized RGCs in rats. The following results were obtained. First, the proportion of pyknotic cells in Nissl-stained cat retinas started to increase sharply starting on day 4 and reached a peak on day 6 after optic nerve transection. The time course of occurrence of pyknotic cells corresponded well with that of the rapid death of axotomized beta cells. Secondly, the proportion of pyknotic cells was the highest in the area centralis (AC), in which beta cells are densely distributed. The preferential death of axotomized RGCs in the AC was also confirmed by terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling staining in cross sections.
2.Contribution of calpain to cellular damage in human retinal pigment epithelial cells cultured with zinc chelator.
Tamada Y1, Walkup RD, Shearer TR, Azuma M. Curr Eye Res. 2007 Jun;32(6):565-73.
PURPOSE: We previously showed involvement of calpains in neural retina degeneration induced by hypoxia and ischemia-reperfusion. Age-related macular degeneration (AMD) is one of the leading causes for loss of vision. AMD showed degeneration of neural retina due to dysfunction and degeneration of the retinal pigment epithelium (RPE). RPE performs critical functions in neural retina, such as phagocytosis of shed rod outer segments. The purpose of the current study was to determine the contribution of calpain-induced proteolysis to damage in cultured human RPE cells. Zinc chelator TPEN was used to induce cellular damage as zinc deficiency is a suspected risk factor for AMD.
3.Chitosan induces apoptosis via caspase-3 activation in bladder tumor cells.
Hasegawa M1, Yagi K, Iwakawa S, Hirai M. Jpn J Cancer Res. 2001 Apr;92(4):459-66.
Recently, because of its low toxicity and biological effects, chitosan has been widely used in the medical and pharmaceutical fields, e.g., for nasal or oral delivery of peptide or polar drug delivery. Here, we report a growth-inhibitory effect of chitosan on tumor cells. The growth inhibition was examined by WST-1 colorimetric assay and cell counting. We also observed DNA fragmentation, which is characteristic of apoptosis, and elevated caspase-3-like activity in chitosan-treated cancer cells. The findings suggest that chitosan may have potential value in cancer therapy.
4.Degradation of focal adhesion proteins paxillin and p130cas by caspases or calpains in apoptotic rat-1 and L929 cells.
Shim SR1, Kook S, Kim JI, Song WK. Biochem Biophys Res Commun. 2001 Aug 24;286(3):601-8.
Immunofluorescence microscopy revealed the rearrangement and gradual dissociation of paxillin from focal adhesion sites during apoptosis. In vitro, cleavage of paxillin by caspase-3 generated a 42-kDa fragment, among other products, while cleavage by calpain generated a different set of fragments. In Rat-1 cells, cleavage of paxillin by caspase-3 was suppressed by zVAD-fmk or zDEVD-cmk, making caspase-3 a likely executioner during etoposide-induced apoptosis. In contrast, the cleavage of paxillin and p130cas in apoptotic L929 cells was blocked by calpain-specific inhibitors, which also reduced the death rate by 23 to 44%. Therefore, The disassembly and degradation of p130cas and paxillin during apoptosis may controlled by both caspases and calpains, depending upon their cellular contexts. Our findings also suggest that focal adhesion proteins paxillin and p130cas take part in integrin-mediated signaling for cell survival, and that their cleavage by caspase and/or calpain may not only disrupt focal adhesion complexes, but may also impede cell survival signaling.