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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Little is known about melanosome transfer from the melanocyte to neighboring keratinocytes. The melanosomes migrate to the dendritic processes of the melanocyte, which then become pinched off and transferred to the keratinocyte. The area of contact between the keratinocyte and dendritic processes of the melanocyte undulates in vitro. This undulation of the membrane has been attributed to intracellular microfilaments.101 Studies in vitro have demonstrated pigment transfer. When the fungal metabolite cytochalasin B is added to the culture medium, melanocytes shrink, undulations of the keratinocyte membrane cease, and microfilaments disappear. However, the attachment site between melanocytes and keratinocytes remains intact, while desmosomal attachments between keratinocytes split apart. This indicates that the melanocyte-keratinocyte attachment is stable and can withstand the tension, which the keratinocyte-keratinocyte desmosome attachment cannot. Other organelles are not affected by cytochalasin B treatment. The effects of cytochalasin B on microfilaments are reversible 1 h after removal of the drug.90
Internalization of Lipopolysaccharide by Phagocytes
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Richard L. Kitchens, Robert S. Munford
Since large LPS aggregates can bind mCD14, another potential LPS internalization mechanism is phagocytosis. We (30) found that the internalization of [3H]LPS aggregates by THP-1 cells was only slightly (25–35%) inhibited by concentrations of cytochalasin D or cytochalasin H that completely inhibited mCD14-mediated phagocytosis of BODIPY-labeled E. coli. Phagocytosis is thus not required for internalization of LPS aggregates that bind to mCD14. Interestingly, the relatively weak inhibition by cytochalasins also suggests that the mechanism of LPS internalization mediated by GPI-anchored CD 14 differs from that of GPI-anchored CD59, which is internalized by a cytochalasin-inhibitable, non-clathrin-dependent pathway in T lymphocytes (47). Internalization of cross-linked CD59 appears to involve an actin-dependent capping mechanism that does not occur during LPS internalization. On the other hand, the fact that cytochalasins partially inhibit LPS internalization points to some role for the actin cytoskeleton in this process.
Mechanisms of Cholestasis
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
Low-dose administration of cytochalasin also causes cholestasis, which is accompanied by dilatation of canaliculi and a loss of microvilli (Phillips et al., 1975). Cytochalasin has a number of effects, including detachment of microfilaments from the plasma membrane (Oda and Phillips, 1977) and prevention of the polymerization of actin (McLean-Fletcher and Pollard, 1980). Cytochalasin causes a reversible inhibition of canalicular contractions in the isolated hepatocyte couplets (Phillips et al., 1983), inhibits the transport of taurocholate (Reichen et al., 1981; Kacich et al., 1983), and the receptor-mediated transcytosis of IgA (Gebhart, 1984). The exact mechanism by which it inhibits bile flow is not known. As discussed above for phalloidin, disruption of microfilament function may explain the cholestasis.
Length-dependent toxicity of TiO2 nanofibers: mitigation via shortening
Published in Nanotoxicology, 2020
Massimiliano G. Bianchi, Luisa Campagnolo, Manfredi Allegri, Simona Ortelli, Magda Blosi, Martina Chiu, Giuseppe Taurino, Valentina Lacconi, Antonio Pietroiusti, Anna L. Costa, Craig A. Poland, Daniel Baird, Rodger Duffin, Ovidio Bussolati, Enrico Bergamaschi
To investigate the mechanism underlying the higher pro-inflammatory activity of S-TiO2 NF, Raw264.7 cells were exposed for 48 h to the materials (40 μg/cm2) in the presence or in the absence of the cytoskeletal drug cytochalasin B (5 μg/mL), which prevents actin polymerization and, hence, phagocytosis (Figure 6). Both cytochalasin and treatment effects, as well as their interaction, were highly significant on nitrites, TNF-α and IL-6. The stimulation of nitrite production by S-TiO2 NF was almost completely suppressed (Figure 6(A)). The difference in nitrites, TNF-α or IL-6 secretion in cells exposed to L-TiO2 NF or S-TiO2 NF was no more detectable if macrophages were pretreated with cytochalasin, although the drug stimulated TNF-α secretion and inhibited IL-6. Interestingly, cytochalasin B did not reduce significantly either nitrite production or cytokine secretion in macrophages stimulated by LPS. Moreover, L- or S-TiO2 NF did not exert significant toxicity toward macrophages either in the absence (Figure 6(D), Supplementary Figure 1) or in the presence of cytochalasin B (Figure 6(D)) up to 72 h of incubation.
Prospecting in silico antibacterial activity of a peptide from trypsin inhibitor isolated from tamarind seed
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Gerciane Silva de Oliveira, Amanda Maria de Souza Nascimento, Anna Beatriz Santana Luz, Ana Júlia Felipe Camelo Aguiar, Mayara Santa Rosa Lima, Lídia Leonize Rodrigues Matias, Isabel Rodríguez Amado, Thais Souza Passos, Karla Suzane Florentino da Silva Chaves Damasceno, Norberto de Kássio Vieira Monteiro, Susana Margarida Gomes Moreira, Lorenzo Pastrana, Ana Heloneida de Araújo Morais
Cells were grown to 80% confluence, and the medium was replaced by a fresh medium containing TTI (0.3 and 0.6 mg.mL−1), and cells were incubated for 24 h. Then, the medium was aspirated, and the cells were washed with PBS. Subsequently, a fresh medium supplemented with cytochalasin B (Cyt B; Sigma®, St. Louis, MO, USA) was added, and the cells were incubated for another 24 h. Afterward, the cells were washed with PBS, detached using 200 μL of 0.025% Trypsin (0.05% EDTA) for 5 min, and suspended in a culture medium. After centrifuging, the cells were suspended in fixation buffer at 4 °C, consisting of methanol and glacial acetic acid (9: 1 v/v). Washing in fixation buffer was repeated three times.
Toxicological profile of lipid-based nanostructures: are they considered as completely safe nanocarriers?
Published in Critical Reviews in Toxicology, 2020
Asaad Azarnezhad, Hadi Samadian, Mehdi Jaymand, Mahsa Sobhani, Amirhossein Ahmadi
Chromosome damages including, both chromosome loss and chromosome breakage can be simply and sensitively detected in cultured human and/or mammalian cells by using the cytokinesis-block micronucleus assay. If the exposure to a substance results in the chromosomal damages, the chromosome fragments or whole chromosomes that are left behind at anaphase during nuclear division will form Micronuclei (MNi) (Scarfì 2004). DNA damage events are scored specifically in once-divided binucleated cells. In this method, DNA damage events are observed in several forms including, MNi (a biomarker of chromosome breakage and/or whole chromosome loss), nucleoplasmic bridges (NPBs) (a biomarker of DNA misrepair and/or telomere end-fusions), and nuclear buds (NBUDs) (a biomarker of elimination of amplified DNA and/or DNA repair complexes) (Fenech 2007; Thomas and Fenech 2011). This cytogenetic technique was first developed in 1985 to identify the genotoxic effects of materials which has been successfully employed on different cell types to monitor the exposed population. Therefore, the extent of genotoxicity of a substance can be measured by scoring the number of cells containing MNi (Scarfì 2004). Cytochalasin-B which is an inhibitor of microfilament ring assembly required for the completion of cytokinesis, that is used to appearance of once-divided cells (Thomas and Fenech 2011). The term “cytome” refers to the fact that viability status (necrosis, apoptosis), mitotic status (mono-, bi-, and multinucleated), and chromosomal damage or instability status of the cell exposed to the examined materials, consequently this technique refer to cytokinesis block micronucleus cytome (CBMN Cyt) assay.