The Type II Pneumocyte
Jacques R. Bourbon in Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
On the other hand, abundant actin-like filaments have been observed in close association with lamellar bodies, especially with those located near the cell surface or in the process of being released.40 Following treatment with cytochalasin D, which alters microfilament organization in many cell types, lamellar bodies were no longer surrounded by actin-like material, and no exocytic lamellar bodies were encountered.40 Conversely, following treatment with isoproterenol, known to stimulate surfactant secretion (see Chapter 7), a greater number of actin-like filaments were associated with lamellar bodies. If cells had been treated with cytochalasin D prior to isoproterenol stimulation, the secretory response to the β-agonist was abolished.145 Actin filaments might therefore be involved in moving lamellar bodies through the cytoplasm and/or in their secretion into alveoli. However, one should note that opposite results were obtained by Rice et al.146 In their hands, following cytochalasin treatment, surfactant secretion was enhanced in a dose-dependent manner.
Quantification of Cellular Elasticity
Malgorzata Lekka in Cellular Analysis by Atomic Force Microscopy, 2017
As an example, the comparison between two cell types will be provided here [51]. Fibroblasts are the cells characterized by highly organized internal structure with well-differentiated both actin and microtubule cytoskeleton (Fig. 4.15a). Actin filaments are dispersed within the entire cell but they are mostly concentrated in the cortex layer beneath the cell membrane. They are organized into two groups: (i) stress fibers visible as a long and thick fibers and (ii) short actin filaments whose presence is barely detected under the fluorescent microscope. Microtubules extend from location close to cell nucleus toward membrane. The length of these cytoskeletal elements can reach even more than 100 microns. The incubation of fibroblasts with 5 μg/ml cytochalasin D leads to depolymerization of actin filaments and, as a consequence, to more homogenous spatial distribution of actin filaments (no stress fibers visible, Fig. 4.15b).
Optical Cardiovascular Imaging
Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer in Cardiovascular Molecular Imaging, 2007
A significant limitation of optical mapping of the heart is motion artifact introduced by muscle contractions. These “movement” artifacts distort optical action potentials by altering the fluorescence intensity. When the tissue contracts, it can move relative to both the sensor and light source, causing artificial changes in fluorescence. Since muscle contraction begins immediately after the action potential upstroke, motion artifacts are most pronounced during the plateau and repolarization phases. Several methods have been used in the past to minimize the effect of motion artifact. Mechanical restriction of the movement can successfully limit the artifact without affecting the physiology of the heart (18). This method works particularly well with small hearts such as mice, rats, and guinea pigs. A popular alternative is the use of various pharmacological agents, such as calcium channel blockers (19), 2,3-butanedione monoxime (BDM) (20,21) or cytochalasin D (22). However, all of these agents may have effects on the electrical activity of the heart. Calcium channel blockers are often avoided due to the many calcium-dependant cellular processes (23,24). BDM has an effect on a variety of ion channels and may alter action potential duration in a number of species (25,26). Therefore, BDM may not be appropriate for studies of repolarization. Cytochalasin D may provide a promising alternative for some species (22,27). Therefore, the effects of any pharmaceutical agents used need to be taken into consideration for an appropriately designed experiment.
TiO2 nanotubes regulate histone acetylation through F-actin to induce the osteogenic differentiation of BMSCs
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Yanchang Liu, Zhicheng Tong, Chen Wang, Runzhi Xia, Huiwu Li, Haoran Yu, Juehua Jing, Wendan Cheng
Considering the known relationship between F-actin and osteoblast differentiation and the specific up-regulation of GCN5 by TiO2 nanotubes, we speculate that F-actin, as a mechanical structure constituting the cytoskeleton, may have a regulatory relationship with GCN5 in BMSCs. In order to further explore the specific regulatory mechanism between F-actin and GCN5 in the process of osteogenic differentiation of BMSCs, we have implemented enhancement/inhibition interventions on F-actin and GCN5 respectively. We used cytochalasin D to inhibit the polymerization of F-actin, and GCN5 was also inhibited. At the same time, the osteogenic differentiation level of BMSCs decreased. When phalloidin was used for intervention, the result was the opposite. But when we silenced GCN5, the F-actin expression level did not change significantly, but the osteogenic differentiation level of BMSCs also began to decrease. Therefore, we have reason to believe that F-actin may act as an upstream to regulate the level of GCN5 in BMSCs and then promote the osteogenic differentiation of BMSCs.
An exploration of aptamer internalization mechanisms and their applications in drug delivery
Published in Expert Opinion on Drug Delivery, 2019
Lin-Yan Wan, Wen-Fang Yuan, Wen-Bing Ai, Yao-Wei Ai, Jiao-Jiao Wang, Liang-Yin Chu, Yan-Qiong Zhang, Jiang-Feng Wu
Caveolar budding is regulated by kinases and phosphatases [26]. Src phosphorylates the caveolae-associated proteins, caveolin 1/2 and dynamin-2. Caveolin is a substrate for Src-family tyrosine kinase, and tyrosine kinase inhibitors (such as tyrphostin A, herbimycid A, PP2 and GEN) can be used to prevent CvME, such as with Gp60-mediated (Gp60 is the receptor for albumin) albumin transcytosis in CvME [71]. CPZ inhibits CME by preventing the recycling of clathrin [72]. The inhibitor cytochalasin D interferes with actin polymerization in macropinocytosis. Wortmannin 83 or 3-methyl adenine (a phosphatidylinositol-3-kinase inhibitor) prevents macropinosome closure. AML and its derivatives, dimethylamiloride and ethylisopropylamiloride, are used to inhibit Na+/H+ exchange proteins in the cell membrane [21]. Consequently, they reduce actin remodeling at the cell membrane by lowering the submembranous pH. AML also blocks internalization through lipid rafts, which inhibits all forms of pinocytosis except for CME [73–77]. GEN inhibits caveolar endocytosis [72,78]. GEN has no effect on the uptake of either transferrin or its aptamer, so the internalization mechanism of the transferrin aptamer does not involve caveolar endocytosis or lipid raft-mediated endocytosis.
Comparison of the effects of multiwall carbon nanotubes on the epithelial cells and macrophages
Published in Nanotoxicology, 2019
Masanori Horie, Yosuke Tabei, Sakiko Sugino, Hiroko Fukui, Ayako Nishioka, Yuji Hagiwara, Kei Sato, Tadashi Yoneda, Atsumi Tada, Tamami Koyama
A549 cells are epithelial cells derived from lung carcinoma. Epithelial cells have phagocytic ability, although it is weaker than that of a phagocyte. TEM observations of the MWCNT-exposed A549 cells showed cellular uptake of the MWCNTs. However, macrophages have stronger phagocytotic abilities than epithelial cells. A phagocytized organic substance, such as a bacterial cell, is digested by hydrolytic enzymes in a phagolysosome. However, nano-objects, including MWCNTs, may not be digestible by a lysosome. Cellular uptake of the MWCNTs was observed using TEM. Induction of IL-8 expression was found in the differentiated, but not undifferentiated, THP-1 cells. Undifferentiated THP-1 cells do not have phagocytic capacity. In addition, inhibition of phagocytosis by cytochalasin D and amiloride inhibited IL-8 expression. Cytochalasin D binds to actin and thus inhibits actin polymerization. As a result, cytochalasin D inhibits phagocytosis by inhibition of membrane ruffling (Yahara et al., 1982; Goddette and Frieden, 1986). Amiloride is sodium-proton exchanger (NHE) inhibitor. Amiloride inhibits cell migration and cellular pH regulation through the inhibition of NHE (Denker and Barber 2002). However, both cytochalasin D and amiloride induce apoptosis (Park et al. 2009). In the present study, the dTHP-1 cells were treated with cytochalasin D and amiloride under low cytotoxic concentrations. When the dTHP-1 cells were treated with 0.2μM cytochalasin D or 100μM amiloride, cellular uptake of the MWCNTs was reduced. However, the cellular uptake could not be inhibited completely. In addition, adhesion of MWCNTs on the cell membrane was not inhibited by cytochalasin D and amiloride. Therefore, IL-8 expression by exposure to MWCNTs would be inhibited partially. Although the MWCNTs adhered onto the surface of the A549 cells, the cellular influence was low. A previous study also reported that exposure to MWCNT at concentration of 100μg/ml did not affect the expression of IL-8 (Pulskamp, Diabaté, and Krug 2007). These results suggest that phagocytosis is an important step for the induction of IL-8 secretion by the MWCNTs. In addition, cytochalasin D reduced the mitochondrial dysfunction caused by exposure to the MWCNTs. Although uptake of the MWCNTs in the A549 cells was hardly observed in the present study, another MWCNT decreased the viability of A549 cells. An inverse relationship between MWCNT uptake and viability was observed (Visalli et al., 2015). The cellular uptake of MWCNTs is also important for the mitochondrial dysfunction caused by MWCNTs.