Chemotherapy in vivo against M109 murine lung carcinoma with cytochalasin B by localized, systemic, and liposomal administration.

Cytochalasin B is a potentially novel microfilament-directed chemotherapeutic agent that prevents actin polymerization, thereby inhibiting cytokinesis. Although cytochalasin B has been extensively studied in vitro, only limited data are available to assess its in vivo potential. Cytochalasin B was administered to Balb/c mice challenged i.d. with M109 murine lung carcinoma to determine whether the agent could affect an established i.d. tumor when the compound is administered s.c. in the region of the i.d. tumor, but not in direct contact with it. Cytochalasin B was also administered either i.p. or s.c. at a distant site or i.v. to determine whether it could affect the long-term development of an established i.d. tumor. Cytochalasin B was then liposome encapsulated to determine whether the maximum tolerated dose (MTD) of the compound could be increased, while reducing immunosuppression that we have previously characterized. Liposomal cytochalasin B was also administered to mice challenged i.d. with M109 lung carcinoma to assess its chemotherapeutic efficacy. The results can be summarized as follows: 1) cytochalasin B substantially delayed the growth of i.d. M109 tumor nodules, inhibited metastatic progression in surrounding tissues, and produced long-term cures in treated mice; 2) liposomal cytochalasin B increased the i.p. MTD by more than 3-fold, produced a different distribution in tissue concentrations, and displayed antitumor effects against M109 lung carcinoma similar to non-encapsulated cytochalasin B. These data show that cytochalasin B exploits unique chemotherapeutic mechanisms and is an effective antineoplastic agent in vivo in pre-clinical models, either in bolus form or after liposome encapsulation.

Nuclear receptor nur77 promotes cerebral cell apoptosis and induces early brain injury after experimental subarachnoid hemorrhage in rats.

Nur77 is a potent proapoptotic member of the nuclear receptor superfamily that is expressed predominantly in brain tissue. It has been demonstrated that Nur77 mediates apoptosis in multiple organs. Nur77-mediated early brain injury (EBI) involves a conformational change in BCL-2 and triggers cytochrome C (cytoC) release resulting in cellular apoptosis. This study investigates whether Nur77 can promote cerebral cell apoptosis after experimentally induced subarachnoid hemorrhage (SAH) in rats. Sprague Dawley rats were randomly assigned to three groups: 1) untreated group, 2) treatment control group, and 3) SAH group. The experimental SAH group was divided into four subgroups, corresponding to 12 hr, 24 hr, 48 hr, and 72 hr after experimentally induced SAH. It remains unclear whether Nur77 can play an important role during EBI after SAH as a proapoptotic protein in cerebral cells. Cytosporone B (Csn-B) was used to demonstrate that Nur77 could be enriched and used to aggravate EBI after SAH. Rats treated with Csn-B were given an intraperitoneal injection (13 mg/kg) 30 min after experimentally induced SAH. We found that Nur77 promotes cerebral cell apoptosis by mediating EBI and triggering a conformational change in BCL-2, resulting in cytoC release. Nur77 activity, along with cerebral cell apoptosis, peaked at 24 hr after SAH onset. After induction of SAH, an injection of Csn-B, an agonist for Nur77, enhanced the expression and function of Nur77. In summary, we have demonstrated the proapoptotic effect of Nur77 within cerebral cells, an effect that can be further exacerbated with Csn-B stimulation.

Actin filament reorganization is a key step in lung inflammation induced by systemic inflammatory response syndrome.

Acute lung injury (ALI) induced by systemic inflammatory response syndrome (SIRS) is characterized by deterioration in pulmonary function and leukocyte-associated lung inflammation. Actin fragment (F-actin) reorganization is required for leukocyte activation, adhesion, and transcription of inflammatory factors. We tested the hypothesis that F-actin plays a central role in SIRS-induced ALI. ALI was produced in a rat model with extracorporeal circulation. Cytochalasin B (CB) pretreatment to block F-actin reorganization improved oxygenation and reduced BAL inflammatory factors and pulmonary neutrophil sequestration, but did not reduce the adhesive molecules of blood leukocytes. We challenged blood neutrophils with TNF-α in vitro to explore the underlying mechanisms. Upon activation, neutrophils became polarized and formed a protrusive leading edge, with an aggregation of CD11b molecules. This effect could be blocked by CB, leading to reduced neutrophil adhesion. In addition, after LPS challenge, we observed F-actin reorganization and the up-regulation of inflammatory factors in pulmonary monocytes, which could also be blocked by CB pretreatment. F-actin reorganization initiates lung inflammation via increased blood neutrophil adhesion and migration, and by the production of inflammatory factors by pulmonary monocytes. Thus, blocking F-actin reorganization may potentially prevent and treat SIRS-induced ALI.

Cytoskeleton disorganization during apoptosis induced by curcumin in A549 lung adenocarcinoma cells.

Several studies have shown that curcumin can induce apoptosis and inhibit growth in human A549 lung adenocarcinoma cells. However, the mechanism is not completely understood yet. In the present study, we investigated the in vitro effect of curcumin on cell viability, apoptosis and disorganization of the actin cytoskeleton in A549 cells. Our results showed that curcumin significantly inhibited the viability of A549 cells in a dose- and time-dependent manner by induced apoptosis. The apoptotic process was associated with a disorganization of the architecture of actin microfilaments and a decrease in the levels of F-actin. DMSO-treated control cells exhibited a well-defined F-actin network that was mainly organized into stress fibers. The actin fibers in cells treated with curcumin or the positive control drug cytochalasin B were disorganized, disassembled, or disrupted, however, the disorganization of actin fibers and apoptosis could be prevented by phalloidin, an F-actin stabilizing compound. Thus, these results demonstrated that actin filament disorganization might play a central role in the curcumin-induced apoptosis of A549 cells.

Vascular remodeling and the local delivery of cytochalasin B after coronary angioplasty in humans.

OBJECTIVES: This study sought to determine the safety, feasibility and outcome of local delivery of cytochalasin B at the site of coronary angioplasty. BACKGROUND: Previous failures in the pharmacologic prevention of restenosis may have been related to inadequate dosing at the angioplasty site as a result of systemic drug administration. Alternatively, although previous experimental protocols have typically targeted control of excess tissue growth (intimal hyperplasia), it now appears that overall arterial constriction (vascular remodeling) is the major contributor to late lumen loss. Cytochalasin B inhibits the polymerization of actin and has proved to be a potent inhibitor of vascular remodeling in animal models. METHODS: In this phase I, multicenter, randomized, controlled trial, cytochalasin B (or matching placebo) was administered to the site of a successful balloon angioplasty using a microporous local delivery infusion balloon. RESULTS: The rate of drug delivery at a constant infusion pressure varied significantly from patient to patient (range 1.7 to 20.2 ml/min), perhaps related to a variable constricting effect of the atherosclerotic plaque on the infusion balloon. The minimal stenosis diameter after the procedure was slightly better in the active drug group (1.86 +/- 0.44 vs. 1.49 +/- 0.63 mm, p < 0.03), but this difference was not seen at four to six weeks. Although the study was not powered for clinical outcomes (n = 43), the combined end point (death, nonfatal infarction or repeat revascularization) was encountered in 20% of the patients receiving cytochalasin B and in 38% of the patients receiving placebo. Clinical restenosis occurred in 18% of the treatment group and 22% of the placebo group. There were no significant differences between groups in biochemical or electrocardiographic variables. CONCLUSIONS: Cytochalasin B can be safely administered by local delivery after successful coronary angioplasty and warrants further study of its efficacy in reducing restenosis.

Electroactivation of rabbit oocytes in an hypotonic pulsing medium and parthenogenetic in vitro development without cytochalasin B-diploidizing pretreatment.

We investigated the electroactivation frequencies, type of activation and in vitro development of rabbit oocytes. In Experiment 1, activation (8 pulses, 12 min apart, 60 microsec, 0.6 kVcm(-1)) was performed by altering osmolarity (190 vs. 320 mOsm kg(-1)) and Ca++ concentration (10, 60 or 100 microM) in mannitol pulsing media. More oocytes were activated in hypotonic pulsing medium, regardless of Ca++ concentration (96 to 100%). Both haploid and diploid parthenogenetic embryos developed to compacted morulae (57 to 92% and 63 to 100%, respectively) regardless of the activation treatment; however, the blastocyst rates were more variable (0 to 74% and 0 to 73%, respectively). In Experiment 2, the effects of pulse duration (30 or 60 microsec) and number of applied pulses (4, 8 or 12) under hypotonic conditions were studied. Activation frequencies were the lowest after four 30 microsec-pulses (58 vs. 88 to 100%, respectively). A lower haploid frequency was obtained when more than four 30 or 60 microsec-pulses were applied (from 67 to 25% and 83 to 0%, respectively). Increasing the number of 60-microsec pulses improved the compacted morula rate of haploid and diploid oocytes (47 to 83% and 57 to 96%, respectively). Overall, haploid development to morulae and blastocysts was lower than diploid development to these stages (69 and 25% vs. 74 and 44%, respectively).

BCG-induced interleukin-6 upregulation and BCG internalization in well and poorly differentiated human bladder cancer cell lines.

Intravesical bacillus Calmette-Guerin (BCG) is a successful therapy for superficial bladder cancer. However, the working mechanism of BCG after intravesical instillation is not completely understood. A functional role of urothelial (tumor) cells in the initiation of the BCG-induced immune reaction should be considered. Here, the possibility of a causal relationship between BCG-induced interleukin-6 (IL-6) synthesis and BCG internalization by urothelial tumor cells was examined in a series of human transitional bladder cancer (TCC) cell lines with different degrees of differentiation. The results showed that the well differentiated TCC cell lines, RT4, SBC-2, and SBC-7, did not possess the capacity to internalize BCG, which was associated with an inability to upregulate IL-6 synthesis when stimulated with BCG. Moreover, these cell lines expressed a low level of constitutive IL-6 synthesis. In contrast, the poorly differentiated TCC cells, T-24, TCC-SUP and J-82, were able to internalize BCG. In T24 and J82, but not in TCC-SUP cells, BCG internalization appeared to result in an upregulation of IL-6 synthesis. Constitutive IL-6 synthesis of the high grade cell lines was found to be cell line-dependent: both TCC-SUP and J82 cells exhibited a high level of constitutive IL-6 synthesis, whereas T24 cells exhibited a low level. The possible relationship between BCG internalization and IL-6 upregulation was studied in detail with the T24 cell line, which exhibited a low constitutive and high BCG-inducible IL-6 synthesis, using anti-BCG antibodies (alphaBCG) and Cytochalasin B as internalization inhibitors. Upregulation of IL-6 synthesis was significantly inhibited by alphaBCG or Cytochalasin B, indicating that internalization is a prerequisite for BCG-induced upregulation of IL-6 synthesis. In conclusion, upregulation of IL-6 production due to BCG internalization by poorly differentiated bladder carcinoma cells may be part of the mode of action of intravesical BCG therapy.

Mouse hepatitis virus type 3 infection provokes a decrease in the number of sinusoidal endothelial cell fenestrae both in vivo and in vitro.

Fenestrations of hepatic endothelial cells play an active role as a sieving barrier allowing extensive exchange between the blood and liver parenchyma. Alteration of these structures may be induced in the course of various pathological events and provoke important perturbations of liver function. We demonstrate here that sinusoidal endothelial cells are permissive for mouse hepatitis virus 3 (MHV3) in vivo and in vitro and that this infection leads to a striking decrease in the number of fenestrae. The disappearance of these structures observed under scanning electron microscopy or in cryofracture preparations in vivo and in vitro cannot be reversed by the action of cytochalasin B on the microfilament network. The decrease in the porosity seems to be related directly to the productive infection of the endothelial cells, because it was not observed in A/J mice resistant to the virus and in susceptible BALB/c mice immunized with a thermosensitive mutant in which no viral replication occurs. In conclusion, a viral infection of liver endothelial cells may cause extensive loss of the fenestrations and thus lead to important functional pertubations.

Functional leukocyte administration in protection against experimental neonatal infection.

Studies have shown that human neonates who develop group B streptococcal sepsis usually lack opsonic antibody (Ab) to their infecting strain and that these neonates may also have impaired polymorphonuclear leukocyte (PMN) function. The present study was designed to determine the efficacy of administration of PMNs or opsonic Ab-containing serum in protecting against group B streptococcal infection in a newborn rat model. After intraperitoneal (IP) injection of congruent to 5 X 10(6) streptococci, animals received separate IP injections of saline, serum lacking opsonic antibody (Ab negative), Ab positive serum or washed adult human PMNs (2 X 10(6)). The mortality rate in 55 neonatal rats infected with group B streptococci who received saline or Ab negative serum was 91%. In contrast, 40 animals who received adult human PMNs at the time of inoculation had a survival rate of 50% (P less than 0.001). Human serum containing opsonic antibody also provided significant protection against mortality in this model (survival rate 51%, P less than 0.001). Leukocytes from normal term neonates, stressed neonates, or ones pretreated with cytochalasin B offered les protection than did functional adult human cell (P less than 0.001).

Effects of dibutyryl cyclic AMP and cytochalasin B on cultured human glioma cells.

Cultured human glioma cells (138 MG) exposed to dibutyryl cyclic AMP (dbc-AMP; 0.1--5 mM) attained an arborized shape with thin processes extending from a rounded cell body. Cytochalasin B (CB; 1--1 muM) induced similar morphological changes. The processes in both dbc-AMP and CB treated cells were formed by retraction of the cell margin. Colchicine (1muM) completely and liver treated phalloidin (0.1 mg/ml) partially inhibited the morphological alterations induced by dbc-AMP and CB. Dbc-AMP was found to arrest cell movement, cell division and uptake of 2-deoxy-D-glucose. CB has the same effects but was more potent. The effects of dbc-AMP and CB could be due to interference with a common cellular structure, e.g. microfilaments.