The new anti-actin agent dihydrohalichondramide reveals fenestrae-forming centers in hepatic endothelial cells.
BACKGROUND
Liver sinusoidal endothelial cells (LSECs) react to different anti-actin agents by increasing their number of fenestrae. A new structure related to fenestrae formation could be observed when LSECs were treated with misakinolide. In this study, we investigated the effects of two new actin-binding agents on fenestrae dynamics. High-resolution microscopy, including immunocytochemistry and a combination of fluorescence- and scanning electron microscopy was applied.


RESULTS
Halichondramide and dihydrohalichondramide disrupt microfilaments within 10 minutes and double the number of fenestrae in 30 minutes. Dihydrohalichondramide induces fenestrae-forming centers, whereas halichondramide only revealed fenestrae-forming centers without attached rows of fenestrae with increasing diameter. Correlative microscopy showed the absence of actin filaments (F-actin) in sieve plates and fenestrae-forming centers. Comparable experiments on umbilical vein endothelial cells and bone marrow sinusoidal endothelial cells revealed cell contraction without the appearance of fenestrae or fenestrae-forming centers.


CONCLUSIONS
(I) A comparison of all anti-actin agents tested so far, revealed that the only activity that misakinolide and dihydrohalichondramide have in common is their barbed end capping activity; (II) this activity seems to slow down the process of fenestrae formation to such extent that it becomes possible to resolve fenestrae-forming centers; (III) fenestrae formation resulting from microfilament disruption is probably unique to LSECs.
Braet
Filip
F
Laboratory for Cell Biology and Histology, Free University of Brussels (VUB), Laarbeeklaan 103, 1090 Brussels-Jette, Belgium. filipbra@cyto.vub.ac.be
Spector
Ilan
I
Shochet
Nava
N
Crews
Phillip
P
Higa
Tatsuo
T
Menu
Eline
E
de Zanger
Ronald
R
Wisse
Eddie
E
D000199:Actins / Q000037:antagonists & inhibitors*; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000166:cytology* / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D008099:Liver / Q000166:cytology* / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D008387:Marine Toxins / Q000494:pharmacology; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000199:Actins; D006576:Heterocyclic Compounds, 4 or More Rings; D018942:Macrolides; D008387:Marine Toxins; C470371:dihydrohalichondramide; C470372:halichondramide