Ultraviolet A radiation transiently disrupts gap junctional communication in human keratinocytes

2003 ◽  
Vol 284 (1) ◽  
pp. C51-C59 ◽  
Author(s):  
Nicolas Provost ◽  
Marielle Moreau ◽  
Armelle Leturque ◽  
Carine Nizard
Keyword(s):  
Actin Cytoskeleton ◽  
Human Keratinocytes ◽  
Ultraviolet A ◽  
Gap Junctional Communication ◽  
Uva Irradiation ◽  
Junctional Communication ◽  
Normal Human Keratinocytes ◽  
Normal Human ◽  
Gap Junctional ◽  
Dose Dependent

Ultraviolet A (UVA) (320–400 nm) radiation is known to cause cutaneous aging and skin cancer. We studied the effect of UVA (365 nm) radiation on the human epidermis by focusing on keratinocyte gap junction-mediated intercellular communication (GJIC). We observed a dose-dependent 10-fold decrease in GJIC induced by UVA in normal human keratinocytes. This decrease in GJIC was associated with time-dependent internalization of connexin43 (Cx43). UVA radiation also damaged the actin cytoskeleton, as shown by microfilament disappearance. Importantly, the decrease in GJIC was transient when keratinocytes were irradiated with 10 J/cm2UVA, with a return to baseline values after 8 h. Concomitantly, Cx43 was relocalized and the actin cytoskeleton was restored. UVA irradiation and 12- O-tetradecanoylphorbol 13-acetate (TPA) treatment activated protein kinase C and reduced GJIC. However, Cx43 localization and phosphorylation were differently regulated by the two treatments. This suggests that at least two different pathways may mediate the observed fall in GJIC. These findings identify keratinocyte GJIC as a new UVA target that might sensitize human skin to photoaging and cancer formation.

Enhancement of Differentiation and Homeostasis of Human Osteoblasts by Interaction with Hydroxyapatite in Microsphere Form

2006 ◽  
Vol 309-311 ◽  
pp. 1293-1298 ◽  
Author(s):  
Ryusuke Nakaoka ◽  
Toshie Tsuchiya
Keyword(s):  
Wear Debris ◽  
Periprosthetic Bone ◽  
Artificial Joints ◽  
Human Osteoblasts ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Enhanced Expression ◽  
Normal Human ◽  
Good Biocompatibility ◽  
Gap Junctional

The aseptic loosening of artificial joints with associated periprosthetic bone resorption may be partly due to the suppression of osteoblast function to form new bone by wear debris derived from the joint. To assess the effect of wear debris on osteoblasts, we cultured normal human osteoblasts (NHOst) in contact with several kinds of microspheres as models of wear debris. The NHOst in contact with polystyrene, polyethylene, and alumina microspheres showed a lower differentiation level than NHOst alone as estimated from the amounts of deposited calcium. On the other hand, hydroxyapatite particles enhanced the differentiation of NHOst. In addition, sintered hydroxyapatite enhanced expression of osteocalcin mRNA and gap junctional communication of NHOst. This study suggests that polystyrene, polyethylene, and alumina microspheres have the potential to disorder not only the differentiation but also the homeostasis of NHOst in contact with them. However, hydroxyapatite enhanced the differentiation as well as the homeostasis of NHOst, even in microsphere form, suggesting its good biocompatibility as biomaterials for bone tissues.

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