Nicotine acts on growth plate chondrocytes to delay skeletal growth through the alpha7 neuronal nicotinic acetylcholine receptor.
BACKGROUND
Cigarette smoking adversely affects endochondral ossification during the course of skeletal growth. Among a plethora of cigarette chemicals, nicotine is one of the primary candidate compounds responsible for the cause of smoking-induced delayed skeletal growth. However, the possible mechanism of delayed skeletal growth caused by nicotine remains unclarified. In the last decade, localization of neuronal nicotinic acetylcholine receptor (nAChR), a specific receptor of nicotine, has been widely detected in non-excitable cells. Therefore, we hypothesized that nicotine affect growth plate chondrocytes directly and specifically through nAChR to delay skeletal growth.


RESULTS
We investigated the effect of nicotine on human growth plate chondrocytes, a major component of endochondral ossification. The chondrocytes were derived from extra human fingers. Nicotine inhibited matrix synthesis and hypertrophic differentiation in human growth plate chondrocytes in suspension culture in a concentration-dependent manner. Both human and murine growth plate chondrocytes expressed alpha7 nAChR, which constitutes functional homopentameric receptors. Methyllycaconitine (MLA), a specific antagonist of alpha7 nAChR, reversed the inhibition of matrix synthesis and functional calcium signal by nicotine in human growth plate chondrocytes in vitro. To study the effect of nicotine on growth plate in vivo, ovulation-controlled pregnant alpha7 nAChR +/- mice were given drinking water with or without nicotine during pregnancy, and skeletal growth of their fetuses was observed. Maternal nicotine exposure resulted in delayed skeletal growth of alpha7 nAChR +/+ fetuses but not in alpha7 nAChR -/- fetuses, implying that skeletal growth retardation by nicotine is specifically mediated via fetal alpha7 nAChR.


CONCLUSIONS
These results suggest that nicotine, from cigarette smoking, acts directly on growth plate chondrocytes to decrease matrix synthesis, suppress hypertrophic differentiation via alpha7 nAChR, leading to delayed skeletal growth.
Kawakita
Atsuo
A
Department of Reproductive Biology, National Institute for Child Health and Development, Tokyo, Japan.
Sato
Kazuki
K
Makino
Hatsune
H
Ikegami
Hiroyasu
H
Takayama
Shinichiro
S
Toyama
Yoshiaki
Y
Umezawa
Akihiro
A
D000464:Alginates / Q000378:metabolism; D000818:Animals; D001846:Bone Development / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D005782:Gels; D020723:Glucuronic Acid / Q000378:metabolism; D006132:Growth Plate / Q000166:cytology*; D006603:Hexuronic Acids / Q000378:metabolism; D006801:Humans; D018811:Maternal Exposure; D051379:Mice; D008863:Microspheres; D009154:Mutation / Q000235:genetics; D009538:Nicotine / Q000494:pharmacology*; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012685:Sepharose; D013997:Time Factors; D064569:alpha7 Nicotinic Acetylcholine Receptor
D000464:Alginates; C579167:Chrna7 protein, human; C579166:Chrna7 protein, mouse; D005782:Gels; D006603:Hexuronic Acids; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; D020723:Glucuronic Acid; D012685:Sepharose; D002118:Calcium