Genetic Modulation of Initial Sensitivity to Δ9-Tetrahydrocannabinol (THC) Among the BXD Family of Mice.

Cannabinoid receptor 1 activation by the major psychoactive component in cannabis, Δ9-tetrahydrocannabinol (THC), produces motor impairments, hypothermia, and analgesia upon acute exposure. In previous work, we demonstrated significant sex and strain differences in acute responses to THC following administration of a single dose (10 mg/kg, i.p.) in C57BL/6J (B6) and DBA/2J (D2) inbred mice. To determine the extent to which these differences are heritable, we quantified acute responses to a single dose of THC (10 mg/kg, i.p.) in males and females from 20 members of the BXD family of inbred strains derived by crossing and inbreeding B6 and D2 mice. Acute THC responses (initial sensitivity) were quantified as changes from baseline for: 1. spontaneous activity in the open field (mobility), 2. body temperature (hypothermia), and 3. tail withdrawal latency to a thermal stimulus (antinociception). Initial sensitivity to the immobilizing, hypothermic, and antinociceptive effects of THC varied substantially across the BXD family. Heritability was highest for mobility and hypothermia traits, indicating that segregating genetic variants modulate initial sensitivity to THC. We identified genomic loci and candidate genes, including Ndufs2, Scp2, Rps6kb1 or P70S6K, Pde4d, and Pten, that may control variation in THC initial sensitivity. We also detected strong correlations between initial responses to THC and legacy phenotypes related to intake or response to other drugs of abuse (cocaine, ethanol, and morphine). Our study demonstrates the feasibility of mapping genes and variants modulating THC responses in the BXDs to systematically define biological processes and liabilities associated with drug use and abuse.

Endothelial Bmp4 is induced during arterial remodeling: effects on smooth muscle cell migration and proliferation.

BACKGROUND: Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta superfamily of proteins that have multiple functional roles in mammalian development. A role for BMP4 in adult vascular remodeling has recently been suggested. We evaluated the expression of Bmp4 during neointimal lesion development in vivo. MATERIALS AND METHODS: Heterozygous Bmp4(lacZ/+) mice were used to evaluate in vivo Bmp4 expression after carotid ligation. beta-galactosidase (beta-gal) activity was evaluated in histological sections 1 to 14 d after carotid ligation and this was compared with control carotid arteries. The effects of recombinant human (rh) BMP4 on smooth muscle cell (SMC) migration and proliferation were evaluated using a rat aortic SMC line. We next assessed the effects of BMP4 signaling by over-expressing a constitutively active BMP receptor (BMPR-IA/Alk-3) using adenovirus-mediated gene transfer. SMC proliferation, migration, and apoptosis were evaluated in adenovirus transfected cells. RESULTS: Ligated carotid arteries expressed endothelium-specific beta-gal staining after 1 d. Staining intensity increased at both 3 d and 1 wk after ligation and remained stable at 2 weeks while no beta-gal staining was observed in control vessels. Endothelial-specific expression of beta-galactosidase was confirmed through positive staining for PECAM-1. When human recombinant BMP4 was added to cultured SMCs, it inhibited migration but did not affect cultured SMC proliferation. SMCs infected with adenovirus encoding for the active BMP receptor Alk-3 demonstrated dose-dependent receptor expression. Alk-3 over-expressing cells showed a dose-dependent decrease in proliferation and migration but no effect on apoptosis. CONCLUSIONS: These results demonstrate that endothelial Bmp4 expression is upregulated after carotid ligation in vivo, and furthermore, that activating the BMP signaling cascade results in decreased SMC proliferation and migration. This suggests that BMPs may counterbalance the effect of mitogen up-regulation observed during the development of neointimal hyperplasia.