AIM  To investigate the changes of lysosomal number and distribution, transcription and protein levels of lysosomal associated molecules in vascular smooth muscle cells of carotid artery (CA) in simulated weightless rats by hindlimb unloading tail suspension (HU) for 4 weeks.

  METHODS  4 weeks’ HU rat model was used to simulate the effect of weightlessness on the cardiovascular system. Transmission electron microscopy, western blotting, immunohistochemical staining and quantitative real-time polymerase chain reaction (qRT-PCR) were conducted to examine the number and distribution of lysosomes, the protein level of lysosomal associated membrane protein 1 (LAMP1), lysosomal motor protein kinesin-1, transcription factor EB (TFEB) and E3 (TFE3), and mRNA abundance of TFEB, TFE3 and lysosome related genes in vascular smooth muscle cells of CA.

  RESULTS  Transmission electron microscopy showed that compared to the control (CTR) group, the number of lysosomes of vascular smooth muscle cells of CA was decreased in HU group. Western blot analysis and immunohistochemical staining also indicated that the protein level of LAMP1 of CA were decreased in HU group compared to the CTR (P<0.05), mainly decreased in the media (P<0.05) while that of intima showed no significant difference. In addition, the expression level of kinesin-1 displayed increased(P<0.05). qRT-PCR results showed that compared to the CTR group, the mRNA abundance of lysosomal related genes was increased in CA (P<0.05). Compared to the CTR, the protein levels of TFEB and TFE3 were reduced both in CA of HU rats (P<0.05), while the transcription levels of TFEB and TFE3 were increased in CA (P<0.05).

  CONCLUSION  The number of lysosomes and protein expression level of lysosomal associated molecules of CA vascular smooth muscle cells are reduced in HU group, but the transcription level displays increament, which may contribute to the remodeling of vascular wall.