HIV Proteins Regulate Bone Marker Secretion and Transcription Factor Activity in Cultured Human Osteoblasts with Consequent Potential Implications for Osteoblast Function and Development

Abstract

A high incidence of decreased bone mineral density (BMD) has increasingly been associated with HIV infection. In this study mesenchymal stem cell (MSC) and human osteoblast (hOB) cell lines were treated with HIV tat, HIV rev, HIV p55-gag, HIV gp120 and HTLV env (100 ng/ml, 24 h). Cells were then analyzed for calcium deposition, alkaline phosphatase (ALP) activity, and lipid levels using established methods. Real-time PCR with gene-specific primers was used to quantify the mRNA levels of the transcription factors RUNX-2 and PPARgamma, transcription factors known to be pro-osteogenic and pro-adipogenic, respectively. The levels of secreted bone markers and transcription factor activity were determined using commercial assays. In OBs, HIV p55-gag and gp120 were seen to reduce calcium deposition, ALP activity, levels of secreted BMP-2, -7, and RANK-L, and the expression and activity of RUNX-2. The levels of osteocalcin were also significantly reduced by p55-gag treatment, while gp120 also increased PPARgamma activity. Lipid levels were also increased by gp120 treatment. The ability of MSCs to develop into functioning OBs was also affected by the presence of HIV proteins, with p55-gag inducing a decrease in osteogenesis, while rev induced an increase. HIV proteins can potentially modulate OB development and function in vitro via modulation of bone maker secretion and RUNX-2 and PPARgamma transcription factor activity.

A study of bone mineral density among people living with HIV in India and its correlation with CD4 count

“…In untreated HIV, through direct viral effects and inflammatory effects, bone resorption and bone formation are uncoupled. 10 In vitro studies have shown that HIV viral proteins Vpr and gp120 stimulate osteoclast activity and p55-gag suppresses osteoblast activity and increases osteoblast apoptosis. [11][12][13] In addition, inflammatory cytokines, such as tumour necrosis factor α and interleukin 6 promote osteoclastogenesis and bone resorption.…”

“…10 In vitro studies have shown that HIV viral proteins Vpr and gp120 stimulate osteoclast activity and p55-gag suppresses osteoblast activity and increases osteoblast apoptosis. [11][12][13] In addition, inflammatory cytokines, such as tumour necrosis factor α and interleukin 6 promote osteoclastogenesis and bone resorption. [14][15][16] High concentrations of HIV RNA have been associated with elevated levels of receptor activator of nuclear factor κ β ligand (RANKL), an osteoblast secreted cytokine that promotes osteoclast formation.…”

Cobalt ions induce chemokine secretion in primary human osteoblasts

“…[39][40][41] Briefly, treated and control cells were fixed in 70% ice-cold ethanol for 1 h. The cells were then stained with 40 mM alizarin red (Sigma), pH 4.2, for 10 min with gentle agitation and rinsed five times with double distilled water. Alizarin Red S was extracted from fixed cells by 500 mL 10% cetylpyridinum chloride (CPC) treatment for 20 min.…”

Avaliação cefalométrica da morfologia craniofacial em crianças e adolescentes HIV positivos

“…A infecção pelo HIV por si e/ou associada a estados de ativação imune e inflamatória, pode alterar a osteoclastogênese, aumentando a taxa de apoptose de osteoblastos primários, reduzindo a deposição de cálcio e a atividade da fosfatase alcalina, diminuindo proteínas específicas de osso e comprometendo a diferenciação de células mesenquimais em osteoblastos (O'Brien et al, 2001;Fakruddin;Laurence, 2003;Cotter et al, 2007;Gibellini et al, 2008;Gutierrez;Masiá, 2011).…”