Human immunodeficiency virus type 1 Tat protein induces an intracellular calcium increase in human monocytes that requires DHP receptors: involvement in TNF-alpha production

Abstract

HIV-1 Tat protein, acting at the cell membrane, stimulates the production by human monocytes of TNF-alpha, a cytokine implicated in both HIV-1 replication and pathogenesis. Here, we analyze, in primary human monocytes, the mechanisms involved in Tat-stimulated calcium mobilization and its relationship with TNF-alpha production. We show that the Tat protein induces a calcium signal by mobilizing calcium from extracellular stores. This calcium signal is totally blocked when cells are stimulated in the presence of DHP receptor inhibitors such as nimodipine or calcicludine, thus suggesting the implication of this L-type calcium channel. By using RT-PCR amplification, Western blot with antibodies directed against the alpha1D subunit, binding assays with specific agonists or antagonists, and inhibition with specific antisense oligonucleotides, we show that DHP receptors are expressed and functional in primary human monocytes. Interestingly, we demonstrate that Tat-induced calcium mobilization is tightly linked to TNF-alpha production, thus indicating that Tat-induced mobilization and TNF-alpha production are entirely mediated by DHP receptors, as shown by their total inhibition by nimodipine, calcicludine, or anti-alpha1D antisense oligonucleotides.

Oligodendrocytes Are Targets of HIV-1 Tat: NMDA and AMPA Receptor-Mediated Effects on Survival and Development

“…When challenged with 100 nM Tat, [Ca 2ϩ ] i levels rose to ϳ150 nM in day 2 OLs and ϳ230 nM in day 7 OLs, and these increased [Ca 2ϩ ] i levels were maintained during a 20 min experimental period (Fig. 6 B, D-F CaMKII␤ is a molecule central to OL intracellular Ca 2ϩ signaling pathways (Derkach et al, 1999;Bayer and Schulman, 2001;Hudmon and Schulman, 2002) and has been reported to be important in maturation and myelination (Waggener et al, 2013). We investigated whether CaMKII␤ was activated as a consequence of the Tat-induced [Ca 2ϩ ] i increase.…”

“…sence of viral replication, and has been shown to be at high titers in the CSF of cART-controlled patients (Johnson et al, 2013). Multiple cellular abnormalities have been reported in Tat transgenic mice, including reactive astrogliosis and microgliosis (Bruce-Keller et al, 2008), elevated caspase-3 activation in OLs , and synaptodendritic injury (Kim et al, 2003;Fitting et al, 2014), which coincides with deficits in behavior, including learning and memory (Carey et al, 2012;Fitting et al, 2013), and cognitive/motor impairments (Hahn et al, 2015). Most studies suggest Tat-induced inflammation as the predominant cause of CNS injury.…”

“…OL lineage cells express functional ionotropic glutamate receptors (iGluRs), including AMPARs and NMDARs, both in vivo and in vitro (Káradó ttir et al, 2005;Salter and Fern, 2005;Micu et al, 2006;Alix and Fern, 2009). The expression of these receptors on OLs is highly heterogeneous.…”

HIV-1 Tat Protein Induces PD-L1 (B7-H1) Expression on Dendritic Cells through Tumor Necrosis Factor Alpha- and Toll-Like Receptor 4-Mediated Mechanisms

“…Different domains of Tat can interact with specific membrane receptors, including the CD26 receptor (58), the CXCR4 chemokine receptor (46), the L-type calcium channel (59), integrin ␣v␤3 and ␣5␤1 of DCs (60), membrane lipids (55), and the Flk-1/KDR receptor (61). In addition to these potential Tat receptors, we have recently demonstrated that Tat protein is able to recruit the Tolllike receptor 4 (TLR4) pathway, following its interaction with high affinity with TLR4-MD2 complex, to activate the production of proinflammatory tumor necrosis factor alpha (TNF-␣) and antiinflammatory interleukin 10 (IL-10) cytokines (62).…”

Cytokine Reducing Effect of Azelnidipine in Human Peripheral Blood Mononuclear Cells

“…39) However, Xavier et al reported that calcium ions are mobilized from the extracellular environment to enter the cytoplasm through L-type calcium channels and that such mobilization promotes TNF-a production in human PBMCs. 40) A transient rise of [Ca 2ϩ ] i induces persistent activation of NF-kB, 41) which results in the production of TNF-a and MCP-1. An increase of [Ca 2ϩ ] i also causes the activation of Akt, 35) which enhances cytokine production via NF-kB activation, while activated Akt implies the rise of [Ca 2ϩ ] i through the activation of L-type calcium channels.…”