Table 2.

Cellular and molecular interactions (in vitro)

Major effects	HIV pathogena	ARV	Opioids	Outcome	Model system (in vitro)	Citation(s)
Mixed-Glia
HIV expression	HIV	No	• Dynorphin • U50,488 (KOR agonists)	• ↑ HIV-1 expression, • Dynorphin (KOR agonist) ↑ TNF-α, IL-6 mRNA and protein	Human fetal neural cells, HIV-infected promonocyte (U1) line	(Chao et al. 1995)
	HIVSF162	No	• U50,488 • U69,593 • Dynorphin1–17; (KOR agonists) • Morphine	• KOR agonists ± TNF-α differentially ↓ HIV p24	Human, primary mixed neurons and glia	(Chao et al. 1998a)
Chemokines	Tat1–86	No	Morphine	• ↑ CCL5, CCL2 • ↑ [Ca2+]i (Beclin1 dependent) • ↓ Autophagy	Mouse, primary mixed glia	(Lapierre et al. 2018)
	HIVSF162 (R5)	No	Morphine	• ↑ HIV-1 Tat-induced LTR expression • ↑ CCR5 expression (inhibited by bivalent ligand in astrocytes) • ↑ IL-6 • ↑ CCL5	Human, primary mixed glia	(El-Hage et al. 2013)
Glial restricted precursors: survival & MOR, DOR, KOR expression	Tat1–72	No	Morphine (acting via DOR and/or KOR)	• ↑ Caspase-3 activation & ↑ cell death by Tat or morphine via DOR, KOR • No opioid-Tat interactions	Mouse, primary glial precursors	(Buch et al. 2007)
MOR expression in NPCs; NPC survival and developmental fate	Tat1–72	No	Morphine	• MOR expressed by subsets of NPCs • ↑ Astrocyte and immature glial death	Mouse, primary mixed glia	(Khurdayan et al. 2004)
MOR and CCR5 interactions	Tat1–86 (from HIVIIIB)	No	Morphine	• ↓ Neuronal survival via CCR5 activation in glia (rescued by BDNF treatment)	Mouse, primary neurons and glia	(Kim et al. 2018)
HIV infectivity MOR-CCR5 dimerization	HIVSF162 (R5)	No	Morphine CCR5-MOR bivalent ligand 1b	• MOR-CCR5 bivalent ligand blocks HIV infection in astroglia, but not microglia, with morphine • MOR-CCR5 bivalent ligand blocks the fusion of HIV gp160 and CCR5-CD4-expressing HEK cells	Human, primary astrocytes and microglia; HEK-293T cells	(Yuan et al. 2013; Arnatt et al. 2016)
HIV expression and maturational fate of neurons and astroglia	HIVBaL (R5)	No	Morphine	• ↑ HIV p24 and ↑ Tat mRNA levels with morphine after 21 days • ↓ Proliferation of neural progenitors; ↑ astroglial and ↑ neuronal differentiation	Human, neural progenitors	(Balinang et al. 2017)
Astrocytes
HIV expression	HIVSF162 (R5)	No	Morphine	• ↑ HIV p24 • ↑ CCL2	Human, primary astrocytes	(Rodriguez et al. 2017)
Toll-like receptor (TLR) expression/function	• Tat1–72 • gp120	No	Morphine	• ↑ TLR2 with Tat, Tat + morphine, gp120 • ↓ TLR9 with Tat, morphine, gp120	Mouse, primary astrocytes	(El-Hage et al. 2011a)
Chemokines	Tat1–72	No	Morphine	• ↑ CCL5, CCL2 • ↑ IL-6 • ↑ [Ca2+]i	Mouse, primary astrocytes	(El-Hage et al. 2005)
	Tat1–72	No	Morphine	• ↑ CCL2 • ↑ CCL5 • ↑ Microglial migration	Mouse, primary astrocytes	(El-Hage et al. 2006a)
	Tat1–72	No	Morphine	• ↑ CCL2, ↑ IL-6, ↑ TNF-α • ↑ [Ca2+]i • ↑ NF-κB trafficking and transcription • No interaction / acceleration with morphine	Mouse, primary astrocytes	(El-Hage et al. 2008b)
	Tat	No	• U50,488 (KOR agonist) • Nor-BNI (KOR antagonist)	• U50,488 ↓ CCL2 • U50,488 ↓ NF-κB	Human, primary astrocytes	(Sheng et al. 2003)
	N/A	No	Morphine	• ↑ CCR5, CCR3, CXCR2 • ↓ IL-8, CCL4	Human, astrocytoma U87 cell line, primary astrocytes	(Mahajan et al. 2002)
	• Tat1–86 • gp120IIIB	No	Morphine	Regional differences in cytokine and ROS production —differed for each insult	Mouse, primary astrocytes	(Fitting et al. 2010a)
Oxidative stress / damage	Tat1–72	No	• DPDPE • SNC-80 (DOR agonists)	DOR agonists ↓ Tat-induced oxidative stress	Human derived brain cell line (SK-N-SH)	(Wallace et al. 2006)
Inflammation, maturation /plasticity	• Tat86 • Tat101	No	Morphine	↓ β-catenin signaling and variably decreases TrkB, BDNF, and NLRP1 mRNA in fetal astrocytes b	Human, U87MG and fetal astrocytes	(Chen et al. 2020)
Microglia
HIV replication	HIVSF162 (R5)	No	• Endomorphin-1 • Endomorphin-2 (MOR agonists)	• ↑ HIV p24 with endomorphin-1, but not endomorphin-2 • Endomorphin-1 acts via MOR, but not DOR / KOR	Human, primary microglia	(Peterson et al. 1999)
	HIVSF162 (R5)	No	Morphine	↑ HIV p24	Human, primary microglia	(El-Hage et al. 2014)
	HIVSF162 (R5)	No	• U50,488; U69,593 (KOR agonists) • Dynorphin Al-13	↓ HIV p24	Human, primary microglia	(Chao et al. 1996b)
	• HIVJR-FL (R5) • gp120	No	β-endorphin	• ↑ HIV expression • ↑ HIV p24 (14-day post infection) • gp120 ↑ IL-1, TNF, IL-6	Human, fetal microglia	(Sundar et al. 1995)
	HIVSF162	No	• 8-CAC, U50,488 (KOR agonists) • Cocaine	• KOR agonist ↓ p24; blocked by KOR antagonists • KOR agonist negates cocaine-induced ↑ HIV	Human, fetal brain microglia	(Gekker et al. 2004)
	HIVSF162	No	OPRL1 antisense Nociceptin / orphanin FQ (OPRL1 agonist)	• OPRL1 antisense (and sense) ↓ p24 • Nociceptin, no effect on p24	Human, fetal brain microglia and mixed neurons/glia	(Chao et al. 1998b)
HIV expression	• HIVSF162 • Tat	ZDV	U50,488 (KOR agonist)	• ↓ p24 on day 14 with U50,488 • ↓ Neurotoxicity (U50,488) • ↓ Quinolinate by microglia	Human, fetal microglia and neural cells	(Chao et al. 2000)
Chemokines and Cytokines	Tat1–72	No	Morphine	• ↑ CCR5 • ↑ CD11b, ↑ CD40 • ↑ TNF-α, ↑ IL-6, ↑ IP-10 • ↑ iNOS	Mouse, BV-2 and primary microglia	(Bokhari et al. 2009)
MOR signaling	Tat1–72	No	Morphine	• ↑ MOR (intracellular) • ↑ MOR mRNA	Mouse, N9 and primary microglia	(Turchan-Cholewo et al. 2008)
Oxidative Stress	Tat1–72	No	Morphine	• ↑ ROS [O2− (DHE), ↑ HO2•, H2O2 (DCF)] • ↑ Protein carbonyls	Mouse, N9 and primary microglia	(Turchan-Cholewo et al. 2009)
Glutamate release	Tat1–72	No	Morphine	↑ Glutamate release via ↑ xc− cystine-glutamate antiporter expression/function	Mouse, primary microglia	(Gupta et al. 2010)
Neurons
HIV expression	HIV	No	Morphine	↑ HIV expression	Human derived, SH-SY5Y neuroblastoma cells	(Squinto et al. 1990)
Homeostasis and Injury	Tat1–86	No	Morphine	• ↑ [Ca2+]i, • ↑ [Na+]i • ↓ ΔΨm (mitochondrial) instability • ↑ Dendritic degeneration	Mouse, primary neurons	(Fitting et al. 2014a)
Mitochondrial inner membrane potential and ROS	• Tat1–86, Tat1–72 • gp120	No	Morphine	↑ ΔΨm instability and oxidative stress ↑ with Tat + morphine, ↑ neuroprotection with allopregnanolone	Human, primary neurons ; mouse, striatal medium spiny neurons; mouse, striatal medium spiny neurons, SH-SY5Y neuroblastoma cells	(Turchan-Cholewo et al. 2006; Paris et al. 2020)
Neuronal survival	Tat1–86	No	Morphine	• ↓ Neuronal survival from Tat + morphine and ↓ glial CX3CL1 rescued by CX3CL • CX3CL1 (fractalkine) regulates microglial motility	Mouse, primary neurons and mixed glia	(Suzuki et al. 2011)
	Tat1–86	No	Morphine	• ↓ Proliferation • ↑ ERK1/2 activation • ↑ p53 and p21 • ↓ Cyclin D1 and Akt levels	Human, neuronal precursors	(Malik et al. 2014)
	Tat1–72, Tat1–86	No	Morphine	• ↓ Neuronal survival • ↑ Neuronal survival with ibudilast (AV411) (inhibiting glial NF-κB blocks Tat ± morphine neurotoxicity)	Mouse, primary neurons and mixed glia	(Gurwell et al. 2001; El-Hage et al. 2014)
White matter/oligodendroglial pathology
Changes in OL survival and morphology	Tat1–86	No	Morphine (25 mg pellet, 7 days); morphine (in vitro)	• ↑ Degeneration of OLs • ↑ TUNEL reactivity • ↑ Caspase-3 activation	Mouse, Tat tg; primary OLs	(Hauser et al. 2009)
Blood-brain barrier and the neurovascular unit
BBB model integrity and function	Tat1–86	No	Morphine	• ↑ TNF-α • ↑ IL-8 • ↓TEER • ↑ JAM-2 expression • ↑ Monocyte transmigration with CCL5	Human, using primary BMVEC and primary astrocytes	(Mahajan et al. 2008)
ARV accumulation	Tat1–86	DTG FTC TFV	Morphine	• ↓ Intracellular ARV concentrations	Human, primary astrocytes	(Patel et al. 2019)
HIV-1 strain differences
Neuronal Survival	Tat1–86 (clades B & C)	No	Morphine	• ↓ Neuronal survival via MOR on mixed glia • ↑ ROS in astrocytes • ↑ Iba1 and 3-NT microglia with morphine	Mouse, primary neurons and mixed glia	(Zou et al. 2011)
	• gp120IIIB • gp120MN (X4) • gp120ADA (R5)	No	Morphine	↓ Neuronal survival in presence of glia with gp120MN and transiently with gp120IIIB (X4), not R5-tropic gp120, in combination with morphine	Mouse, primary neurons and mixed glia	(Podhaizer et al. 2012)
Proliferation and maturational fate of neural progenitors and oligodendroglia	• HIVSF162 (R5) • HIVIIIB (X4)	No	Morphine	• ↓ Proliferation of immature neural and OL progenitors with Tat + morphine • ↓ NPC DNA synthesis with R5-tropic HIV + morphine • ↑ NPC DNA synthesis with X4-tropic HIV + morphine	Mouse, Tat tg; Mouse, Human, primary neural progenitors	(Hahn et al. 2012)
GABA function	• HIVBaL (R5) • gp120 (ADA, MN, and IIIB) • Tat1–86	No	Morphine	• Tat or morphine ↓ KCC2 levels via CCR5 • ↑ KCC2 prevents Tat and R5 HIV, gp120, but not X4, gp120 neurotoxicity ± morphine	Human, primary neurons, hNPCs	(Barbour et al. 2020)
Astroglial CCL5 and neuroprotection	• gp120IIIB (X4) • gp120BaL (R5)	No	• Morphine (10 μM) • DAMGO	• Morphine ↑ astroglial CCL5 blocking gp120BaL neurotoxicity • Morphine (or CXCL12) does not block gp120IIIB neurotoxicity	Rat, mixed neurons and glia; isolated neurons, astrocytes and microglia	(Avdoshina et al. 2010)

^aassumed Clade B, unless noted otherwise, ^b statistical findings for some results are unclear

ARV, antiretroviral(s); BMVEC, brain vascular endothelial cells; [Ca²⁺]_i intracellular calcium concentration; 8-CAC, 8-carboxamidocyclazocine; DAMGO, D-Ala², N-MePhe⁴, Gly-ol]-enkephalin; DCF, dihydro-dichlorofluorescein; DOR, δ-opioid receptor; DHE, dihydroethidium; DTG, dolutegravir; DPDPE, [D-Pen²,D-Pen⁵]enkephalin; FTC, emtricitabine; GABA, γ-aminobutyric acid; Iba1, ionized calcium-binding adapter molecule 1; JAM-1, junctional adhesion molecule-1; KCC2, K⁺-Cl⁻ cotransporter 2; KOR, κ-opioid receptor; LTR, long terminal repeat; Δ_Ψm, mitochondrial inner membrane potential; MOR, μ-opioid receptor; [Na⁺]_i, intracellular sodium concentration; nor-BNI, nor-binaltorphimine; NPCs, neural progenitor cells; OLs, oligodendroglia; ROS, reactive oxygen species; TEER, transendothelial electrical resistance; TFV, tenofovir; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; ZDV, zidovudine

For practicality, the table is limited to key studies in the CNS with emphasis on neuropathological or neuroimmune rather than psychosocial outcomes. With deference toward the excellent studies we excluded: (1) on opioid and HIV effects on PBMCs, or on isolated lymphocytes and monocytes, not directly related to the central nervous system or BBB; (2) on HIV or opioid and ARV interactions in the peripheral nervous system; and (3) studies not directly examining opioid-HIV interactions (irrespective of whether a positive or negative interaction was found)