Dysregulation of macrophage-secreted cathepsin B contributes to HIV-1-linked neuronal apoptosis.
Chronic HIV infection leads to the development of cognitive impairments, designated as HIV-associated neurocognitive disorders (HAND). The secretion of soluble neurotoxic factors by HIV-infected macrophages plays a central role in the neuronal dysfunction and cell death associated with HAND. One potentially neurotoxic protein secreted by HIV-1 infected macrophages is cathepsin B. To explore the potential role of cathepsin B in neuronal cell death after HIV infection, we cultured HIV-1(ADA) infected human monocyte-derived macrophages (MDM) and assayed them for expression and activity of cathepsin B and its inhibitors, cystatins B and C. The neurotoxic activity of the secreted cathepsin B was determined by incubating cells from the neuronal cell line SK-N-SH with MDM conditioned media (MCM) from HIV-1 infected cultures. We found that HIV-1 infected MDM secreted significantly higher levels of cathepsin B than did uninfected cells. Moreover, the activity of secreted cathepsin B was significantly increased in HIV-infected MDM at the peak of viral production. Incubation of neuronal cells with supernatants from HIV-infected MDM resulted in a significant increase in the numbers of apoptotic neurons, and this increase was reversed by the addition of either the cathepsin B inhibitor CA-074 or a monoclonal antibody to cathepsin B. In situ proximity ligation assays indicated that the increased neurotoxic activity of the cathepsin B secreted by HIV-infected MDM resulted from decreased interactions between the enzyme and its inhibitors, cystatins B and C. Furthermore, preliminary in vivo studies of human post-mortem brain tissue suggested an upregulation of cathepsin B immunoreactivity in the hippocampus and basal ganglia in individuals with HAND. Our results demonstrate that HIV-1 infection upregulates cathepsin B in macrophages, increases cathepsin B activity, and reduces cystatin-cathepsin interactions, contributing to neuronal apoptosis. These findings provide new evidence for the role of cathepsin B in neuronal cell death induced by HIV-infected macrophages.
Department of Microbiology and Medical Zoology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico.
Eillen J
EJ
Rodriguez-Franco
Yisel M
YM
Cantres-Rosario
Marines
M
Plaud-Valentin
Rafael
R
Romeu
Yolanda
Y
Rodríguez
Richard
R
Skolasky
Viviana
V
Meléndez
Carmen L
CL
Cadilla
Loyda M
LM
Melendez
D017209:Apoptosis; D001479:Basal Ganglia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000821:virology; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003071:Cognition; D055313:Cystatin B / Q000235:genetics / Q000378:metabolism; D055316:Cystatin C / Q000235:genetics / Q000378:metabolism; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015497:HIV-1 / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000821:virology; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism / Q000821:virology; D008247:Lysosomes / Q000378:metabolism / Q000821:virology; D008264:Macrophages / Q000378:metabolism* / Q000821:virology; D009000:Monocytes / Q000166:cytology; D009474:Neurons / Q000166:cytology* / Q000821:virology*
D055316:Cystatin C; D055313:Cystatin B; D002401:Cathepsin B