Methamphetamine alters the expression of Toll‐like receptor 4 on microglia‐like cells

Abstract

Methamphetamine (METH) is a major public health and safety problem in the United States. METH is a strong central nervous system (CNS) stimulant that mimics the pharmacological effects of cocaine. METH abuse can also alter biological processes and immune functions necessary for host defense. Microglia are key cellular mediators of the innate immune system in the CNS and can be activated by METH in a dose‐dependent manner through the Toll‐like receptor (TLR) 4/MD2 complex. This complex could also be stimulated in microglia by interactions with pathogen‐associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS) resulting in neuroinflammation and neuronal damage. Moreover, minocycline, a semi‐synthetic tetracycline derivative antimicrobial drug, inhibits microglial activation. Therefore, we hypothesized that METH impairs the microglial expression of TLR4. NR‐9460 cells, a murine microglial line derived from wild‐type mouse brain tissue, were treated with METH or minocycline for 2 h followed by incubation with LPS for 24 h. Then, flow cytometry, confocal microscopy, and western blot analyses were performed to determine the effect of METH on the expression of TLR4 receptors on microglia‐like cells. We found that METH alone increases the expression and distribution of TLR4 receptors on the surface of microglia‐like cells and changes the cellular morphology. Interestingly, after stimulation of METH–treated microglia with LPS, the TLR4 expression and distribution on the surface of these cells increases, however, the protein expression of the receptor showed no difference in total protein lysates. Our findings suggest that METH use may impair the cellular production of TLR4 in microglia. In fact, it is conceivable that METH interferes with the signaling pathways and inflammatory responses important to prevent and eradicate CNS infection. We believe this interdisciplinary project is of considerable significance in the fields of neurosciences, immunology, and drug abuse. We anticipate that our findings will result in a deeper understanding of neuroinflammation and CNS microbial infection control in METH users.Support or Funding InformationThis work was supported by NIGMS‐NIH grants: 1R15GM117501‐01A1 (LRM), and UPR‐Ponce Research Initiative for Scientific Enhancement (R25GM096955). The authors also acknowledge the support from the Border Biomedical Research Center (BBRC) at the University of Texas at El Paso (NIMHD Grant 2G12MD007592).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.