Parallel Effects of Methamphetamine on Anxiety and CCL3 in Humans and a Genetic Mouse Model of High Methamphetamine Intake

Abstract

Background: Methamphetamine (MA) abuse causes immune dysfunction and neuropsychiatric impairment. The mechanisms underlying these deficits remain unidentified.

Methods: The effects of MA on anxiety-like behavior and immune function were investigated in mice selectively bred to voluntarily consume high amounts of MA [i.e., MA high drinking (MAHDR) mice]. MA (or saline) was administered to mice using a chronic (14-day), binge-like model. Performance in the elevated zero maze (EZM) was determined 5 days after the last MA dose to examine anxiety-like behavior. Cytokine and chemokine expressions were measured in the hippocampus using quantitative polymerase chain reaction (qPCR). Human studies were also conducted to evaluate symptoms of anxiety using the General Anxiety Disorder-7 Scale in adults with and without a history of MA dependence. Plasma samples collected from human research participants were used for confirmatory analysis of murine qPCR results using an enzyme-linked immunosorbent assay.

Results: During early remission from MA, MAHDR mice exhibited increased anxiety-like behavior on the EZM and reduced expression of chemokine (C-C motif) ligand 3 (ccl3) in the hippocampus relative to saline-treated mice. Human adults actively dependent on MA and those in early remission had elevated symptoms of anxiety as well as reductions in plasma levels of CCL3, relative to adults with no history of MA abuse.

Conclusions: The results highlight the complex effects of MA on immune and behavioral function and suggest that alterations in CCL3 signaling may contribute to the mood impairments observed during remission from MA addiction.

Keywords: Anxiety; Genetic model; Hippocampus; Humans; Immune system; Methamphetamine; Rodents.

Fig. 1

MAHDR mice exhibit increased anxiety-like behavior following MA. a MA-exposed MAHDR mice spent less time in the open arms of the EZM, relative to saline-treated control MAHDR mice. MA- and saline-exposed MAHDR mice make a similar number of crossovers between the closed and open portions of the EZM (b) and exhibit a similar velocity (c) in the EZM. n = 8–9 mice per group, tested in 2 passes of 4–5 mice per group; **p < 0.01, unpaired t test.

Fig. 2

Adults with a history of MA abuse exhibit increased anxiety, paralleling results for an animal line with high genetic susceptibility for MA intake. Adults in the MA-ACT and MA-REM groups reported increased anxiety as determined from the GAD-7 questionnaire relative to the CTL group. The ACT group also had increased anxiety relative to the REM group. *p < 0.05, ***p < 0.001 using post hoc Sidak multiple comparisons.

Fig. 3

MA exposure reduces ccl3 expression in the mouse hippocampus and CCL3 concentration in human plasma. a MA exposure reduced levels of ccl3 in the hippocampus in MAHDR mice (n = 7 mice per group). Gene expression results were normalized to GAPDH values, and the data are shown as n-fold change from the MAH-DR CTL mice. *p < 0.05 using an unpaired 2-tailed t test. b Plasma levels of CCL3 were evaluated using ELISA. Adults actively dependent on MA and those in early remission had reductions in plasma levels of CCL3 relative* to the CTL group. *p < 0.05 using post hoc Sidak multiple comparisons.

Fig. 4

In humans, plasma CCL3 concentration does not recover with abstinence. Plasma levels of CCL3 were plotted relative to each participant’s reported number of days since last use of MA. No significant relationship between these parameters was observed, indicating that there was no evidence that CCL3 levels recovered following up to 180 days of abstinence. The dotted line represents the mean CCL3 concentration for the control (CTL) group (362.18 pg/mL). Linear regression: r² = 0.05, slope = −1.14, p = 0.18.