Enduring changes in brain metabolites and executive functioning in abstinent cocaine users

Imaging neuroinflammation in individuals with substance use disorders

Increasing evidence suggests a role of neuroinflammation in substance use disorders (SUDs). This Review presents findings from neuroimaging studies assessing brain markers of inflammation in vivo in individuals with SUDs. Most studies investigated the translocator protein 18 kDa (TSPO) using PET; neuroimmune markers myo-inositol, choline-containing compounds, and N-acetyl aspartate using magnetic resonance spectroscopy; and fractional anisotropy using MRI. Study findings have contributed to a greater understanding of neuroimmune function in the pathophysiology of SUDs, including its temporal dynamics (i.e., acute versus chronic substance use) and new targets for SUD treatment.

Spectroscopic meta-analyses reveal novel metabolite profiles across methamphetamine and cocaine substance use disorder

BACKGROUND

Although proton magnetic resonance spectroscopy (MRS) has been used to study metabolite alterations in stimulant (methamphetamine and cocaine) substance use disorders (SUDs) for over 25 years, data-driven consensus regarding the nature and magnitude of these alterations is lacking.

METHOD

In this meta-analysis, we examined associations between SUD and regional metabolites (N-acetyl aspartate (NAA), choline, myo-inositol, creatine, glutamate, and glutamate+glutamine (glx)) in the medial prefrontal cortex (mPFC), frontal white matter (FWM), occipital cortex, and basal ganglia as measured by 1 H-MRS. We also examined moderating effects of MRS acquisition parameters (echo time (TE), field strength), data quality (coefficient of variation (COV)), and demographic/clinical variables.

RESULTS

A MEDLINE search revealed 28 articles that met meta-analytic criteria. Significant effects included lower mPFC NAA, higher mPFC myo-inositol, and lower mPFC creatine in SUD relative to people without SUD. mPFC NAA effects were moderated by TE, with larger effects at longer TEs. For choline, although no group effects were observed, effect sizes in the mPFC were related to MRS technical indicators (field strength, COV). No effects of age, sex, primary drug of use (methamphetamine vs. cocaine), duration of use, or duration of abstinence were observed. Evidence for moderating effects of TE and COV may have implications for future MRS studies in SUDs.

CONCLUSIONS

The observed metabolite profile in methamphetamine and cocaine SUD (lower NAA and creatine with higher myo-inositol) parallels that observed in Alzheimer's disease and mild cognitive impairment, suggesting these drugs are associated with neurometabolic differences similar to those characterizing these neurodegenerative conditions.

Important role of microglia in HIV-1 associated neurocognitive disorders and the molecular pathways implicated in its pathogenesis

The development of effective combined anti-retroviral therapy (cART) led to a significant reduction in the death rate associated with human immunodeficiency virus type 1 (HIV-1) infection. However, recent studies indicate that considerably more than 50% of all HIV-1 infected patients develop HIV-1-associated neurocognitive disorder (HAND). Microglia are the foremost cells infected by HIV-1 in the central nervous system (CNS), and so, are also likely to contribute to the neurotoxicity observed in HAND. The activation of microglia induces the release of pro-inflammatory markers and altered secretion of cytokines, chemokines, secondary messengers, and reactive oxygen species (ROS) which activate signalling pathways that initiate neuroinflammation. In turn, ROS and inflammation also play critical roles in HAND. However, more efforts are required to understand the physiology of microglia and the processes involved in their activation in order to better understand the how HIV-1-infected microglia are involved in the development of HAND. In this review, we summarize the current state of knowledge about the involvement of oxidative stress mechanisms and role of HIV-induced ROS in the development of HAND. We also examine the academic literature regarding crucial HIV-1 pathogenicity factors implicated in neurotoxicity and inflammation in order to identify molecular pathways that could serve as potential therapeutic targets for treatment of this disease. KEY MESSAGES Neuroinflammation and excitotoxicity mechanisms are crucial in the pathogenesis of HAND. CNS infiltration by HIV-1 and immune cells through the blood brain barrier is a key process involved in the pathogenicity of HAND. Factors including calcium dysregulation and autophagy are the main challenges involved in HAND.

Meta-analysis of brain metabolite differences in HIV infection

BACKGROUND

Numerous studies have used magnetic resonance spectroscopy (MRS) neurometabolite measurements to study HIV infection effects. While many have reported differences in total N-Acetylaspartate (tNAA), myo-Inositol (mI), and total Choline (tCho), there have been no meta-analyses performed to evaluate concordance across studies.

PURPOSE

To evaluate the consistency of HIV serostatus effects on brain metabolites.

STUDY SELECTION

The sample included studies conducted between 1993 and 2019 reporting HIV infection effects measured using proton MRS. tNAA/tCr ratios (21 papers), tCho/tCr ratios (21 papers), mI/tCr ratios (17 papers) and quantitative tCr (9 papers), sampling from basal ganglia (BG), gray matter (GM), and white matter (WM) were included.

DATA ANALYSIS

Random effects meta-analysis using inverse variance weighting and bias corrected standardized mean differences (SMDs) was used. Meta-regression examined effects of publication year and data acquisition technique differences.

DATA SYNTHESIS

BG SMDs related to positive serostatus were -0.10 [-0.39; 0.18] tNAA/tCr, 0.27 [0.05; 0.49] tCho/tCr, 0.60 [0.31; 0.90] mI/tCr, and -0.26 [-0.59; 0.06] tCr. GM SMDs related to serostatus were -0.29 [-0.49; -0.09] tNAA/tCr, 0.37 [0.19; 0.54] tCho/tCr, 0.41 [0.15; 0.68] mI/tCr, and -0.24 [-0.45; -0.03] tCr. WM SMDs related to serostatus were -0.52 [-0.79; -0.25] tNAA/tCr, 0.41 [0.21; 0.61] tCho/tCr, 0.59 [0.24; 0.94] mI/tCr, and -0.03 [-0.25; 0.19] tCr. WM regions showed larger serostatus effect sizes than BG and GM. I² ranged from 52 to 88% for the metabolite ratios. Both GM and WM tNAA/tCr SMDs were lower with increasing calendar year.

LIMITATIONS

Many studies pooled participants with varying treatment, infection, and comorbidity durations.

CONCLUSIONS

HIV neurometabolite studies showed consistently lower tNAA/tCr, higher tCho/tCr and higher mI/tCr ratios associated with chronic HIV infection. Substantial between-study variation may have resulted from measurement technique variations, study population differences and HIV treatment changes over time. Higher WM tCho/tCr and mI/tCr may reflect reactive gliosis or myelin turnover. Neurometabolite measurements can reliably detect chronic HIV infection effects and may be useful in understanding the pathophysiology of cognitive and sensorimotor decline following HIV infection.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence of neurometabolite differences in chronic HIV infection.

Behavioral and neurobiological alterations induced by chronic use of crack cocaine

Crack cocaine is the crystal form of cocaine and can be smoked, and rapidly absorbed, and, in part for this reason, is potently addictive. It is hypothesized that crack cocaine is able to induce important changes in different tissues and organs, and thus dramatically alter behavior. Nevertheless, which alterations in the central nervous system are related to its frequent use is still a matter of discussion. The present study is a literature review of articles published between the years 2008 and 2018 on the theme 'crack cocaine and brain' available in PUBMED, MEDLINE, EMBASE, and Google scholar databases. The results show that the use of crack cocaine induces important behavioral, neuroanatomical, and biochemical alterations. The main behavioral sequelae include cognitive and emotional changes, such as increased anxiety and depressive symptoms, attention and memory deficits, and hyperactivity. Among the neurobiological alterations are reductions in the activity of the prefrontal, anterior cingulate cortex, and nucleus accumbens. Molecular changes include decreases in neurotrophic factors and increases in oxidative stress and inflammatory cytokines, which may be responsible for the morphological alterations observed. It is also hypothesized that these neurobiological changes might explain the emotional and cognitive dysfunctions experienced by crack cocaine addicts.

HIV-1 infection alters energy metabolism in the brain: Contributions to HIV-associated neurocognitive disorders

The brain is particularly sensitive to changes in energy supply. Defects in glucose utilization and mitochondrial dysfunction are hallmarks of nearly all neurodegenerative diseases and are also associated with the cognitive decline that occurs as the brain ages. Chronic neuroinflammation driven by glial activation is commonly implicated as a contributing factor to neurodegeneration and cognitive impairment. Human immunodeficiency virus-1 (HIV-1) disrupts normal brain homeostasis and leads to a spectrum of HIV-associated neurocognitive disorders (HAND). HIV-1 activates stress responses in the brain and triggers a state of chronic neuroinflammation. Growing evidence suggests that inflammatory processes and bioenergetics are interconnected in the propagation of neuronal dysfunction. Clinical studies of people living with HIV and basic research support the notion that HIV-1 creates an environment in the CNS that interrupts normal metabolic processes at the cellular level to collectively alter whole brain metabolism. In this review, we highlight reports of abnormal brain metabolism from clinical studies and animal models of HIV-1. We also describe diverse CNS cell-specific changes in bioenergetics associated with HIV-1. Moreover, we propose that attention should be given to adjunctive therapies that combat sources of metabolic dysfunction as a mean to improve and/or prevent neurocognitive impairments.

NMDA receptor subunits change in the prefrontal cortex of pure-opioid and multi-drug abusers: a post-mortem study

Addiction is a chronic relapsing disorder and is one of the most important issues in the world. Changing the level of neurotransmitters and the activities of their receptors, play a major role in the pathophysiology of substance abuse disorders. It is well-established that N-methyl-D-aspartate receptors (NMDARs) play a significant role in the molecular basis of addiction. NMDAR has two obligatory GluN1 and two regionally localized GluN2 subunits. This study investigated changes in the protein level of GluN1, GluN2A, and GluN2B in the prefrontal cortex of drug abusers. The medial prefrontal cortex (mPFC), lateral prefrontal cortex (lPFC), and orbitofrontal cortex (OFC) were dissected from the brain of 101 drug addicts brains and were compared with the brains of non-addicts (N = 13). Western blotting technique was used to show the alteration in NMDAR subunits level. Data obtained using Western blotting technique showed a significant increase in the level of GluN1 and GluN2B, but not in GluN2A subunits in all the three regions (mPFC, lPFC, and OFC) of men whom suffered from addiction as compared to the appropriate controls. These findings showed a novel role for GluN1, GluN2B subunits, rather than the GluN2A subunit of NMDARs, in the pathophysiology of addiction and suggested their role in the drug-induced plasticity of NMDARs.