Cannabis Use by People with HIV is Associated with an Anti-Inflammatory Immunometabolic Phenotype in Monocyte-Derived Macrophages

This study demonstrates that daily cannabis use in people with HIV is associated with reduced neurocognitive deficits and an anti-inflammatory, neuroprotective immunometabolic reprogramming of monocyte-derived macrophages, characterized by a shift toward oxidative phosphorylation, increased mitochondrial numbers, and favorable cytokine and BDNF profiles.

The Gist

Important Context Upfront: Before diving into the story, it is crucial to understand that this study is an observational association, not a proven cause-and-effect relationship. The researchers found a link between daily cannabis use and better brain function in people with HIV, but they cannot yet say that cannabis caused the improvement. It is a strong clue that points toward a new way to understand brain health in HIV, but more research (like clinical trials) is needed to confirm the mechanism. Additionally, these effects were specific to people living with HIV; the results may not apply to people without HIV.

The Big Picture: A "Stressed" City and Its Security Guards

Imagine your body is a bustling city. Inside this city, there are special security guards called macrophages (specifically, monocyte-derived macrophages). Their job is to patrol the streets, clean up trash, and fight off invaders.

For people living with HIV, even those on successful medication that keeps the virus quiet, the city is under a state of constant, low-level emergency. This is due to chronic inflammation caused by the HIV infection itself and/or long-term exposure to antiretroviral therapy (ART). This stress causes the security guards to run on a "panic mode" energy system, creating a smog of inflammation that can cloud the city's brain, leading to memory lapses and trouble thinking (neurocognitive impairment).

The Question: Researchers noticed that some people with HIV who use cannabis seemed to have better brain function than those who didn't. This study set out to find out what was happening inside their cells to explain this observation.

The Discovery: What the Study Found

The researchers took blood samples from 50 people with HIV and 33 people without HIV. They grew the security guards (macrophages) in a lab and compared how they behaved based on the donors' habits: those who did not use cannabis versus those who used it daily.

Here is what they observed, using metaphors to visualize the differences:

1. The Energy Shift: From "Sugar Rush" to "Clean Fuel"

• What they observed in non-users: In people with HIV who did not use cannabis, the security guards were running on Glycolysis. Think of this like a car engine that only runs on cheap, sugary gas. It's fast and explosive, but it creates a lot of exhaust (inflammation) and overheats the engine. The guards appeared angry, loud, and prone to damaging the city.
• What they observed in daily cannabis users: In people with HIV who used cannabis daily, the guards appeared to be running on Oxidative Phosphorylation. This is like a high-efficiency hybrid engine. It runs cleaner, produces less exhaust, and generates more power. These guards appeared calmer, more efficient, and focused on repair rather than destruction.

2. The Power Plant Upgrade: More Batteries

• What they observed in non-users: The guards in non-users had fewer mitochondria (the cell's power plants). They were running on empty tanks, struggling to keep up with the demands of the stressed city.
• What they observed in daily cannabis users: The guards in daily cannabis users had more mitochondria. It looked as if their cells had installed more batteries. This extra power allowed them to handle the job of cleaning up inflammation without getting tired or angry.

3. The Message Board: Changing the Chatter

• What they observed in non-users: Without cannabis use, the guards were shouting "Attack!" messages (pro-inflammatory cytokines like IL-1 and IL-6). They were screaming at the brain cells, which can cause damage.
• What they observed in daily cannabis users: With daily cannabis use, the guards appeared to be whispering "Heal" messages (anti-inflammatory cytokines like IL-10). They also seemed to be producing more BDNF (Brain-Derived Neurotrophic Factor). Think of BDNF as "fertilizer" for the brain. It helps neurons grow new connections and stay healthy.

The Proof: What the Blood Tests Showed

The researchers didn't just look at the cells; they checked the "smoke" coming out of the city (the blood plasma).

• GDF15 & sTREM2: These are markers of stress and damage. In non-users, these were high (like a smoke alarm going off). In daily cannabis users, these levels were significantly lower.
• The Ratio: The balance of "healthy brain fertilizer" (mature BDNF) vs. "unprocessed fertilizer" (proBDNF) was much better in cannabis users. This difference correlated directly with better test scores on memory and thinking tasks.

The "Why" Matters: Context is King

The paper highlights a crucial point: These findings are specific to the context of HIV-related stress.

• In a healthy city (People without HIV): The study suggests that cannabis might not provide these benefits and could potentially confuse the guards or slow them down.
• In a stressed city (People with HIV): The city is already dealing with chronic inflammation. In this specific environment, daily cannabis use was associated with reduced inflammation and a shift in the immune system's behavior. It appeared to help calm the guards down, stop the screaming, and let them switch to "repair mode."

The Bottom Line

This study suggests that for people living with HIV, daily cannabis use is associated with an immune system shift: moving security guards from a "war mode" (which damages the brain) toward a "peace and repair mode" (which protects the brain).

It's as if, in this specific context, cannabis use was linked to hitting a "reset button" on the immune system, turning a chaotic, noisy construction site into a quiet, organized garden. This reprogramming is associated with less brain fog and better thinking skills.

Final Reminder: This is a strong clue, not a final prescription. The authors emphasize that this is an association, not proof that cannabis causes the improvement. More research is needed to be sure, and these results do not mean everyone should start using cannabis, as the effects can be very different for people without HIV.

Technical Summary

1. Problem Statement

Despite the success of Antiretroviral Therapy (ART) in managing HIV, People with HIV (PWH) face persistent chronic neuroinflammation and HIV-associated neurocognitive impairment (NCI). Monocyte-derived macrophages (MDMs) are critical mediators of this inflammation, often adopting a pro-inflammatory, glycolytic phenotype that damages neurons. While cannabis use is prevalent among PWH and has been associated with reduced neuroinflammation and better cognitive outcomes in some studies, the underlying cellular and molecular mechanisms remain unknown. Specifically, it is unclear how cannabis use influences the immunometabolic reprogramming of MDMs in the context of HIV.

2. Methodology

The study employed a cross-sectional design involving a cohort of 83 participants (50 PWH and 33 people without HIV [PWoH]), categorized by HIV status and cannabis use frequency (Naïve/Low, Moderate, Daily).

• Sample Collection: Venous blood was collected to isolate Peripheral Blood Mononuclear Cells (PBMCs).
• Cell Culture: Monocytes were differentiated into MDMs in vitro over 8 days.
• Experimental Treatments: MDMs were pre-treated with delta-9-tetrahydrocannabinol (THC) and subsequently stimulated with IL-1β (20 ng/mL) to induce inflammation.
• Assays Performed:
  • Immunocytochemistry: MitoTracker Deep Red staining to quantify mitochondrial number and signal intensity using high-content screening (CellInsight CX5).
  • Metabolic Profiling: Seahorse XF Analyzer to measure Extracellular Acidification Rate (ECAR, proxy for glycolysis) and Oxygen Consumption Rate (OCR, proxy for oxidative phosphorylation).
  • Transcriptomics: RNA sequencing (Illumina NovaSeq X Plus) and qPCR to analyze gene expression related to mitochondrial biogenesis, glycolysis, oxidative stress, cytokines, and neurotrophic factors.
  • Plasma Biomarkers: ELISA quantification of Growth Differentiation Factor 15 (GDF15), soluble TREM2 (sTREM2), mature BDNF (mBDNF), and proBDNF.
  • Clinical Assessment: Comprehensive neurocognitive testing to generate Global Deficit Scores (GDS) and domain-specific T-scores.

3. Key Contributions

This study provides the first mechanistic link between cannabis use, MDM immunometabolism, and neurocognitive outcomes in PWH. Key contributions include:

• Immunometabolic Reprogramming: Demonstrating that daily cannabis use shifts MDMs from a pro-inflammatory, glycolytic state to an anti-inflammatory, oxidative phosphorylation (OXPHOS)-dependent state.
• Mitochondrial Biogenesis: Identifying that cannabis use is associated with increased mitochondrial numbers and upregulation of PGC-1α (a master regulator of mitochondrial biogenesis).
• Biomarker Correlation: Validating cellular findings with plasma biomarkers (GDF15, sTREM2, BDNF) that correlate with improved cognitive performance.
• Context-Dependent Neuroprotection: Highlighting that the neuroprotective effects of cannabis appear specific to the pathological environment of HIV, potentially mitigating HIV-driven neuroinflammation rather than enhancing cognition in healthy individuals.

4. Key Results

A. Neurocognitive Outcomes

• Interaction Effect: There was a significant interaction between HIV status and cannabis use frequency regarding Global Deficit Scores (GDS).
• Findings: PWH who were cannabis-naïve/low exhibited significantly higher neurocognitive deficits compared to PWoH. However, daily cannabis use in PWH was associated with significantly fewer global neurocognitive deficits, bringing their performance closer to that of PWoH.
• Correlation: In cannabis-using PWH, higher mitochondrial signal in MDMs (post-THC exposure) positively correlated with better performance in executive function, motor skills, verbal ability, learning, and working memory.

B. Immunometabolic Phenotype in MDMs

• Metabolic Shift: Daily cannabis-using PWH showed a reduction in IL-1β-stimulated glycolysis (lower ECAR) and a shift toward oxidative phosphorylation (higher OXPHOS gene expression).
• Mitochondrial Health: Cannabis-using PWH had significantly higher mitochondrial numbers per cell compared to naïve PWH.
• Gene Expression:
  • Upregulated: Mitochondrial biogenesis genes (PGC-1α, PINK1), OXPHOS genes, anti-inflammatory cytokines (IL-10, IL-4, CD163), $\beta$-oxidation genes, and BDNF.
  • Downregulated: Pro-inflammatory cytokines (IL-1$\alpha$, IL-1$\beta$, IL-18), glycolytic genes (PGAM1, TPI1, GPI), and oxidative stress genes (HIF1$\alpha$, GPX3, SOD1).

C. Plasma Biomarkers

• Inflammation/Stress: Daily cannabis-using PWH had lower plasma levels of GDF15 (a marker of mitochondrial stress) and sTREM2 (a marker of neuroinflammation) compared to naïve PWH.
• Neuroprotection: Daily users showed a higher mBDNF/proBDNF ratio, which correlated with better cognitive scores (lower GDS).
• Correlations: Higher sTREM2 levels correlated with worse cognition, while higher mBDNF/proBDNF ratios correlated with better cognition.

5. Significance and Implications

• Mechanistic Insight: The study elucidates a potential mechanism where cannabis use mitigates HIV-associated NCI by reprogramming MDMs toward a "reparative" phenotype characterized by enhanced mitochondrial function and reduced inflammation.
• Therapeutic Potential: The findings suggest that targeting the endocannabinoid system (specifically CB2 receptors on macrophages) or mimicking the immunometabolic shift induced by cannabis could be a novel therapeutic strategy for HIV-associated neurocognitive disorders.
• Precision Medicine: The results support the hypothesis that cannabis may act as a "pathology-specific modulator," offering neuroprotection in the context of chronic neuroinflammation (HIV) without necessarily providing benefits (or potentially causing harm) in healthy individuals.
• Future Directions: The authors call for longitudinal studies and randomized controlled trials to confirm causality, refine dosing strategies, and explore non-psychoactive CB2-selective agonists as potential treatments for HIV-associated NCI.

Limitations: The study is cross-sectional (precluding causal inference), relies on self-reported cannabis use, has a relatively small sample size for some sub-analyses, and did not control for all potential confounders (e.g., polysubstance use, specific ART regimens).