Anti-oxidant and anti-inflammatory Effects of Aerosolised microalgal-derived extracellular vesicles in Bronchial Epithelial-Macrophage Co-cultures at the Air-Liquid Interface

This study demonstrates that aerosolized nanoalgosomes derived from the marine microalga *Tetraselmis chuii* are non-cytotoxic, preserve epithelial barrier integrity, and effectively mitigate oxidative stress and inflammation in bronchial epithelial-macrophage co-cultures, highlighting their potential as a safe and sustainable therapeutic strategy for chronic inflammatory lung diseases.

The Gist

The Big Idea: A "Micro-Algae Shield" for Your Lungs

Imagine your lungs are a bustling city. The epithelial cells are the city walls (the barrier keeping the outside world out), and the macrophages are the police force patrolling the streets, ready to fight off invaders.

Sometimes, pollution, smoke, or viruses attack this city. This causes two big problems:

1. Oxidative Stress: Think of this as a "rusting" or "fire" inside the city walls. It damages the bricks and mortar.
2. Inflammation: This is the police force going into a panic. They start shouting, throwing things, and causing a riot (releasing inflammatory chemicals) that actually hurts the city more than the original threat.

Current medicines often just put out the fire or calm the police down temporarily, but they don't fix the root cause.

This paper introduces a new hero: Nanoalgosomes.

These are tiny, natural bubbles (vesicles) harvested from a microscopic green algae called Tetraselmis chuii. Think of them as tiny, natural "first-aid kits" floating in the air. Because they are so small, they can be turned into a mist (aerosol) and breathed in, landing directly on the lung city walls.

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How the Scientists Tested It

The researchers didn't just guess; they built a realistic model of the human lung in a lab.

• The Setup: They grew human lung cells (the walls) and immune cells (the police) on a special filter. They let the cells grow at the Air-Liquid Interface (ALI).
  • Analogy: Imagine a sponge sitting in a bowl of water, but the top of the sponge is exposed to air, just like your real lungs. This is much more realistic than keeping cells completely underwater.
• The Attack: They sprayed the lung model with two bad things:
  1. TBHP: A chemical that causes "rust/fire" (oxidative stress).
  2. LPS: A component of bacteria that triggers a massive "police riot" (inflammation).
• The Treatment: Before and during the attack, they sprayed the Nanoalgosomes onto the cells.

What Happened? (The Results)

The results were like a superhero movie where the hero saves the day:

1. The "First-Aid Kits" Were Safe
First, they checked if the Nanoalgosomes themselves were dangerous.

• Result: They were completely harmless. They didn't kill the cells or break the lung walls.
• Analogy: It's like sending in a team of friendly medics who don't accidentally step on the civilians while trying to help.

2. They Stopped the "Rust" (Oxidative Stress)
When the cells were attacked by the "rust" chemical, they usually get very damaged.

• Result: The cells that had been primed with Nanoalgosomes had 46% to 55% less damage.
• Analogy: Imagine the Nanoalgosomes are like a rust-proof coating or a fire extinguisher. When the fire started, the coated cells barely got singed, while the uncoated cells burned.

3. They Calmed the "Police Riot" (Inflammation)
When the bacteria signal (LPS) arrived, the immune cells usually scream and release a flood of angry chemicals (cytokines like IL-1β, TNF-α).

• Result: The Nanoalgosomes acted like a wise diplomat. They didn't stop the police from working, but they told them to "calm down." The amount of angry shouting (inflammatory chemicals) dropped significantly.
• Analogy: Instead of a chaotic riot, the police force organized themselves efficiently. They dealt with the threat without destroying the city in the process.

4. They Kept the City Walls Intact
The most important job of the lung is to keep a tight seal so bad stuff doesn't leak in.

• Result: Even under attack, the Nanoalgosome-treated cells kept their walls strong and tight.
• Analogy: While other cells' walls crumbled under pressure, the Nanoalgosome-treated walls held firm, like a reinforced fortress.

Why Is This a Big Deal?

1. It's Natural: These aren't synthetic chemicals made in a lab; they come from algae, which is a sustainable, renewable resource.
2. It's Smart: Because they are tiny bubbles (vesicles), they can carry their own "medicine" inside them. They are like delivery trucks that naturally contain the cargo needed to fix the problem.
3. It's Direct: You can breathe them in. This means the medicine goes straight to the lungs, rather than going through the whole body (which causes side effects).

The Bottom Line

This study shows that Nanoalgosomes are a promising new way to treat chronic lung diseases like asthma, COPD, and fibrosis.

Think of them as tiny, natural bodyguards for your lungs. When you breathe them in, they coat your lung cells, protect them from pollution and smoke, and teach your immune system how to fight back without causing a riot. It's a safe, sustainable, and effective way to keep your lung city healthy and running smoothly.

Technical Summary

1. Problem Statement

Chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis are driven by persistent inflammation and oxidative stress. These factors lead to airway remodeling, epithelial barrier dysfunction, and immune dysregulation. Current therapeutic strategies often provide only symptomatic relief and fail to address the underlying cellular drivers. Furthermore, there is a lack of research on natural nanotherapeutics delivered via aerosol in physiologically relevant models that mimic the human airway (specifically the Air-Liquid Interface or ALI). Most existing studies rely on simple submerged monocultures, which do not accurately recapitulate the complex interactions between bronchial epithelial cells and macrophages found in the lung.

2. Methodology

The study utilized a multi-step approach to characterize and test nanoalgosomes (extracellular vesicles derived from the marine microalga Tetraselmis chuii).

• Nanoalgosome Production & Characterization:

  • Source: Axenic cultures of T. chuii were grown and processed using Tangential Flow Filtration (TFF) with a three-stage protocol (650 nm, 200 nm, and 500 kDa MWCO) to isolate small EVs.
  • Quality Control: The vesicles were characterized using:
    • Nanoparticle Tracking Analysis (NTA): Confirmed size (~123 nm modal) and concentration.
    • Dynamic Light Scattering (DLS): Verified hydrodynamic diameter and polydispersity.
    • Atomic Force Microscopy (AFM): Visualized morphology.
    • Immunoblotting: Detected canonical EV markers (H⁺-ATPase, Alix).
    • Zeta Potential: Measured surface charge (-30 mV).
    • DetectEV Assay: Verified membrane integrity and intraluminal esterase activity.

• In Vitro Model (ALI Co-culture):

  • Cell Lines: Human bronchial epithelial cells (CALU-3) and differentiated human macrophages (THP-1, induced by PMA).
  • Setup: CALU-3 cells were seeded on Transwell inserts and grown to confluence. Differentiated THP-1 macrophages were seeded on the apical surface to create a co-culture.
  • Conditions: Cultures were maintained at the Air-Liquid Interface (ALI) to mimic the respiratory tract environment.

• Aerosolization & Treatment:

  • Delivery: Nanoalgosomes were nebulized using a VITROCELL® Cloud Alpha 6 system for uniform deposition.
  • Priming: Co-cultures were primed with aerosolized nanoalgosomes.
  • Stressors:
    • Oxidative Stress: Induced by tert-butyl hydroperoxide (TBHP) (1 mM) for 4 and 24 hours.
    • Inflammation: Induced by nebulized Lipopolysaccharide (LPS) (125 and 250 µg/mL) for 24 hours.
  • Controls: Solvent controls (SC) and incubator controls (IC) were used.

• Assays:

  • Cytotoxicity: Lactate Dehydrogenase (LDH) release.
  • Barrier Integrity: Transepithelial Electrical Resistance (TEER).
  • Oxidative Stress: Intracellular Reactive Oxygen Species (ROS) via H2DCFDA fluorescence.
  • Immunomodulation: Quantification of cytokines (IL-1β, IL-6, IL-8, IL-10, IL-18, TNF-α) via ELISA and Luminescent ELISA.

3. Key Contributions

• Physiologically Relevant Model: The study moves beyond simple monocultures by utilizing a bronchial epithelial–macrophage co-culture at the ALI, providing a more accurate representation of lung pathophysiology.
• Aerosol Delivery Validation: It demonstrates the feasibility and efficacy of delivering natural EVs via aerosolization, a critical step for developing inhalable therapies for respiratory diseases.
• Dual-Action Mechanism: The research establishes that nanoalgosomes possess intrinsic antioxidant and immunomodulatory properties without the need for drug encapsulation.
• Safety Profile: Comprehensive data confirms the biocompatibility and non-cytotoxic nature of T. chuii-derived EVs in a complex airway model.

4. Key Results

• Characterization: Nanoalgosomes were confirmed as small EVs (modal size ~123 nm) with a negative zeta potential (-30 mV) and high purity, retaining bioactive esterase activity.
• Biocompatibility:
  • Nanoalgosome priming alone caused no cytotoxicity (LDH release) and did not disrupt epithelial barrier integrity (TEER remained stable).
  • They did not exacerbate damage caused by TBHP or LPS.
• Antioxidant Effects:
  • TBHP exposure caused a ~4.8-fold increase in intracellular ROS at 4 hours.
  • Nanoalgosome priming reduced ROS accumulation by 46% at 4 hours and 55% at 24 hours compared to TBHP-only groups, demonstrating sustained protection against oxidative stress.
• Anti-inflammatory Effects:
  • LPS nebulization significantly increased pro-inflammatory cytokines (IL-1β, IL-18, TNF-α).
  • Nanoalgosome priming significantly attenuated these responses:
    • IL-1β: Reduced ~1.6-fold.
    • IL-18: Reduced ~2.2-fold.
    • TNF-α: Reduced ~3.6-fold (at 250 µg/mL LPS).
  • IL-10 (Anti-inflammatory): LPS induced a compensatory rise in IL-10; nanoalgosomes normalized this, preventing excessive compensatory signaling and promoting immune homeostasis.
  • IL-6 and IL-8 showed modest increases with LPS, which were also attenuated by priming.

5. Significance

• Therapeutic Potential: Nanoalgosomes represent a promising, sustainable, and scalable class of inhalable biotherapeutics for chronic lung diseases (asthma, COPD, fibrosis).
• Mechanism of Action: The protective effects are likely attributed to the rich cargo of T. chuii (carotenoids, polyphenols, PUFAs) which modulate redox balance and inflammatory signaling pathways (e.g., NF-κB, MAPK).
• Clinical Relevance: The ability to deliver these natural nanocarriers via aerosol directly to the lung offers a targeted approach with minimal systemic side effects, potentially outperforming or complementing current symptomatic treatments.
• Future Outlook: This work lays the foundation for preclinical inhalation studies to validate pharmacokinetics, dosing, and long-term safety, bridging the gap between natural bioactive compounds and next-generation pulmonary medicine.