Discover the groundbreaking inhalable nanozyme therapy that’s set to revolutionize viral pneumonia treatment, offering broad-spectrum effects and reduced inflammation.

Study: Inhalable nanocatalytic therapeutics for viral pneumonia. Image Credit: Shutterstock AI / Shutterstock.com

A recent study published in the journal Nature Materials discusses the development of an inhalable nanozyme-based treatment for pneumonia.

The global burden of pneumonia

Current estimates indicate that about 200 million cases of pneumonia are diagnosed each year, with over two million individuals succumbing to this disease in 2022 worldwide. Viral pneumonia, which is common and highly contagious, arises after viral entry into cells, leading to the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (Nox2).

Nox2 activity leads to the generation of reactive oxygen species (ROS), which is often accompanied by a cascade of inflammatory cytokine release. This inflammatory response can lead to acute respiratory distress syndrome (ARDS), which may damage the heart muscle and increase the risk of respiratory failure.

Various antiviral drugs, including broad-spectrum viral nucleic acid polymerase analogs and those targeting host proteins, can be used to inhibit viral replication in this form of pneumonia. However, these agents may not be effective against new and emerging viruses, as evident early in the coronavirus disease 2019 (COVID-19) pandemic.

The use of natural enzymes to scavenge ROS in pneumonia has largely failed due to lung topology and enzyme-inactivating inflammatory immune responses. As a result, researchers have investigated the potential of nanozymes that can substitute for their natural counterparts.

Nanozymes have been explored for their utility in multiple inflammatory disorders affecting the neurologic and skeletal systems, as well as various infections. Traditional cerium-based nanozymes are associated with limited biosafety, as their long half-lives allow them to persist for at least 28 days in acidic conditions.

In vitro findings

The current study discusses the use of engineered cerium-based tannic acid (CeTA) nanozymes linked to a self-assembling peptide GGKLVF in an inhalable nasal formulation designed for the treatment of viral pneumonia. This molecule, eTA-GGGKLVFF-tk-PEG, which has been abbreviated to CeTA-K1tkP, consists of the CeTA and K1 peptide with a thioketal (tk) linker and polyethylene glycol (PEG).

Compared to traditional CeO₂ nanozymes, about 70% of CeTA breaks down over 28 days at acidic pH. Furthermore, CeTA remains physiologically stable under multiple conditions and is safer for therapeutic applications.

CeTA functions efficiently as an enzyme and free radical scavenger of hydroxyl (OH) and superoxide (O₂^–). Furthermore, CeTA exhibits catalase- and superoxide dismutase (SOD)-like activity that increases in a dose-dependent manner.

The presence of CeTA in oxidatively stressed cells led to a concentration-dependent attenuation of ROS while also protecting cell viability and reducing inflammatory factor levels following lipopolysaccharide (LPS) stimulation. Cells incubated with CeTA, even at high concentrations, maintained viability, thus indicating excellent biocompatibility.

The self-assembling peptide GGKLVFF-tk-PE forms aggregates in response to an oxidative environment, such as that which arises in the human lung and bronchial epithelial cells inflamed by LPS exposure. The tk linker connects the peptide and PEG molecule, with the addition of the modified CeTA nanozyme leading to self-assembled CeTA-K1tkP formation.

In vivo results

LPS-induced pneumonia

In mice with LPS-induced pneumonia, the ROS-rich environment led to nanozyme accumulation in the inflamed areas, which subsequently induced its enzymatic activity. This successfully attenuated ROS levels and decreased inflammatory cytokine release.

Viral influenza A pneumonia  

These findings were validated in a viral influenza A pneumonia mouse model, thus demonstrating its broad-spectrum effect. CeTA-K1tkP-treated mice experienced effective relief of inflammation and reduced viral load.

Sendal virus pneumonia

The efficacy of the nanozyme in relieving inflammation was further demonstrated in a Sendal virus pneumonia model. Herein, redox homeostasis was restored by increasing the expression of the Nrf2 gene, the main antioxidant pathway regulator, thereby preventing its inhibition by oxidative stress. Molecular docking simulations and titration experiments demonstrated that CeTA-K1tkP binds to the cell attachment proteins of both influenza A and Sendal viruses.

CeTA-K1tkP was phagocytosed by activated macrophages and alveolar epithelial cells at the sites of tracheal and lung inflammation. This caused macrophage activity to transition to the anti-inflammatory M2 phenotype and modulate neutrophil infiltration. Taken together, these changes indicate that CeTA-K1tkP can inhibit lung damage and immune-related disorders due to viral lung infection.

Viral pneumonia complicated by secondary bacterial infection

In an animal model with viral pneumonia complicated by secondary bacterial infection, CeTA-K1tkP weakened the intensity of inflammation, reduced cytokine release, prevented neutrophil recruitment, and promoted M2 macrophage shift. Since these co-infections are commonly reported in hospital settings and complicate treatment approaches, this promising observation may significantly impact future clinical applications.

In all models, no toxicity was observed.

How the nanozyme acts

At inflamed sites, cleavage of the linker causes PEG release, which forms beta-sheet protein aggregates of the peptides. The CeTA nanozyme is activated, thereby degrading ROS and reducing inflammation.

Conclusions

Overall, this nanozyme platform is a promising strategy for treating pneumonia and its associated conditions.”

CeTA-K1tkP has the potential to reduce inflammatory tissue damage in a variety of infections and conditions, including COVID-19, sepsis, arthritis, and enteritis.

In the future, other nanoparticles with catalytic or therapeutic properties, including antibiotics, immunotherapy molecules, and hormones, could replace the CeTa nanozymes in this formulation to improve their targeted delivered action and prevent toxicity due to adverse effects.