Tokai University group counters cytokine storms using extracellular vesicles

A research group including Visiting Researcher Shunya Nakayama at Tokai University School of Medicine (currently Assistant Professor at the College of Bioresource Sciences, Nihon University), Special Appointed Researcher Akane Kanamori (JSPS Research Fellow PD), Assistant Professor Takeshi Kamakura, and Professor Ai Kotani at the Research Institute for Microbial Diseases, the University of Osaka, in collaboration with the University of Tokyo and the University of Tsukuba, clarified that "SPLEVs," developed by processing hepatocyte-derived extracellular vesicles (EVs), possess powerful therapeutic effects against lethal cytokine storm. It was confirmed in lung inflammation in mice that large amounts of lipids quelling excessive inflammation are produced. They also confirmed that artificially produced "PG-SPLEVs" possess equivalent effects. Practical application as an innovative therapeutic drug for cytokine storm is expected. The findings were published in Science Advances on July 31.

A cytokine storm, where inflammatory cytokines are released due to excessive immune system response caused by infectious diseases or trauma, induces respiratory failure or multiple organ failure, serving as a larger threat and main cause of death than the cause of infectious diseases itself. While immunosuppressive therapy is applied to suppress this, sufficient effects are often not obtained, and development of new therapeutic methods is demanded. EVs, also called exosomes, are involved in intercellular communication, and research is advancing as anti-inflammatory effects are recognized.

Previously, the research group reported that hepatocyte-derived EVs have high therapeutic effects against inflammation, and that SPLEVs, created by artificially modifying the surface of liposome membranes containing EVs with secreted phospholipase A₂ (sPLA₂) that degrades EVs, possess high delivery capability and anti-inflammatory action.

Therefore, this time, the research group intravenously administered SPLEVs to mice in which severe lethal lung injury (lung inflammation) was induced with drugs and compared the results with administration of anti-inflammatory extracellular vesicles (LPS) via conventional methods.

In these mice, if untreated, neutrophils (immune cells) infiltrate and alveolar tissue is lethally destroyed. In contrast, in the SPLEVs administration group, infiltration of neutrophils dramatically decreased, and alveolar structure improved to a state close to normal. Conventional methods also partially improved but did not reach the SPLEVs group.

Investigating this mechanism, it was found that SPLEVs act directly on type II alveolar epithelial cells constituting alveoli. When taken into cells, master transcription factor SREBP1 controlling fat synthesis is strongly activated via the PI3K-AKT pathway, with the action of this factor producing large amounts of lipid mediators derived from polyunsaturated fatty acids (PUFA) that protect cells and converge inflammation. Through this, it was found that cytokine storms are neutralized. The research group named this lipid response, a new anti-inflammatory concept, "lipid counter-storm."

Next, to verify effects on diseases other than lung conditions, SPLEVs were administered to model mice with various diseases such as severe sepsis, severe viral pneumonia (influenza), and ulcerative colitis.

As a result, improvement of pathological conditions and significant extension of survival periods were confirmed in all cases. In addition, no immunosuppressive effects were recognized in any of them. Furthermore, to solve instability in production via cell culture, artificial synthesis of SPLEVs was examined.

Clarifying that the core component exerting effects is lysophosphatidylglycerol (LPG), they succeeded in producing artificial SPLEVs (PG-SPLEVs). Together, they also confirmed that it shows effects equivalent to SPLEVs. LPG is generated via enzymatic degradation of phospholipids contained abundantly in extracellular vesicles.

Both SPLEVs and PG-SPLEVs do not perform immunosuppression, unlike conventional anti-inflammatory drugs such as steroids or antibody drugs, confirming high therapeutic effects against cytokine storm. Because PG-SPLEVs can be mass-produced and are inexpensive, they are expected to enable a rapid response to pandemics.

Nakayama said "Because artificial SPLEVs can be purified, I think it can be said that there is possibility for social implementation as a next-generation all-round anti-inflammatory drug that can be mass-supplied inexpensively, serving as a shield to protect humanity from future pandemics."

Kotani stated, "Because SPLEVs preserve to some extent even at room temperature, I think usability is high without choosing usage locations under pandemics. We aim for formulation not only for cytokine storm but as a therapeutic drug for diseases where therapeutic drugs are currently demanded, such as intractable interstitial pneumonia and ulcerative colitis. We will work diligently toward social implementation, so we hope pharmaceutical manufacturers in Japan become aware of this technology."

Journal Information
Publication: Science Advances
Title: sPLA₂-reacted extracellular vesicles (SPLEVs) as a therapeutic modality for cytokine storm syndromes
DOI: 10.1126/sciadv.adr9135