Go through the epidermis
Psoriasis is a chronic skin disease in which itchy, flaky lesions appear on the skin, affecting more than 8 million residents of the United States and 125 million people worldwide. Drugs based on small molecules, such as steroids, can penetrate the skin to treat this disease, but cause irritation and thinning of the skin, and their effectiveness may decrease over time. Antibodies have been developed that target specific inflammatory molecules associated with psoriasis, but since they cannot be delivered through the skin, they are injected, which limits use and can lead to negative side effects.
A group of researchers from Harvard University was able to overcome these limitations by using an ionic liquid to deliver small interfering RNA (miRNA). Applying the experimental drug to the skin of mice with psoriasis significantly reduced the level of inflammatory cytokines and symptoms of the disease without systemic side effects.
The path to success
Synthetic miRNAs are non-coding double-stranded RNA molecules that are commonly used in biological research to stop the expression of a target gene. This ability also makes them very attractive candidates for treating diseases and disorders without altering the DNA in the patient's cells. However, use in medicine is difficult because RNAs are large hydrophilic molecules, and it is difficult for them to cross the hydrophobic membranes of cells.
The research team solved this problem by using newly discovered ionic liquids, which are essentially salts that retain their liquid form at room temperature. Based on earlier studies on the interaction of ionic liquids with lipids, the researchers suggested that they could stabilize miRNAs and improve their penetration through the lipids of cell membranes, providing localized silence of genes.
When the "pure" miRNA was applied to the mouse skin, it was poorly absorbed (in the center). The complex with the ionic liquid CAGE+CAPA allowed to increase penetration into the epidermis (right). Source here and further: The Wyss Institute at Harvard University.
The group first created a library of various ionic liquids, then tested their combinations to see which ones had the most appropriate physical and chemical properties. They settled on a mixture of two liquids – CAGE (choline and geranium acid) and CAPA (choline and phenylpropanoic acid), which helped miRNA molecules maintain their structural integrity and led to enhanced penetration of miRNA into pig skin in vitro. When the researchers applied a mixture of CAGE+CAPA in the form of a thick liquid for topical application to the skin of live mice, they did not observe inflammation or irritation, which indicates its non-toxicity.
Various types of ions in the ionic liquid CAGE+CAPA (red, blue, purple) interact strongly with miRNA atoms (white), preserving its structure.
Since ionic liquids are a fairly new material, it is difficult to predict their interaction with the loads they are supposed to deliver. The researchers performed molecular dynamics simulations to understand how the CAGE+CAPA mixture would interact with miRNA and cell membranes at the molecular level. The data obtained as a result of modeling showed that this complex has high stability due to the strong chemical interactions of its components with RNA base pairs. In addition, during the simulation, the complex penetrated cell membranes more intensively, because ions in ionic liquids could gather close to each other, forming aggregates that increased the ability of the complex to destroy the membrane and ensure the delivery of miRNA.
Overcoming barriers
Armed with an effective delivery vehicle, the group combined it with a special miRNA that silences the NFKBIZ gene involved in the activation of a number of inflammatory molecules in psoriasis. They applied a mixture of CAGE+CAPA with miRNA to the skin of mice with a psoriasis-like condition for four days, then compared them with mice that received CAGE+CAPA without miRNA and mice without treatment.
Skin section of a mouse model of psoriasis before treatment (left) – inflammation; after applying ionic liquid without miRNA (center) – inflammation increased; after applying ionic liquid with miRNA (right) – inflammation decreased.
In mice treated with miRNAs inhibiting the NFKBIZ gene, compared with other experimental groups, there was a decrease in signs of psoriasis (epidermal thickening, skin discoloration, excessive keratin growth, redness and peeling). The group also recorded a significant decrease in the expression of NFKBIZ and other psoriasis-related genes in mouse skin cells, demonstrating for the first time that an ionic liquid with miRNA induces a therapeutic effect at both molecular and macroscopic levels, silencing the target gene in vivo.
The new ionic liquid-based delivery platform can be scaled and customized to interact with various therapeutic molecules, including DNA and antibodies, for transdermal drug delivery in the treatment of eczema and other skin diseases.
Article by A.Mandal et al. Treatment of psoriasis with NFKBIZ siRNA using topical ionic liquid formulations is published in the journal Science Advances.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of the Wyss Institute: Getting under the skin of psoriasis.