Protein affinity reagents are widely used for basic research, diagnostics, and disease therapy. Antibodies and their fragments are known as the most common protein affinity reagents. They specifically and strongly bind to target molecules and inhibit their functions. Thus, antibody drugs have increased in the recent two decades for disease therapy, such as cancer. These strong protein–protein interactions are composed of a nexus of multiple weak interactions. Synthetic polymers that bind to target molecules have been developed by the imitation of protein–protein interactions. These polymers show nanomolar affinity for the target and neutralize their functions; thus, they are of significant interest as a cost-effective protein affinity reagent. We have been developing synthetic polymer nanoparticles (NPs) that bind to target peptides and proteins by the inclusion of several functional monomers, such as charged and hydrophobic monomers. In this review, the focus is on the design of synthetic polymer NPs that bind to target molecules for disease therapy. We succeeded in neutralization of toxic peptides and signaling proteins both in vitro and in vivo. Additionally, linear polymers were modified on a lipid nanoparticle surface to improve polymer biodistribution. Our recent findings should provide useful information for the development of abiotic protein affinity reagents.

Vitamin K2 is suggested to have a suppressive effect on the peripheral blood mononuclear cells (PBMCs) of pediatric atopic dermatitis patients. We examined the molecular targets of vitamin K2 to suppress proliferation and cytokine production in T-cell mitogen-activated PBMCs of atopic dermatitis patients from the viewpoint of mitogen-activated protein kinase signaling molecules. The study population included 16 pediatric vitamin K2 patients and 21 healthy subjects. The effect of vitamin K2 on concanavalin A-activated PBMC proliferation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell counting assays. T-helper (Th)1/Th2/Th17 cytokine profiles in plasma and PBMC-culture supernatants were analyzed by a cytometric beads array assay. Mitogen-activated protein kinase signaling molecules in concanavalin A-activated PBMCs were examined by enzyme-linked immunosorbent assay (ELISA) assays. At 10–100 µM, vitamin K2 significantly suppressed the proliferation of mitogen-activated PBMCs derived from atopic dermatitis patients and healthy subjects (p < 0.05). The interleukin (IL)-10 concentrations in plasma and the PBMC culture supernatants of atopic dermatitis patients were significantly higher than those of healthy subjects (p < 0.05). The IL-2 concentrations in the culture supernatants of atopic dermatitis PBMCs were significantly lower than those of healthy PBMCs (p < 0.05). Vitamin K2 significantly inhibited the IL-17A, IL-10, and tumor necrosis factor α (TNF-α) production (p < 0.05), and increased the IL-2 production (p < 0.01) in the culture supernatant of atopic dermatitis PBMCs. At 10–100 µM, vitamin K2 markedly decreased the of Mek1, extracellular signal-regulated kinases (ERK)1/2 mitogen-activated protein kinase, and SAPK/c-Jun N-terminal kinase (JNK) expression in atopic dermatitis PBMCs (p < 0.05). Vitamin K2 is suggested to attenuate activated T-cell immunity in atopic dermatitis patients through the inhibition of mitogen-activated protein kinase-Mek1-ERK1/2 and SAPK/JNK signaling pathways.

Deeper wrinkles and loss of elasticity are one of the skin-aging symptoms. Collagen breakdown by matrix metalloproteinase-1 (MMP-1), which is induced by reactive oxygen species (ROS) and pro-inflammatory cytokines, has been known to be responsible for these skin-aging symptoms. Therefore, much attention has been paid to chemicals to suppress the MMP-1 activity. Epigallocatechin-3-gallate (EGCG), catechin rich in green tea, has been reported to show antioxidant and protect skin from various stimuli such as UV and chemicals. In this study, we evaluated the inhibitory effect of EGCG on MMP-1 gene expression and secretion in tumor necrosis factor-α (TNF-α)-treated human dermal fibroblast cells (Hs68 cells). Pre-treatment with EGCG (10 and 20 µM) suppressed TNF-α-induced MMP-1 expression and secretion. EGCG also reduced the phosphorylation of extracellular signal regulated kinase (ERK) significantly but not that of p38 activation and c-Jun N-terminal kinase (JNK). Besides, EGCG (10 and 20 µM) showed the inhibitory effect on mitogen-activated protein extracellular kinase (MEK) and Src phosphorylation which is reported to be upstream signal proteins of ERK signal pathway. Based on these results, EGCG might have potential activity to slow down the skin-aging through inhibition of collagen breakdown, which remains to be elucidated.

Ischemia/reperfusion injury (IRI), a participant in acute kidney injury (AKI), can occur as a series of pathological processes such as inflammation. Linarin (LIN) has been widely used for different diseases. To confirm the anti-inflammatory value and relevant mechanism of LIN during IRI, in vivo and vitro models were established. LIN or dissolvent was given, and histologic analysis, quantitative (q)RT-PCR, serum creatinine and blood urea nitrogen testing were used to evaluate kidney injury. Microarray analysis, protein–protein interaction (PPI) analysis and molecular docking were used to identify the target protein of LIN, and small interfering RNA (siRNA) transfection was applied to explore the crucial role of identified protein. First, we found that LIN inhibited kidney injury in an in vivo IRI model and decreased the expression of interleukin-12 (IL-12) p40 in vivo and in vitro IRI models. To explore the mechanism of LIN, we collected raw data from a public microarray database and identified E26 oncogene homolog 2 (ETS2) as a crucial protein of LIN according to microarray analysis and PPI. Meanwhile, qRT-PCR indicated that IL-12 p40 showed no significant difference between ETS2 knock down group and LIN treated ETS2 knock down group after hypoxia reoxygenation treatment. In addition, according to molecular docking the contact area is highly conserved and located on a PPI domain of ETS2 which indicates that LIN may alter the interaction with synergistic proteins in the regulation of IL-12 p40 expression. Our study demonstrated the anti-inflammatory effect of LIN during IRI-AKI, broadening the medicinal value of LIN and the therapeutic options for IRI-AKI.

Sarcopenia is a disease whose symptoms include decreased muscle mass and weakened muscle strength with age. In sarcopenia, decreased production of insulin-like growth factor-1 (IGF-1) increases ubiquitin ligases, such as Atrogin1 and Muscle RING-Finger Protein-1 (MuRF1), by activating forkhead box O (FOXO), and inflammatory cytokines and oxidative stress increase the expression of ubiquitin ligases by activating the transcription factor nuclear factor-kappa B (NF-κB). In addition, increased levels of ubiquitin ligases cause skeletal muscle atrophy. Conversely, sirtuin 1 (Sirt1) is known to regulate the expression of ubiquitin ligases by suppressing the activities of NF-κB and FOXO. In this study, we evaluated the effect that juzentaihoto hot water extract (JTT) has on skeletal muscle atrophy and motor function by administering it to senescence-accelerated mouse prone-8 (SAMP8). The group treated with JTT displayed larger gastrocnemius muscle (GA) and extensor digitorum longus (EDL) weights, larger GA muscle fiber cross-sectional areas, and motor function decline during rota-rod tests. JTT also increased IGF-1 serum levels, as well as mRNA Sirt1 levels in GA. Serum levels of tumor necrosis factor-α, interleukin-6, and mRNA levels of Atrogin1 and MuRF1 in GA were reduced by JTT. The muscle fiber cross-sectional area of GA was correlated with the mRNA levels of Sirt1 in GA. The results of this study suggested that JTT administration suppresses skeletal muscle atrophy and motor function decline in SAMP8 mice. This effect may be associated with the increased expression levels of Sirt1 and IGF-1 by JTT.

Chronic obstructive pulmonary disease (COPD) is a systemic inflammatory disorder. It often causes weight loss, which is considered a poor prognostic factor. A Japanese herbal Kampo medicine, Hochuekkito (TJ-41), has been reported to prevent systemic inflammation and weight loss in COPD patients, but the underlying biological mechanisms remain unknown. In the present study, we investigated the role of TJ-41 in vivo using a mouse model of lung emphysema. We used lung epithelium-specific Taz conditional knockout mice (Taz CKO mice) as the lung emphysema model mimicking the chronic pulmonary inflammation in COPD. Acute inflammation was induced by intratracheal lipopolysaccharide administration, simulating COPD exacerbation. Mice were fed a diet containing 2% TJ-41 or a control diet. Taz CKO mice showed increased numbers of inflammatory cells in the bronchoalveolar lavage fluid compared to control mice. This effect was reduced by TJ-41 treatment. In the acute exacerbation model, TJ-41 mitigated the increased numbers of inflammatory cells in the bronchoalveolar lavage fluid and attenuated lung inflammation in histopathological studies. Additional in vitro expe