Enhancing Chemical Stability through Structural Modification of Antimicrobial Peptides with Non-Proteinogenic Amino Acids.

Multidrug-resistant bacteria (MDRB) remain a significant threat to humanity, resulting in over 1.2 million deaths per year. To combat this problem effectively, the development of therapeutic agents with diverse mechanisms of action is crucial. Antimicrobial peptides (AMPs) have emerged as promising next-generation therapeutics to combat infectious diseases, particularly MDRB. By targeting microbial membranes and inducing lysis, AMPs can effectively inhibit microbial growth, making them less susceptible to the development of resistance. Numerous structural advancements have been made to optimize the efficacy of AMPs. Previously, we developed 17KKV-Aib, a derivative of the Magainin 2 (Mag2) peptide, by incorporating a,a-disubstituted amino acids (dAAs) to modulate its secondary structure. 17KKV-Aib demonstrated potent antimicrobial activity against Gram-positive and Gram-negative bacteria, including multidrug-resistant Pseudomonas aeruginosa (MDRP), with minimal hemolytic activity against human red blood cells. However, 17KKV-Aib faces challenges regarding its susceptibility to digestive enzymes, hindering its potential as an antimicrobial agent. In this study, we designed and synthesized derivatives of 17KKV-Aib, replacing Lys residues with 4-aminopiperidine-4-carboxylic acid (Api), which is a cyclized dAA residue possessing cationic properties on its side chain. We investigated the impact of Api substitution on the secondary structure, antimicrobial activity, hemolytic activity, and resistance to digestive enzymes. Our findings revealed that introducing Api residues preserved the helical structure and antimicrobial activity and enhanced resistance to digestive enzymes, with a slight increase in hemolytic activity.

Structure-Activity Relationship Studies of Substitutions of Cationic Amino Acid Residues on Antimicrobial Peptides.

Antimicrobial peptides (AMPs) have received considerable attention as next-generation drugs for infectious diseases. Amphipathicity and the formation of a stabilized secondary structure are required to exert their antimicrobial activity by insertion into the microbial membrane, resulting in lysis of the bacteria. We previously reported the development of a novel antimicrobial peptide, 17KKV, based on the Magainin 2 sequence. The peptide was obtained by increasing the amphipathicity due to the replacement of amino acid residues. Moreover, we studied the structural development of 17KKV and revealed that the secondary structural control of 17KKV by the introduction of non-proteinogenic amino acids such as α,α-disubstituted amino acids or side-chain stapling enhanced its antimicrobial activity. Among them, peptide 1, which contains 2-aminobutyric acid residues in the 17KKV sequence, showed potent antimicrobial activity against multidrug-resistant Pseudomonus aeruginosa (MDRP) without significant hemolytic activity against human red blood cells. However, the effects of cationic amino acid substitutions on secondary structures and antimicrobial activity remain unclear. In this study, we designed and synthesized a series of peptide 1 by the replacement of Lys residues with several types of cationic amino acids and evaluated their secondary structures, antimicrobial activity, hemolytic activity, and resistance against digestive enzymes.

OIP5-AS1 Promotes Proliferation of Non-small-cell Lung Cancer and Head and Neck Squamous Cell Carcinoma Cells.

BACKGROUND/AIM: The long noncoding RNA OIP5 antisense RNA 1 (OIP5-AS1) is overexpressed in various cancer types, such as lung cancer, hepatoblastoma and cervical cancer, and functions to accelerate cell proliferation, invasion and migration. Here, we investigated the roIe of OIP5-AS1 in cell-cycle progression of H1299 and A549 non-small cell lung cancer cells, and FaDu and CAL27 head and neck squamous cell carcinoma cells. MATERIALS AND METHODS: The cells were transfected with small interfering RNA and subjected to cell-cycle analysis and reverse-transcription quantitative polymerase chain reaction (RT-qPCR). RESULTS: Silencing of OIP5-AS1 suppressed the proliferation of H1299, A549, FaDu and CAL27 cells. RT-qPCR and cell-cycle analysis revealed that silencing OIP5-AS1 increased the expression of CDK inhibitors, such as p15, p16, p18 and p19, resulting in G1-phase arrest. CONCLUSION: OIP5-AS1 regulates G1-phase progression by repressing CDK inhibitors and, thus, promotes the proliferation of H1299, A549, FaDu and CAL27 cells.

A novel compound, ferulic acid-bound resveratrol, induces the tumor suppressor gene p15 and inhibits the three-dimensional proliferation of colorectal cancer cells.

Resveratrol, a phytoalexin present in grapes and other edible foods, has been reported to have beneficial effects against various diseases including cancer. We previously reported that resveratrol and its derivative, caffeic acid-adducted resveratrol, selectively inhibit the three-dimensional (3D) proliferation of a human colorectal cancer cell line, HCT116 with activating KRAS mutation. Herein, we demonstrated that a novel compound, ferulic acid-bound resveratrol, also represses the 3D proliferation of HCT116 cells. We observed that resveratrol conjugated to two ferulic acids represses the 3D proliferation of HCT116 cells more strongly than resveratrol and resveratrol conjugated to one ferulic acid. Resveratrol conjugated to two ferulic acids also inhibited the 3D proliferation of MCF7 human breast cancer cells. We further uncovered that the resveratrol derivative increases the mRNA level of the tumor suppressor p15, a CDK inhibitor that functions as a brake of cell proliferation in HCT116 cells. These results imply that the resveratrol derivative represses 3D proliferation via increasing p15 expression in HCT116 cells.

Long Noncoding RNA, ANRIL, Regulates the Proliferation of Head and Neck Squamous Cell Carcinoma.

BACKGROUND/AIM: ANRIL is a long noncoding RNA located on INK4 locus, which encodes p15 and p16 that cause G1 phase arrest in the cell cycle. ANRIL positively regulates proliferation of several kinds of cancer cells such as lung and gastric cancers. This study, examined the effect of ANRIL in head and neck squamous cell carcinoma cells. MATERIALS AND METHODS: Cells were transfected with siRNA oligonucleotides targeting ANRIL. Transfected cells were subjected to cell-cycle and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. RESULTS: Depletion of ANRIL increased p15 mRNA in FaDu cells, and p15 and p16 mRNA in CAL27 cells and inhibited proliferation of these cells. Cell cycle analysis showed that depletion of ANRIL caused arrest at the G1 phase of the cell cycle. CONCLUSION: ANRIL promotes G1 phase progression by repressing p15 and p16, and thus promotes FaDu and CAL27 cell proliferation.