What Is FOXO4-DRI?
FOXO4-DRI is a synthetic D-retro-inverso peptide derived from a FOXO4 sequence and investigated in molecular and cellular biology research. It is classified as an all-D-amino-acid peptide and was developed to study the FOXO4–p53 protein interaction. FOXO4-DRI appears in the scientific literature because researchers have used it as an experimental tool for investigating cellular senescence and the molecular relationship between FOXO4 and p53. More recent structural research has further examined how FOXO4-DRI interacts with the p53 transactivation domain. Current evidence is predominantly preclinical.
Research Overview Table
Chemical and Molecular Characteristics
FOXO4-DRI is a synthetic peptide with a D-retro-inverso configuration. It contains a 46-residue sequence with D-amino-acid residues and a molecular weight of 5358 g/mol. Its molecular structure contains numerous polar and charged groups, reflected in its high hydrogen-bond donor and acceptor counts and large calculated polar surface area.
The D-amino-acid configuration is a defining structural characteristic of FOXO4-DRI and distinguishes it from conventional peptides composed of L-amino acids. PubChem also records FOXO4-DIR acetate as a separate chemical form, with a molecular weight of 6019 g/mol. The exact chemical form is therefore important when documenting the molecular characteristics of research material.
Certificates:
Mechanism of Action Under Investigation
FOXO4-DRI has been investigated in relation to the protein–protein interaction between FOXO4 and p53. Structural research has examined binding between FOXO4-DRI and the N-terminal transactivation domain of p53, with the disordered TAD2 region identified as an important interaction site. The FOXO4-derived region of FOXO4-DRI also contributes to this binding interface.
Structural studies indicate that FOXO4-DRI and the p53 transactivation domain are largely disordered when examined separately and can form a transiently folded complex upon interaction. Solution-state NMR has been used to characterize this interaction and examine the regions involved. Isothermal titration calorimetry has also been used to measure the direct binding interaction between FOXO4-DRI and p53.
Research has further examined the molecular features that influence this interaction. The contribution of different FOXO4-DRI regions remains under investigation. A 2025 structural study reported that the cationic cell-permeability region also contributes to the interaction, while phosphorylation of p53 can influence binding affinity.
These findings describe molecular interactions and structural features investigated experimentally. They do not establish a therapeutic effect or demonstrate that the same interactions occur in humans.
Scientific Research Context
FOXO4-DRI appears in the scientific literature as an experimental peptide studied in molecular and cellular research. Published research includes in vitro studies and preclinical animal studies. Most of the available evidence comes from these experimental settings, so the current evidence base remains predominantly preclinical.
FOXO4-DRI Biology and Biological Pathways
Primary Biological Function
FOXO4 is a member of the FOXO family of transcription factors. It binds DNA through its forkhead domain and regulates genes involved in cell-cycle control, apoptosis, metabolism, and cellular stress responses. Studies of the FOXO4 DNA-binding domain have also examined how it recognizes specific DNA sequences and regulates transcription.
Relevant Signaling Pathways
PI3K-AKT signaling regulates FOXO4 through phosphorylation and can promote its movement from the nucleus. Under cellular stress, JNK signaling can increase FOXO4 transcriptional activity. Phosphorylation also affects FOXO4 binding to 14-3-3 proteins, which can regulate its DNA binding and localization.
Tissue-Specific Biology
FOXO4 is expressed across multiple tissues and cell types, with expression patterns that vary by tissue. Studies have examined FOXO4 in human fibroblasts, endothelial cells, and vascular smooth muscle cells. Research also shows that FOXO4 can have different functions depending on the cell type, including regulation of genes involved in cellular and vascular processes.
Experimental Biomarkers
Researchers can assess FOXO4 biology by measuring FOXO4 expression, protein localization, phosphorylation, and transcriptional activity. Related measurements can include p21 and other genes regulated through FOXO- and p53-associated transcriptional networks. These markers help characterize FOXO4-related cellular responses without serving as direct measures of FOXO4-DRI activity.
Laboratory Investigation Methods
Researchers have used NMR spectroscopy, chemical cross-linking with mass spectrometry, analytical ultracentrifugation, fluorescence-based assays, and surface plasmon resonance to study FOXO4 structure, DNA binding, and protein interactions. X-ray crystallography has also been used to examine the FOXO4 DNA-binding domain.
Experimental Models Used in Published Research
Published FOXO4-DRI research uses cell cultures, tissue based models, and animal models. Researchers select these systems based on the biological level they need to examine. Cell cultures provide controlled conditions, tissue models retain some native structure, and animal models provide whole organism context. Each system also has limits in how closely it represents human biology.
Senescent Leydig Cell Models
Researchers have used hydrogen peroxide-induced senescent TM3 Leydig cells as an in vitro model. This system provides a controlled setting for studying senescent Leydig-cell biology. Its main limitation is that cultured cells do not reproduce the cellular interactions, tissue structure, and systemic environment of the testis.
Fibroblast and Myofibroblast Models
Published FOXO4-DRI research has used mouse and human lung fibroblasts, including TGF-β-induced myofibroblast models. These cultures provide controlled systems for studying fibroblast and myofibroblast biology. Their main limitation is that isolated cell cultures do not reproduce the extracellular matrix, multicellular interactions, or tissue environment of intact lung tissue.
Keloid Fibroblast and Organ Culture Models
Researchers have used serum-limitation-induced senescent fibroblasts from keloid and normal skin, along with keloid tissue maintained in organ culture. The fibroblast model provides an isolated cellular system, while organ culture retains more of the tissue structure. Both models remain limited by the absence of normal systemic conditions and whole body physiology.
Senescent Endothelial Cell Models
Researchers have used senescent human endothelial-cell cultures as an in vitro model in FOXO4-DRI research. This model provides a controlled system for studying endothelial-cell biology. Its main limitation is that cultured endothelial cells do not reproduce the full vascular environment, including interactions with other vascular and circulating cell types.
Mouse Models
Published FOXO4-DRI research has used naturally aged mice and disease-specific mouse models, including bleomycin-induced pulmonary fibrosis. These models provide an intact organismal setting that cell cultures cannot reproduce. Their limitations include species-specific biology and differences between experimentally induced conditions and human disease.
FOXO4-DRI Published Scientific Research
Cellular Senescence
Researchers have investigated FOXO4-DRI primarily in cellular senescence, with early studies examining the relationship between FOXO4, p53, and senescent-cell biology. Later research has examined FOXO4-DRI in other areas involving cellular senescence, including reproductive aging, pulmonary fibrosis, keloid biology, and vascular aging.
Reproductive Biology
Research has examined FOXO4-DRI in age-related reproductive biology, particularly the relationship between Leydig-cell senescence, the testicular environment, and spermatogenesis. The published work has focused on how cellular senescence in Leydig cells relates to changes in reproductive biology during aging.
Pulmonary Fibrosis and Fibroblast Biology
Researchers have investigated FOXO4-DRI in fibroblast and myofibroblast biology, with particular interest in extracellular-matrix production and pulmonary fibrosis. Separate research has examined senescence-like cancer-associated fibroblasts in radiation-induced pulmonary fibrosis and their relationship to non-small cell lung cancer biology.
Bronchopulmonary Dysplasia
FOXO4-DRI has also been investigated in hyperoxia-associated bronchopulmonary dysplasia. Researchers examined cellular senescence in developing lung tissue and investigated FOXO4-DRI within this developmental pulmonary research context. The study included human lung tissue and neonatal rat research.
Keloid Biology
Researchers have investigated FOXO4-DRI in keloid-associated cellular senescence, focusing on senescent fibroblasts, p53 Ser15 phosphorylation, apoptosis, and the relationship between these processes in keloid tissue.
Endothelial and Vascular Biology
Recent research has investigated FOXO4-DRI in endothelial-cell senescence and vascular aging. Another study examined the role of senescent pulmonary vascular cells in pulmonary hypertension and included FOXO4-DRI among the experimental approaches used to investigate senescent-cell clearance.
Molecular and Structural Research
Researchers have investigated the molecular interaction between FOXO4-DRI and the p53 transactivation domain. The structural research focused on the p53 TAD2 region and the molecular features of its interaction with FOXO4-DRI, including changes in peptide and protein structure during binding.
Limitations of Current Research
Evidence Is Predominantly Preclinical
The published FOXO4-DRI literature is predominantly preclinical. Research has used cell cultures, organ-based systems, and animal models to investigate different aspects of FOXO4-DRI biology. The available studies therefore provide experimental evidence but do not establish whether these findings apply to human biology.
Human Clinical Evidence
The FOXO4-DRI studies identified in the peer-reviewed literature do not provide controlled human clinical trial evidence. Published research has instead focused on laboratory and animal systems. Human pharmacokinetics, clinical safety, and biological responses therefore remain insufficiently characterized for FOXO4-DRI itself.
Species Differences
Most in vivo FOXO4-DRI studies have used mouse models. These findings may not fully reflect human biology because aging, cellular senescence, and tissue responses can differ between mice and humans. Further research in human systems is therefore needed to determine how closely the reported animal findings apply to human biology.
Study Design Limitations
Published studies use different cell types, experimental conditions, and disease or aging models. Some research also relies on induced senescence or experimentally induced disease states. These differences can affect how findings are interpreted across studies and may not fully reproduce the complexity of naturally occurring human conditions.
Independent Replication
The FOXO4-DRI literature covers several emerging research areas, but some areas are represented by relatively few studies. Independent replication across laboratories and experimental systems would help establish how consistently the reported observations can be reproduced.
Long-Term Evidence
Long-term evidence for FOXO4-DRI remains limited. The available research does not provide extended human follow-up, and a recent review identifies long-term toxicology, pharmacokinetic, and delivery studies as important areas for further investigation.
Analytical Documentation
HPLC can be used to assess FOXO4-DRI purity by separating the peptide from related substances. LC-MS can provide molecular-mass information to support identity testing and help characterize the peptide composition. NMR has also been used directly in FOXO4-DRI research. Published structural work used solution NMR to examine the interaction between FOXO4-DRI and the p53 transactivation domain.
A Certificate of Analysis (COA) provides batch-specific analytical information, such as identity and purity results, when those tests have been performed. These records help document the chemical characteristics of research material before laboratory use. Analytical verification is important because the identity and purity of a research material need to be established separately from its biological effects. Analytical documentation verifies product identity and quality, not biological performance.
Storage and Laboratory Handling
Store FOXO4-DRI according to the product specifications. Store the lyophilized material at 2–8°C. Keep the vial sealed and protected from conditions that could affect the material during storage.
Qualified laboratory personnel should handle the material using clean laboratory practices to reduce the risk of contamination. Keep the vial closed when not in use and use appropriate laboratory equipment and work areas. Follow the product documentation and applicable laboratory procedures for storage and handling. FOXO4-DRI is intended for laboratory research use only.
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