Structure-Based Specific Detection and Inhibition of Monoamine Oxidases and Their Applications in Central Nervous System Diseases

The involvement of the mitochondrial membrane in drug delivery

Treatment effectiveness and biosafety are critical for disease therapy. Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. To further enhance the precision of disease treatment, future research should shift focus from targeted cellular delivery to targeted subcellular delivery. As the cellular powerhouses, mitochondria play an indispensable role in cell growth and regulation and are closely involved in many diseases (e.g., cancer, cardiovascular, and neurodegenerative diseases). The double-layer membrane wrapped on the surface of mitochondria not only maintains the stability of their internal environment but also plays a crucial role in fundamental biological processes, such as energy generation, metabolite transport, and information communication. A growing body of evidence suggests that various diseases are tightly related to mitochondrial imbalance. Moreover, mitochondria-targeted strategies hold great potential to decrease therapeutic threshold dosage, minimize side effects, and promote the development of precision medicine. Herein, we introduce the structure and function of mitochondrial membranes, summarize and discuss the important role of mitochondrial membrane-targeting materials in disease diagnosis/treatment, and expound the advantages of mitochondrial membrane-assisted drug delivery for disease diagnosis, treatment, and biosafety. This review helps readers understand mitochondria-targeted therapies and promotes the application of mitochondrial membranes in drug delivery. STATEMENT OF SIGNIFICANCE: Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. Compared to cell-targeted treatment, targeting of mitochondria for drug delivery offers higher efficiency and improved biosafety and will promote the development of precision medicine. As a natural material, the mitochondrial membrane exhibits excellent biocompatibility and can serve as a carrier for mitochondria-targeted delivery. This review provides an overview of the structure and function of mitochondrial membranes and explores the potential benefits of utilizing mitochondrial membrane-assisted drug delivery for disease treatment and biosafety. The aim of this review is to enhance readers' comprehension of mitochondrial targeted therapy and to advance the utilization of mitochondrial membrane in drug delivery.

Near-Infrared Fluorescence Probe for Monoamine Oxidase A with a Large Stokes Shift for Intraoperative Navigation

Monoamine oxidase A (MAO-A) is a dimeric flavoprotein that is found in the mitochondrial membrane. Currently, there is a lack of near-infrared fluorescent probes (NIR-FPs) with good specificity and high sensitivity for detecting MAO-A, making it difficult to accurately recognize and image cells in vitro and in vivo. In this study, the NIR-FP DDM-NH2 was designed and synthesized in order to detect MAO-A specifically in live biological systems. The probe comprised two functional components: dicyanoisophosphone as an NIR dye precursor and alanine as a recognition moiety. After identifying MAO-A, the probe exhibited an NIR emission peak at 770 nm with a significant Stokes shift (180 nm), 11-fold response factor, low detection limit of 99.7 nM, and considerably higher affinity toward MAO-A than that toward MAO-B, indicating high sensitivity. In addition, DDM-NH2 was effective when applied to the image-based assessment of MAO-A activity in HeLa cells, zebrafish, and tumor-bearing mice, demonstrating great potential for visualization-based research and MAO-A application in vivo.

Ultrafast Detection of Monoamine Oxidase A in Live Cells and Clinical Glioma Tissues Using an Affinity Binding-Based Two-Photon Fluorogenic Probe

Abnormal expression of monoamine oxidase A (MAO-A) has been implicated in the development of human glioma, making MAO-A a promising target for therapy. Therefore, a rapid determination of MAO-A is critical for diagnosis. Through in silico screening of two-photon fluorophores, we discovered that a derivative of N,N-dimethyl-naphthalenamine (pre-mito) can effectively fit into the entrance of the MAO-A cavity. Substitutions on the N-pyridine not only further explore the MAO-A cavity, but also enable mitochondrial targeting ability. The aminopropyl substituted molecule, CD1, showed the fastest MAO-A detection (within 20 s), high MAO-A affinity and selectivity. It was also used for in situ imaging of MAO-A in living cells, enabling a comparison of the MAO-A content in human glioma and paracancerous tissues. Our results demonstrate that optimizing the affinity binding-based fluorogenic probes significantly improves their detection rate, providing a general approach for rapid detection probe design and optimization.

Potential biomarkers of addiction identified by real-time PCR in human peripheral blood lymphocytes: a narrative review

Addiction-related neurobiological factors could be considered as potential biomarkers. The concentration of peripheral biomarkers in tissues like blood lymphocytes may mirror their brain levels. This review is focused on the mRNA expression of potential addiction biomarkers in human peripheral blood lymphocytes (PBLs). PubMed, EMBASE, Web of Science, Scopus and Google Scholar were searched using the keywords 'addiction', 'biomarker', 'peripheral blood lymphocyte', 'gene expression' and 'real-time PCR'. The results showed the alterations in the regulation of genes such as dopamine receptors, opioid receptors, NMDA receptors, cannabinoid receptors, α-synuclein, DYN, MAO-A, FosB and orexin-A as PBLs biomarkers in addiction stages. Such variations could also be found during abstinence and relapse. PBLs biomarkers may help in drug development and have clinical implications.

Simultaneously Detecting Monoamine Oxidase A and B in Disease Cell/Tissue Samples Using Paper-Based Devices

As enzymes in the outer membrane of the mitochondrion, monoamine oxidases (MAOs) can catalyze the oxidative deamination of monoamines in the human body. According to different substrates, MAOs can be divided into MAO-A and MAO-B. The imbalance of the MAO-A is associated with neurological degeneration, while excess MAO-B activity is closely connected with Parkinson's disease (PD) and Alzheimer's disease (AD); therefore, detection of MAOs is of great significance for the diagnosis and treatment of these diseases. This work reports the multiplexed detection of MAO-A and MAO-B using paper-based devices based on chemiluminescence (CL). The detection limits were 5.01 pg/mL for MAO-A and 8.50 pg/mL for MAO-B in human serum. In addition, we used paper-based devices to detect MAOs in human cells and tissue samples and found that the results of paper-based detection and Western blotting (WB) showed the same trend. While only one antibody can be incubated on the same membrane by WB, multiple antibodies incubated on the same paper enabled simultaneous detection of MAO-A and MAO-B by paper-based devices. The paper-based assay could be used for preliminary early screening of clinical samples for MAOs and can be extended as an alternative to WB for multiplexed detection of various proteins in disease cell or tissue samples.

Similarities Between Depression and Neurodegenerative Diseases: Pathophysiology, Challenges in Diagnosis and Treatment Options

Depressive disorder and neurodegenerative diseases are two different clinical entities. Depression is a common psychiatric disorder in the general population. However, when present concomitantly with neurodegenerative disorders, its diagnosis becomes challenging. In many cases, patients remain undiagnosed and hence, untreated, worsening the prognosis of the neurodegenerative diseases and impairing the quality of life. One of the possible reasons for the difficulties in diagnosis in such cases is that both conditions affect the central nervous system, so there might be an overlap of symptoms leading to a missed diagnosis of depression in a neurodegenerative disease patient and vice versa. Symptoms such as irritability, apathy, and decreased cognition are common to both types of disorders. Some neurodegenerative diseases, especially Alzheimer's disease, can initially present as a depressive prodrome. This may cause a difficulty in differentiating between these two conditions and a diagnosis of either conditions may be missed; hence an opportunity for timely intervention and improved outcomes is missed. An approach towards analyzing and comparing the pathological mechanisms common to both disease types will create a better understanding of depression and neurodegenerative diseases, identify their similarities, and develop improved clinical criteria to help clinicians make a timely diagnosis of these conditions present together. In the present review, various studies related to common pathological links, concomitant diagnosis challenges, and ongoing research about different treatment options are discussed.

Tranylcypromine specificity for monoamine oxidase is limited by promiscuous protein labelling and lysosomal trapping

Monoamine oxidases MAOA and MAOB catalyze important cellular functions such as the deamination of neurotransmitters. Correspondingly, MAO inhibitors are used for the treatment of severe neuropsychiatric disorders such as depression. A commonly prescribed drug against refractory depression is tranylcypromine, however, the side effects are poorly understood. In order to decipher putative off-targets, we synthesized two tranylcypromine probes equipped with either an alkyne moiety or an alkyne-diazirine minimal photocrosslinker for in situ proteome profiling. Surprisingly, LC–MS/MS analysis revealed low enrichment of MAOA and relatively promiscuous labeling of proteins. Photoprobe labeling paired with fluorescent imaging studies revealed lysosomal trapping which could be largely reverted by the addition of lysosomotropic drugs.

Chemical proteomics and cellular imaging reveal lysosomal trapping of tranylcypromine which can be largely reverted by the addition of lysosomotropic drugs.