Anti-inflammatory, analgesic and antioxidant activities of novel kyotorphin-nitroxide hybrid molecules

Enhancing Cardiomyocyte Resilience to Ischemia-Reperfusion Injury: The Therapeutic Potential of an Indole-Peptide-Tempo Conjugate (IPTC)

Ischemia/reperfusion (I/R) injury leads to apoptosis and extensive cellular and mitochondrial damage, triggered by the early generation and subsequent accumulation of mitochondrial reactive oxygen species (mtROS). This condition not only contributes to the pathology of I/R injury itself but is also implicated in a variety of other diseases, especially within the cardiovascular domain. Addressing mitochondrial oxidative stress thus emerges as a critical therapeutic target. In this context, our study introduces an indole-peptide-tempo conjugate (IPTC), a compound designed with dual functionalities: antioxidative properties and the ability to modulate autophagy. Our findings reveal that IPTC effectively shields H9C2 cardiomyocytes against hypoxia/reoxygenation (H/R) damage, primarily through counteracting mtROS overproduction linked to impaired mitophagy and mitochondrial dysfunction. We propose that IPTC operates by simultaneously reducing mtROS levels and inducing mitophagy, highlighting its potential as a novel therapeutic strategy for mitigating mitochondrial oxidative damage and, by extension, easing I/R injury and potentially other related cardiovascular conditions.

Recent advances in the development of active hybrid molecules in the treatment of cardiovascular diseases

Multifactorial nature of the underlying pathophysiology of chronic disorders hinders in the effective treatment and management of many complex diseases. The conventional targeted therapies have limited applications due to highly complicated disease etiology. Cardiovascular diseases (CVDs) are the group of disorders of the heart and blood vessels. Currently, there is limited knowledge on the underlying cellular and molecular mechanisms of many of the CVDs due to their complex pathophysiology and co-morbidities. Their management with conventional medications results in failure due to adverse drug reactions and clinical specificity of solo-targeting drug therapy. Therefore, it is critical to introduce an alternative strategy to treat multi-factorial diseases. In the past few years, discovery and use of multi-targeted drug therapy with hybrid molecules have shown promising results with minimal side effects, and thus considered a most effective approach. In this review article, prominent hybrid molecules combining with different active moieties are reported to synergistically and simultaneously block different pathways involved in CVDs. Here, we provide a critical evaluation and discussion on their pharmacology with mechanistic insights and the structure activity relationship. The timely information provided in this article reveals the recent trends of molecular hybridization to the scientific community interested in CVDs and help them in designing the next generation of multi-targeting drug therapeutics.

Review of Kyotorphin Research: A Mysterious Opioid Analgesic Dipeptide and Its Molecular, Physiological, and Pharmacological Characteristics

Tyrosine-arginine (kyotorphin), an opioid analgesic dipeptide, was discovered more than 40 years ago in 1979. The evidence accumulated during this period has established the physiological significance of kyotorphin as a neuromodulating peptide, and pharmacological applications. Some of the following important findings have been discussed in this review: (1) kyotorphin is unevenly distributed in the brain; it is found in high concentrations in the pain pathway, which involves the regions associated with morphine analgesia; (2) kyotorphin is subcellularly localized in the synaptosome fraction or nerve-ending particles; (3) a specific synthetase generates kyotorphin from tyrosine and arginine; (4) kyotorphin may be also processed from calpastatin by a novel calcium-activated neutral protease or calpain; (5) kyotorphin preloaded into the synaptosome is released by high K⁺ depolarization in a Ca²⁺-dependent manner; (6) kyotorphin has a specific G protein coupled receptor, which mediates the activation of phospholipase C (PLC) and inhibition of adenylyl cyclase through G_i; (7) leucine-arginine works as a specific kyotorphin receptor antagonist; 8) membrane-bound aminopeptidase or excretion through a peptide transporter, PEPT2, may contribute to the inactivation of kyotorphin; and (9) kyotorphin causes increased Met-enkephalin release from brain and spinal slices. It is also known that the opening of plasma membrane Ca²⁺ channels through a conformational coupling of the InsP₃ receptor with the transient receptor potential C1, which is downstream of the kyotorphin receptor-mediated activation of G_i and PLC, could be a potential underlying mechanism of Met-enkephalin release. Considering these findings, translational research is an exciting domain that can be explored in the future. As kyotorphin is a small molecule, we could design function-added kyotorphin derivatives. These studies would include not only the brain-permeable kyotorphin derivatives but also hybrid kyotorphin derivatives conjugated with small compounds that have additional pharmacological actions. Further, since there are reports of kyotorphin being involved in either the etiology or treatment of Alzheimer's disease, epilepsy, inflammation, and chronic pain, studies on the beneficial effects of kyotorphin derivatives should also be expected in the future.

Plants as Sources of Anti-Inflammatory Agents

Plants represent the main source of molecules for the development of new drugs, which intensifies the interest of transnational industries in searching for substances obtained from plant sources, especially since the vast majority of species have not yet been studied chemically or biologically, particularly concerning anti-inflammatory action. Anti-inflammatory drugs can interfere in the pathophysiological process of inflammation, to minimize tissue damage and provide greater comfort to the patient. Therefore, it is important to note that due to the existence of a large number of species available for research, the successful development of new naturally occurring anti-inflammatory drugs depends mainly on a multidisciplinary effort to find new molecules. Although many review articles have been published in this regard, the majority presented the subject from a limited regional perspective. Thus, the current article presents highlights from the published literature on plants as sources of anti-inflammatory agents.

Indole Alkaloid Derivative B, a Novel Bifunctional Agent That Mitigates 5-Fluorouracil-Induced Cardiotoxicity

Clinically approved therapeutics that mitigate chemotherapy-induced cardiotoxicity, a serious adverse effect of chemotherapy, are lacking. The aim of this study was to determine the putative protective capacity of a novel indole alkaloid derivative B (IADB) against 5-fluorouracil (5-FU)-induced cardiotoxicity. To assess the free-radical scavenging activities of IADB, the acetylcholine-induced relaxation assay in rat thoracic aorta was used. Further, IADB was tested in normal and cancer cell lines with assays gauging autophagy induction. We further examined whether IADB could attenuate cardiotoxicity in 5-FU-treated male ICR mice. We found that IADB could serve as a novel bifunctional agent (displaying both antioxidant and autophagy-modulating activities). Further, we demonstrated that IADB induced production of cytosolic autophagy-associated structures in both cancer and normal cell lines. We observed that IADB cytotoxicity was much lower in normal versus cancer cell lines, suggesting an enhanced potency toward cancer cells. The cardiotoxicity induced by 5-FU was significantly relieved in animals pretreated with IADB. Taken together, IADB treatment, in combination with chemotherapy, may lead to reduced cardiotoxicity, as well as the reduction of anticancer drug dosages that may further improve chemotherapeutic efficacy with decreased off-target effects. Our data suggest that the use of IADB may be therapeutically beneficial in minimizing cardiotoxicity associated with high-dose chemotherapy. On the basis of the redox status difference between normal and tumor cells, IADB selectively induces autophagic cell death, mediated by reactive oxygen species overproduction, in cancer cells. This novel mechanism could reveal novel therapeutic targets in chemotherapy-induced cardiotoxicity.

NO and HNO donors, nitrones, and nitroxides: Past, present, and future

The biological effects attributed to nitric oxide (^• NO) and nitroxyl (HNO) have been extensively studied, propelling their array of putative clinical applications beyond cardiovascular disorders toward other age-related diseases, like cancer and neurodegenerative diseases. In this context, the unique properties and reactivity of the N-O bond enabled the development of several classes of compounds with potential clinical interest, among which ^• NO and HNO donors, nitrones, and nitroxides are of particular importance. Although primarily studied for their application as cardioprotective agents and/or molecular probes for radical detection, continuous efforts have unveiled a wide range of pharmacological activities and, ultimately, therapeutic applications. These efforts are of particular significance for diseases in which oxidative stress plays a key pathogenic role, as shown by a growing volume of in vitro and in vivo preclinical data. Although in its early stages, these efforts may provide valuable guidelines for the development of new and effective N-O-based drugs for age-related disorders. In this report, we review recent advances in the chemistry of NO and HNO donors, nitrones, and nitroxides and discuss its pharmacological significance and potential therapeutic application.

Indole-TEMPO conjugates alleviate ischemia-reperfusion injury via attenuation of oxidative stress and preservation of mitochondrial function

Mitochondrial oxidative damage contributes to a wide range of pathologies including ischemia/reperfusion injury. Accordingly, protecting mitochondria from oxidative damage should possess therapeutic relevance. In the present study, we have designed and synthesized a series of novel indole-TEMPO conjugates that manifested good anti-inflammatory properties in a murine model of xylene-induced ear edema. We have demonstrated that these compounds can protect cells from simulated ischemia/reperfusion (s-I/R)-induced reactive oxygen species (ROS) overproduction and mitochondrial dysfunction. Furthermore, we have demonstrated that indole-TEMPO conjugates can attenuate organ damage induced in rodents via intestinal I/R injury. We therefore propose that the pharmacological profile and mechanism of action of these indole-TEMPO conjugates involve convergent roles, including the ability to decrease free radical production via lipid peroxidation which couples to an associated decrease in ROS-mediated activation of the inflammatory process. We further hypothesize that the protective effects of indole-TEMPO conjugates partially reside in maintaining optimal mitochondrial function.