Emerging Target-Directed Approaches for the Treatment and Diagnosis of Microbial Infections

With the rising levels of drug resistance, developing efficient antimicrobial therapies has become a priority. A promising strategy is the conjugation of antibiotics with relevant moieties that can potentiate their activity by target-directing. The conjugation of siderophores with antibiotics allows them to act as Trojan horses by hijacking the microorganisms' highly developed iron transport systems and using them to carry the antibiotic into the cell. Through the analysis of relevant examples of the past decade, this Perspective aims to reveal the potential of siderophore-antibiotic Trojan horses for the treatment of infections and the role of siderophores in diagnostic techniques. Other conjugated molecules will be the subject of discussion, namely those involving vitamin B12, carbohydrates, and amino acids, as well as conjugated compounds targeting protein degradation and β-lactamase activated prodrugs.

Antioxidants in Sunscreens: Which and What For?

Ultraviolet (UV) radiation promotes the generation of reactive oxygen species (ROS) and nitrogen species (RNS), resulting in skin damage. Cosmetic industries have adopted a strategy to incorporate antioxidants in sunscreen formulations to prevent or minimize UV-induced oxidative damage, boost photoprotection effectiveness, and mitigate skin photoaging. Many antioxidants are naturally derived, mainly from terrestrial plants; however, marine organisms have been increasingly explored as a source of new potent antioxidant molecules. This work aims to characterize the frequency of the use of antioxidants in commercial sunscreens. Photoprotective formulations currently marketed in parapharmacies and pharmacies were analyzed with respect to the composition described on the label. As a result, pure compounds with antioxidant activity were found. The majority of sunscreen formulations contained antioxidants, with vitamin E and its derivatives the most frequent. A more thorough analysis of these antioxidants is also provided, unveiling the top antioxidant ingredients found in sunscreens. A critical appraisal of the scientific evidence regarding their effectiveness is also performed. In conclusion, this work provides an up-to-date overview of the use of antioxidants in commercial sunscreens for a better understanding of the advantages associated with their use in photoprotective formulations.

Autophagy (but not metabolism) is a key event in mitoxantrone-induced cytotoxicity in differentiated AC16 cardiac cells

Mitoxantrone (MTX) is an antineoplastic agent used to treat advanced breast cancer, prostate cancer, acute leukemia, lymphoma and multiple sclerosis. Although it is known to cause cumulative dose-related cardiotoxicity, the underlying mechanisms are still poorly understood. This study aims to compare the cardiotoxicity of MTX and its' pharmacologically active metabolite naphthoquinoxaline (NAPHT) in an in vitro cardiac model, human-differentiated AC16 cells, and determine the role of metabolism in the cardiotoxic effects. Concentration-dependent cytotoxicity was observed after MTX exposure, affecting mitochondrial function and lysosome uptake. On the other hand, the metabolite NAPHT only caused concentration-dependent cytotoxicity in the MTT reduction assay. When assessing the effect of different inhibitors/inducers of metabolism, it was observed that metyrapone (a cytochrome P450 inhibitor) and phenobarbital (a cytochrome P450 inducer) slightly increased MTX cytotoxicity, while 1-aminobenzotriazole (a suicide cytochrome P450 inhibitor) decreased fairly the MTX-triggered cytotoxicity in differentiated AC16 cells. When focusing in autophagy, the mTOR inhibitor rapamycin and the autophagy inhibitor 3-methyladenine exacerbated the cytotoxicity caused by MTX and NAPHT, while the autophagy blocker, chloroquine, partially reduced the cytotoxicity of MTX. In addition, we observed a decrease in p62, beclin-1, and ATG5 levels and an increase in LC3-II levels in MTX-incubated cells. In conclusion, in our in vitro model, neither metabolism nor exogenously given NAPHT are major contributors to MTX toxicity as seen by the residual influence of metabolism modulators used on the observed cytotoxicity and by NAPHT's low cytotoxicity profile. Conversely, autophagy is involved in MTX-induced cytotoxicity and MTX seems to act as an autophagy inducer, possibly through p62/LC3-II involvement.

Derivatives of Trimethoxybenzoic Acid and Gallic Acid as Potential Efflux Pump Inhibitors: In Silico and In Vitro Studies

The overexpression of efflux pumps is one of the strategies used by bacteria to resist antibiotics and could be targeted to circumvent the antibiotic crisis. In this work, a series of trimethoxybenzoic acid derivatives previously described as antifouling compounds was explored for potential antimicrobial activity and efflux pump (EP) inhibition. First, docking studies on the acridine resistance proteins A and B coupled to the outer membrane channel TolC (AcrAB-TolC) efflux system and a homology model of the quinolone resistance protein NorA EP were performed on 11 potential bioactive trimethoxybenzoic acid and gallic acid derivatives. The synthesis of one new trimethoxybenzoic acid derivative (derivative 13) was accomplished. To investigate the potential of this series of 11 derivatives as antimicrobial agents, and in reverting drug resistance, the minimum inhibitory concentration was determined on several strains (bacteria and fungi), and synergy with antibiotics and EP inhibition were investigated. Derivative 10 showed antibacterial activity against the studied strains, derivatives 5 and 6 showed the ability to inhibit EPs in the acrA gene inactivated mutant Salmonella enterica serovar Typhimurium SL1344, and 6 also inhibited EPs in Staphylococcus aureus 272123. Structure-activity relationships highlighted trimethoxybenzoic acid as important for EP inhibitory activity. Although further studies are necessary, these results show the potential of simple trimethoxybenzoic acid derivatives as a source of feasible EP inhibitors.

New Antifungal Agents with Azole Moieties

Fungal conditions affect a multitude of people worldwide, leading to increased hospitalization and mortality rates, and the need for novel antifungals is emerging with the rise of resistance and immunocompromised patients. Continuous use of azole drugs, which act by inhibiting the fungal CYP51, involved in the synthesis of ergosterol, essential to the fungal cell membrane, has enhanced the resistance and tolerance of some fungal strains to treatment, thereby limiting the arsenal of available drugs. The goal of this review is to gather literature information on new promising azole developments in clinical trials, with in vitro and in vivo results against fungal strains, and complementary assays, such as toxicity, susceptibility assays, docking studies, among others. Several molecules are reviewed as novel azole structures in clinical trials and with recent/imminent approvals, as well as other innovative molecules with promising antifungal activity. Structure-activity relationship (SAR) studies are displayed whenever possible. The azole moiety is brought over as a privileged structure, with multiple different compounds emerging with distinct pharmacophores and SAR. Particularly, 1,2,3-triazole natural product conjugates emerged in the last years, presenting promising antifungal activity and a broad spectrum against various fungi.

Antifungal Activity of a Library of Aminothioxanthones

Fungal infections are one of the main causes of mortality and morbidity worldwide and taking into account the increasing incidence of strains resistant to classical antifungal drugs, the development of new agents has become an urgent clinical need. Considering that thioxanthones are bioisosteres of xanthones with known anti-infective actions, their scaffolds were selected for this study. A small library of synthesized aminothioxanthones (1-10) was evaluated for in vitro antifungal activity against Candida albicans, Aspergillus fumigatus, and Trichophyton rubrum; for the active compounds, the spectrum was further extended to other clinically relevant pathogenic fungi. The results showed that only compounds 1, 8, and 9 exhibited inhibitory and broad-spectrum antifungal effects. Given the greater antifungal potential presented, compound 1 was the subject of further investigations to study its anti-virulence activity and in an attempt to elucidate its mechanism of action; compound 1 seems to act predominantly on the cellular membrane of C. albicans ATCC 10231, altering its structural integrity, without binding to ergosterol, while inhibiting two important virulence factors-dimorphic transition and biofilm formation-frequently associated with C. albicans pathogenicity and resistance. In conclusion, the present work proved the usefulness of thioxanthones in antifungal therapy as new models for antifungal agents.

Quantification of a Sulfated Marine-Inspired Antifouling Compound in Several Aqueous Matrices: Biodegradation Studies and Leaching Assays from Polydimethylsiloxane Coatings

The development of marine-inspired compounds as non-toxic antifouling (AF) agents has been pursued in the last years. Sulfur is the third most common element in seawater. Sulfur is present in oxygenated seawater as sulfate anion (SO₄²⁻), which is the most stable combination of sulfur in seawater, and several promising AF secondary metabolites with sulfate groups have been described. However, sulfated compounds proved to be an analytical challenge to quantify by HPLC. Taking these facts into consideration, this work presents the development and validation of a method for the quantification of gallic acid persulfate (GAP) in seawater and ultrapure water matrix, based on hydrophilic interaction liquid chromatography (HILIC). This method was used to evaluate GAP stability following several abiotic and biotic degradation assays, and to quantify its release in seawater from room-temperature-vulcanizing polydimethylsiloxane commercial coating. GAP was very stable in several water matrices, even at different pH values and in the presence/absence of marine microorganisms and presented a leaching value lower than 0.5%. This work discloses HILIC as an analytical method to overcome the difficulties in quantifying sulfated compounds in water matrices and highlights the potential of GAP as a promising long-lasting coating.

Fiscalin Derivatives as Potential Neuroprotective Agents

Neurodegenerative diseases (ND) share common molecular/cellular mechanisms that contribute to their progression and pathogenesis. In this sense, we are here proposing new neuroprotection strategies by using marine-derived compounds as fiscalins. This work aims to evaluate the protective effects of fiscalin derivatives towards 1-methyl-4-phenylpyridinium (MPP⁺)- and iron (III)-induced cytotoxicity in differentiated SH-SY5Y cells, an in vitro disease model to study ND; and on P-glycoprotein (P-gp) transport activity, an efflux pump of drugs and neurotoxins. SH-SY5Y cells were simultaneously exposed to MPP⁺ or iron (III), and noncytotoxic concentrations of 18 fiscalin derivatives (0–25 μM), being the cytotoxic effect of both MPP⁺ and iron (III) evaluated 24 and 48 h after exposure. Fiscalins 1a and 1b showed a significant protective effect against MPP⁺-induced cytotoxicity and fiscalins 1b, 2b, 4 and 5 showed a protective effect against iron (III)-induced cytotoxicity. Fiscalins 4 and 5 caused a significant P-gp inhibition, while fiscalins 1c, 2a, 2b, 6 and 11 caused a modest increase in P-gp transport activity, thus suggesting a promising source of new P-gp inhibitors and activators, respectively. The obtained results highlight fiscalins with promising neuroprotective effects and with relevance for the synthesis of new derivatives for the treatment/prevention of ND.

BDDE-Inspired Chalcone Derivatives to Fight Bacterial and Fungal Infections

The growing number of infectious diseases around the world threatens the effective response of antibiotics, contributing to the increase in antibiotic resistance seen as a global health problem. Currently, one of the main challenges in antimicrobial drug discovery is the search for new compounds that not only exhibit antimicrobial activity, but can also potentiate the antimicrobial activity and revert antibiotics’ resistance, through the interference with several mechanisms, including the inhibition of efflux pumps (EPs) and biofilm formation. Inspired by macroalgae brominated bromophenol BDDE with antimicrobial activity, a series of 18 chalcone derivatives, including seven chalcones (9–15), six dihydrochalcones (16–18, and 22–24) and five diarylpropanes (19–21, and 25 and 26), was prepared and evaluated for its antimicrobial activity and potential to fight antibiotic resistance. Among them, chalcones 13 and 14 showed promising antifungal activity against the dermatophyte clinical strain of Trichophyton rubrum, and all compounds reversed the resistance to vancomycin in Enterococcus faecalis B3/101, with 9, 14, and 24 able to cause a four-fold decrease in the MIC of vancomycin against this strain. Compounds 17–24 displayed inhibition of EPs and the formation of biofilm by S. aureus 272123, suggesting that these compounds are inhibiting the EPs responsible for the extrusion of molecules involved in biofilm-related mechanisms. Interestingly, compounds 17–24 did not show cytotoxicity in mouse embryonic fibroblast cell lines (NIH/3T3). Overall, the results obtained suggest the potential of dihydrochalcones 16–18 and 22–24, and diarylpropanes 19–21, 25 and 26, as hits for bacterial EPs inhibition, as they are effective in the inhibition of EPs, but present other features that are important in this matter, such as the lack of antibacterial activity and cytotoxicity.

Up-to-Date Overview of the Use of Natural Ingredients in Sunscreens

The photoprotective skincare segment is in high demand to meet consumer concerns on UV-induced skin damage, with a recent trend towards sunscreen alternatives with a natural origin. In this study, the use of natural ingredients, either from terrestrial or marine origin, in a panel of 444 sunscreen commercial formulations (2021) was analyzed. Ingredients from terrestrial organisms represent the large majority found in the analyzed sunscreen formulations (48%), whereas marine ingredients are present only in 13% of the analyzed products. A deeper analysis regarding the most prevalent families of ingredients from terrestrial and marine organisms used as top ingredients is also presented, as well as their mechanisms of action. This study provides an up-to-date overview of the sunscreen market regarding the use of natural ingredients, which is of relevance for scientists involved in the development of new sunscreens to identify opportunities for innovation.

UV Filters: Challenges and Prospects

The use of sunscreens is an established and recommended practice to protect skin from solar-induced damage. Around 30 UV filters can be used in sunscreen products in the European Union, which ought to follow the requirements of the regulation 1223/2009 to ensure their efficacy and safety for humans. Nevertheless, low photostability and putative toxicity for humans and environment have been reported for some UV filters. Particularly, the negative impact in marine organisms has recently raised concern on the scientific community. Therefore, it is important to develop new UV filters with improved safety profile and photostability. Over the last two decades, nearly 200 new compounds have revealed promising photoprotection properties. The explored compounds were obtained through different approaches, including exploration of natural sources, synthetic pathways, and nanotechnology. Almost 50 natural products and around 140 synthetic derivatives, such as benzimidazoles, benzotriazoles, hydroxycinnamic acids, xanthones, triazines, among others, have been studied aiming the discovery of novel, effective, and safer future photoprotective agents. Herein, we provide the reader with an overview about UV filters’ challenges and prospects, offering a forward-looking to the next-generation of UV filters.

Indole-Containing Pyrazino[2,1-b]quinazoline-3,6-diones Active against Plasmodium and Trypanosomatids

Malaria, leishmaniasis, and sleeping sickness are potentially fatal diseases that represent a real health risk for more than 3,5 billion people. New antiparasitic compounds are urgent leading to a constant search for novel scaffolds. Herein, pyrazino[2,1-b]quinazoline-3,6-diones containing indole alkaloids were explored for their antiparasitic potential against Plasmodium falciparum, Trypanosoma brucei, and Leishmania infantum. The synthetic libraries furnished promising hit compounds that are species specific (7, 12) or with broad antiparasitic activity (8). Structure-activity relationships were more evident for Plasmodium with anti-isomers (1S,4R) possessing excellent antimalarial activity, while the presence of a substituent on the anthranilic acid moiety had a negative effect on the activity. Hit compounds against malaria did not inhibit β-hematin, and in silico studies predicted these molecules as possible inhibitors for prolyl-tRNA synthetase both from Plasmodium and Leishmania. These results disclosed a potential new chemotype for further optimization toward novel and affordable antiparasitic drugs.

Multidimensional characterization of a new antifouling xanthone: Structure-activity relationship, environmental compatibility, and immobilization in marine coatings

The accumulation of marine biofouling on ship hulls causes material damage, the spread of invasive species, and, indirectly, an increase in full consumption and subsequent pollutant gas emissions. Most efficient antifouling (AF) strategies rely on the conventional release of persistent, bioaccumulative, and toxic biocides incorporated in marine coatings. A simple oxygenated xanthone, 3,4-dihydroxyxanthone (1), was previously reported as a promising AF agent toward the settlement of Mytilus galloprovincialis larvae, with a therapeutic ratio higher than the commercial biocide Econea®. In this work, a structure-AF activity relationship study, an evaluation of environmental fate, and an AF efficiency in marine coatings were performed with compound 1. Hydroxy or methoxy groups at 3 and 4 positions in compound 1 favored AF activity, and groups with higher steric hindrances were detrimental. Compound 1 demonstrated low water-solubility and a short half-life in natural seawater, contrary to Econea®. In silico environmental fate predictions showed that compound 1 does not bioaccumulate in organism tissues, in contrast to other current emerging biocides, has a moderate affinity for sediments and slow migrates to ground water. No toxicity was observed against Vibrio fischeri and Phaeodactylum tricornutum. Polyurethane-based marine coatings containing compound 1 prepared through an innovative non-release-strategy were as efficient as those containing Econea® with low releases to water after 45 days. This proof-of-concept helped to establish compound 1 as a promising eco-friendly AF agent.

Metabolites from Marine-Derived Fungi as Potential Antimicrobial Adjuvants

Marine-derived fungi constitute an interesting source of bioactive compounds, several of which exhibit antibacterial activity. These acquire special importance, considering that antimicrobial resistance is becoming more widespread. The overexpression of efflux pumps, capable of expelling antimicrobials out of bacterial cells, is one of the most worrisome mechanisms. There has been an ongoing effort to find not only new antimicrobials, but also compounds that can block resistance mechanisms which can be used in combination with approved antimicrobial drugs. In this work, a library of nineteen marine natural products, isolated from marine-derived fungi of the genera Neosartorya and Aspergillus, was evaluated for their potential as bacterial efflux pump inhibitors as well as the antimicrobial-related mechanisms, such as inhibition of biofilm formation and quorum-sensing. Docking studies were performed to predict their efflux pump action. These compounds were also tested for their cytotoxicity in mouse fibroblast cell line NIH/3T3. The results obtained suggest that the marine-derived fungal metabolites are a promising source of compounds with potential to revert antimicrobial resistance and serve as an inspiration for the synthesis of new antimicrobial drugs.

Determination of the Absolute Configuration of Bioactive Indole-Containing Pyrazino[2,1-b]quinazoline-3,6-diones and Study of Their In Vitro Metabolic Profile

In recent decades, fungi-derived naturally occurring quinazolines have emerged as potential drug candidates. Nevertheless, most studies are conducted for bioactivity assays, and little is known about their absorption, distribution, metabolism, and elimination (ADME) properties. To perform metabolic studies, the synthesis of the naturally occurring quinazolinone, fiscalin B (1), and its chloro derivative, 4-((1H-indol-3-yl)methyl)-8,10-dichloro-1-isobutyl-1,2-dihydro-6H-pyrazino[2,1-b]quinazoline-3,6(4H)-dione (2), disclosed as an antibacterial agent, was performed in a gram scale using a microwave-assisted polycondensation reaction with 22% and 17% yields, respectively. The structure of the non-natural (+)-fiscalin B was established, for the first time, by X-ray crystallography as (1R,4S)-1, and the absolute configuration of the naturally occurring fiscalin B (-)-1 was confirmed by comparison of its calculated and experimental electronic circular dichroism (ECD) spectra as (1S,4R)-1. in vitro metabolic studies were monitored for this class of natural products for the first time by ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS). The metabolic characteristics of 1 and 2 in human liver microsomes indicated hydration and hydroxylation mass changes introduced to the parent drugs.

Marine Ingredients for Sensitive Skin: Market Overview

Marine ingredients are a source of new chemical entities with biological action, which is the reason why they have gained relevance in the cosmetic industry. The facial care category is the most relevant in this industry, and within it, the sensitive skin segment occupies a prominent position. This work analyzed the use of marine ingredients in 88 facial cosmetics for sensitive skin from multinational brands, as well as their composition and the scientific evidence that supports their efficacy. Marine ingredients were used in 27% of the cosmetic products for sensitive skin and included the species Laminaria ochroleuca, Ascophyllum nodosum (brown macroalgae), Asparagopsis armata (red macroalgae), and Chlorella vulgaris (microalgae). Carotenoids, polysaccharides, and lipids are the chemical classes highlighted in these preparations. Two ingredients, namely the Ascophyllum nodosum extract and Asparagopsis armata extracts, present clinical evidence supporting their use for sensitive skin. Overall, marine ingredients used in cosmetics for sensitive skin are proposed to reduce skin inflammation and improve the barrier function. Marine-derived preparations constitute promising active ingredients for sensitive skin cosmetic products. Their in-depth study, focusing on the extracted metabolites, randomized placebo-controlled studies including volunteers with sensitive skin, and the use of extraction methods that are more profitable may provide a great opportunity for the cosmetic industry.

Structural and Drug Targeting Insights on Mutant p53

p53 is a transcription factor with a pivotal role in cell homeostasis and fate. Its impairment is a major event in tumor onset and development. In fact, about half of human cancers bear TP53 mutations that not only halt the normal function of p53, but also may acquire oncogenic gain of functions that favor tumorigenesis. Although considered undruggable for a long time, evidence has proven the capability of many compounds to restore a wild-type (wt)-like function to mutant p53 (mutp53). However, they have not reached the clinic to date. Structural studies have strongly contributed to the knowledge about p53 structure, stability, dynamics, function, and regulation. Importantly, they have afforded relevant insights into wt and mutp53 pharmacology at molecular levels, fostering the design and development of p53-targeted anticancer therapies. Herein, we provide an integrated view of mutp53 regulation, particularly focusing on mutp53 structural traits and on targeting agents capable of its reactivation, including their biological, biochemical and biophysical features. With this, we expect to pave the way for the development of improved small molecules that may advance precision cancer therapy by targeting p53.

Antimicrobial Activity of a Library of Thioxanthones and Their Potential as Efflux Pump Inhibitors

The overexpression of efflux pumps is one of the causes of multidrug resistance, which leads to the inefficacy of drugs. This plays a pivotal role in antimicrobial resistance, and the most notable pumps are the AcrAB-TolC system (AcrB belongs to the resistance-nodulation-division family) and the NorA, from the major facilitator superfamily. In bacteria, these structures can also favor virulence and adaptation mechanisms, such as quorum-sensing and the formation of biofilm. In this study, the design and synthesis of a library of thioxanthones as potential efflux pump inhibitors are described. The thioxanthone derivatives were investigated for their antibacterial activity and inhibition of efflux pumps, biofilm formation, and quorum-sensing. The compounds were also studied for their potential to interact with P-glycoprotein (P-gp, ABCB1), an efflux pump present in mammalian cells, and for their cytotoxicity in both mouse fibroblasts and human Caco-2 cells. The results concerning the real-time ethidium bromide accumulation may suggest a potential bacterial efflux pump inhibition, which has not yet been reported for thioxanthones. Moreover, in vitro studies in human cells demonstrated a lack of cytotoxicity for concentrations up to 20 µM in Caco-2 cells, with some derivatives also showing potential for P-gp modulation.

Microsequential injection analysis/lab-on-valve system for the automatic evaluation of acetylcholinesterase inhibitors

A miniaturized microsequential injection/lab-on-valve (µSIA-LOV) system was developed and shown to be a useful alternative to perform inhibitory studies on acetylcholinesterase. These studies are essential for the evaluation of the potential therapeutic effect of drugs commonly used in the treatment of Alzheimer's disease. Donepezil, galantamine, and rivastigmine were tested, in addition to compounds based on the xanthone scaffold. Four of these xanthone derivatives were identified as having EC₅₀ values between 676 and 4466 µmol/l, showing a potential inhibitory effect higher than the clinical agent rivastigmine. The developed automatic system added advantages of reduction of reagents and sample consumption (around 55 µl per analysis), lower cost per analysis, and the generation of less waste (around 1.2 ml per analysis). The µSIA-LOV system is also a robust, rapid, reliable, and simple system to use. Docking studies suggested a possible mode of interaction with the target acetylcholinesterase protein.

Tetracyclic Thioxanthene Derivatives: Studies on Fluorescence and Antitumor Activity

Thioxanthones are bioisosteres of the naturally occurring xanthones. They have been described for multiple activities, including antitumor. As such, the synthesis of a library of thioxanthones was pursued, but unexpectedly, four tetracyclic thioxanthenes with a quinazoline–chromene scaffold were obtained. These compounds were studied for their human tumor cell growth inhibition activity, in the cell lines A375-C5, MCF-7 and NCI-H460. Photophysical studies were also performed. Two of the compounds displayed GI₅₀ values below 10 µM for the three tested cell lines, and structure–activity relationship studies were established. Three compounds presented similar wavelengths of absorption and emission, characteristic of dyes with a push-pull character. The structures of two compounds were elucidated by X-ray crystallography. Two tetracyclic thioxanthenes emerged as hit compounds. One of the two compounds accumulated intracellularly as a bright fluorescent dye in the green channel, as analyzed by both fluorescence microscopy and flow cytometry, making it a promising theranostic cancer drug candidate.

Inflammation as a Possible Trigger for Mitoxantrone-Induced Cardiotoxicity: An In Vivo Study in Adult and Infant Mice

Mitoxantrone (MTX) is a pharmaceutical drug used in the treatment of several cancers and refractory multiple sclerosis (MS). Despite its therapeutic value, adverse effects may be severe, namely the frequently reported cardiotoxicity, whose mechanisms need further research. This work aimed to assess if inflammation or oxidative stress-related pathways participate in the cardiotoxicity of MTX, using the mouse as an animal model, at two different age periods (infant or adult mice) using two therapeutic relevant cumulative doses. Histopathology findings showed that MTX caused higher cardiac toxicity in adults. In MTX-treated adults, at the highest dose, noradrenaline cardiac levels decreased, whereas at the lowest cumulative dose, protein carbonylation increased and the expression of nuclear factor kappa B (NF-κB) p65 subunit and of M1 macrophage marker increased. Moreover, MTX-treated adult mice had enhanced expression of NF-κB p52 and tumour necrosis factor (TNF-α), while decreasing interleukin-6 (IL-6). Moreover, while catalase expression significantly increased in both adult and infant mice treated with the lowest MTX cumulative dose, the expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and glutathione peroxidase only significantly increased in infant animals. Nevertheless, the ratio of GAPDH to ATP synthase subunit beta decreased in adult animals. In conclusion, clinically relevant doses of MTX caused dissimilar responses in adult and infant mice, being that inflammation may be an important trigger to MTX-induced cardiotoxicity.