The anti-inflammatory drug Diclofenac retains anti-listerial activity in vivo

Diclofenac-loaded PLGA nanoparticles downregulate LasI/R quorum sensing genes in pathogenic P. aeruginosa isolates

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible polymer that can gradually and consistently release drugs in a controlled manner. In this study, diclofenac sodium-loaded PLGA nanoparticles (DS-PLGA NPs) were produced by solvent evaporation technique and characterized using SEM, DLS, and zeta potential analyses. The antibacterial and antivirulence potential of DS-PLGA NPs against P. aeruginosa strains were examined using broth microdilution, crystal violet staining, hemolysis, and twitching quantification assays. Furthermore, the expression of the quorum sensing (QS) genes, lasI and lasR in P. aeruginosa strains after treatment with 1/2 MIC of DS-PLGA NPs was assessed using real-time PCR. SEM imaging of the synthesized NPs exhibited that the NPs have a spherical structure with a size range of 60-150 nm. The zeta potential of the NPs was - 15.2 mV, while the size of the particles in the aquatic environment was in a range of 111.5-153.8 nm. The MIC of prepared NPs against various strains of P. aeruginosa ranged from 4.5 to 9 mg/mL. Moreover, exposure of bacteria to sub-MIC of DS-PLGA NPs significantly down-regulated the expression of the lasI and lasR genes to 0.51- and 0.75-fold, respectively. Further, prepared NPs efficiently reduced the biofilm formation of P. aeruginosa strains by 9-27%, compared with the controls. Besides, DS-PLGA NPs showed considerable attenuation in bacterial hemolytic activity by 32-88% and twitching motility by 0-32.3%, compared with untreated cells. Overall, the present work exhibited the anti-QS activity of DS-PLGA NPs, which could be a safe and useful approach for treating P. aeruginosa infections.

Diclofenac and Meloxicam Exhibited Anti-Virulence Activities Targeting Staphyloxanthin Production in Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a worldwide leading versatile pathogen that causes a wide range of serious infections. The emergence of antimicrobial resistance against S. aureus resulted in an urgent need to develop new antimicrobials in the new era. The methicillin-resistant S. aureus (MRSA) prevalence in hospital and community settings necessitates the discovery of novel anti-pathogenic agents. Staphyloxanthin (STX) is a key virulence factor for the survival of MRSA against host innate immunity. The current work aimed to demonstrate the anti-virulence properties of meloxicam (MXM) as compared to diclofenac (DC), which was previously reported to mitigate the virulence of multidrug-resistant Staphylococcus aureus and test their activities in STX production. A total of 80 S. aureus clinical isolates were included, wherein a qualitative and quantitative assessment of STX inhibition by diclofenac and meloxicam was performed. The quantitative gene expression of STX biosynthetic genes (crtM, crtN and sigB) and hla (coded for α-hemolysin) as a virulence gene with and without DC and MXM was conducted, followed by molecular docking analysis for further confirmation. DC and MXM potently inhibited the synthesis of STX at 47 and 59 µg/mL to reach 79.3-98% and 80.6-96.7% inhibition, respectively. Treated cells also revealed a significant downregulation of virulence genes responsible for STX synthesis, such as crtM, crtN and global transcriptional regulator sigB along with the hla gene. Furthermore, computational studies unveiled strong interactions between the CrtM binding site and DC/MXM. In conclusion, this study highlights the potential role and repurposing of DC and MXM as adjuvants to conventional antimicrobials and as an anti-virulent to combat MRSA infections.

Galleria mellonella: The Versatile Host for Drug Discovery, In Vivo Toxicity Testing and Characterising Host-Pathogen Interactions

Larvae of the greater wax moth, Galleria mellonella, are a convenient in vivo model for assessing the activity and toxicity of antimicrobial agents and for studying the immune response to pathogens and provide results similar to those from mammals. G. mellonella larvae are now widely used in academia and industry and their use can assist in the identification and evaluation of novel antimicrobial agents. Galleria larvae are inexpensive to purchase and house, easy to inoculate, generate results within 24–48 h and their use is not restricted by legal or ethical considerations. This review will highlight how Galleria larvae can be used to assess the efficacy of novel antimicrobial therapies (photodynamic therapy, phage therapy, metal-based drugs, triazole-amino acid hybrids) and for determining the in vivo toxicity of compounds (e.g., food preservatives, ionic liquids) and/or solvents (polysorbate 80). In addition, the disease development processes are associated with a variety of pathogens (e.g., Staphylococcus aureus, Listeria monocytogenes, Aspergillus fumigatus, Madurella mycotomatis) in mammals are also present in Galleria larvae thus providing a simple in vivo model for characterising disease progression. The use of Galleria larvae offers many advantages and can lead to an acceleration in the development of novel antimicrobials and may be a prerequisite to mammalian testing.

Diclofenac Resensitizes Methicillin-Resistant Staphylococcus aureus to β-Lactams and Prevents Implant Infections

Implant infections caused by methicillin-resistant Staphylococcus aureus (MRSA) can cause major complications during the perioperative period. Diclofenac, one of the most widely used nonsteroidal anti-inflammatory drugs, is often used to relieve pain and inflammation. In this study, it is found that high-dose diclofenac can inhibit the growth of MRSA, and does not easily induce drug-resistant mutations after continuous passage. However, low-doses diclofenac can resensitize bacteria to β-lactams, which help to circumvent drug resistance and improve the antibacterial efficacy of conventional antibiotics. Further, low-dose diclofenac in combination with β-lactams inhibit MRSA associated biofilm formation in implants. Transcriptomic and proteomic analyses indicate that diclofenac can reduce the expression of genes and proteins associated with β-lactam resistance: mecA, mecR, and blaZ; peptidoglycan biosynthesis: murA, murC, femA, and femB; and biofilm formation: altE and fnbP. Murine implant infection models indicate that diclofenac combined with β-lactams, can substantially alleviate MRSA infections in vivo. In addition, it is investigated that low dose diclofenac can inhibit MRSA antibiotic resistance via the mecA/blaZ pathway and related biofilms in implants. The synergistic effect of diclofenac and β-lactams might have promising applications for preventing perioperative infection, considering its multitarget effects against MRSA.

Comprehensive review on mechanism of action, resistance and evolution of antimycobacterial drugs

Tuberculosis is one of the deadliest infectious diseases existing in the world since ancient times and still possesses serious threat across the globe. Each year the number of cases increases due to high drug resistance shown by Mycobacterium tuberculosis (Mtb). Available antimycobacterial drugs have been classified as First line, Second line and Third line antibiotics depending on the time of their discoveries and their effectiveness in the treatment. These antibiotics have a broad range of targets ranging from cell wall to metabolic processes and their non-judicious and uncontrolled usage in the treatment for years has created a significant problem called multi-drug resistant (MDR) tuberculosis. In this review, we have summarized the mechanism of action of all the classified antibiotics currently in use along with the resistance mechanisms acquired by Mtb. We have focused on the new drug candidates/repurposed drugs, and drug in combinations, which are in clinical trials for either treating the MDR tuberculosis more effectively or involved in reducing the time required for the chemotherapy of drug sensitive TB. This information is not discussed very adequately on a single platform. Additionally, we have discussed the recent technologies that are being used to discover novel resistance mechanisms acquired by Mtb and for exploring novel drugs. The story of intrinsic resistance mechanisms and evolution in Mtb is far from complete. Therefore, we have also discussed intrinsic resistance mechanisms of Mtb and their evolution with time, emphasizing the hope for the development of novel antimycobacterial drugs for effective therapy of tuberculosis.

Diclofenac May Induce PIA-Independent Biofilm Formation in Staphylococcus aureus Strains

Staphylococcus aureus is a pathogen commonly resistant to antibiotics. Biofilm formation is one of the important factors related to its virulence. Non-antibiotics drugs, such as nonsteroidal anti-inflammatory agents (NSAIDs), have been studied as an alternative for treating infections by multiresistant pathogens and biofilm-associated infections. In this study, the effects of NSAID sodium diclofenac on growth inhibition and biofilm formation of S. aureus were evaluated. The minimum inhibitory concentration (MIC) of diclofenac for fifty isolates ranged from 200 to 400 μg/mL. Diclofenac sub-MICs induced biofilm in 32.3% of biofilm-negative strains in tryptic soy broth. All biofilms induced by the drug showed a PIA- (polysaccharide intercellular adhesion-) independent composition, and the scanning electron microscopy showed that the induced biofilm presented a very discrete matrix. The combination of diclofenac with rifampicin sub-MICs induced strong production of PIA-dependent biofilm in three of four strains, while combination of NSAID with NaCl induced the formation of partially polysaccharide biofilm in two strains and PIA-independent biofilm in another strain. The combination of NSAID with glucose resulted in PIA-independent biofilms in all four strains tested. The results showed that diclofenac can commonly induce biofilm production by a PIA-independent pathway. However, when this NSAID is combined with other types of inducing agents, the composition of the biofilm produced may vary.

An adverse outcome pathway for immune-mediated and allergic hepatitis: a case study with the NSAID diclofenac

Many drugs have the potential to cause drug-induced liver injury (DILI); however, underlying mechanisms are diverse. The concept of adverse outcome pathways (AOPs) has become instrumental for risk assessment of drug class effects. We report AOPs specific for immune-mediated and drug hypersensitivity/allergic hepatitis by considering genomic, histo- and clinical pathology data of mice and dogs treated with diclofenac. The findings are relevant for other NSAIDs and drugs undergoing iminoquinone and quinone reactive metabolite formation. We define reactive metabolites catalyzed by CYP monooxygenase and myeloperoxidases of neutrophils and Kupffer cells as well as acyl glucuronides produced by uridine diphosphoglucuronosyl transferase as molecular initiating events (MIE). The reactive metabolites bind to proteins and act as neo-antigen and involve antigen-presenting cells to elicit B- and T-cell responses. Given the diverse immune systems between mice and dogs, six different key events (KEs) at the cellular and up to four KEs at the organ level are defined with mechanistic plausibility for the onset and progression of liver inflammation. With mice, cellular stress response, interferon gamma-, adipocytokine- and chemokine signaling provided a rationale for the AOP of immune-mediated hepatitis. With dogs, an erroneous programming of the innate and adaptive immune response resulted in mast cell activation; their infiltration into liver parenchyma and the shift to M2-polarized Kupffer cells signify allergic hepatitis and the occurrence of granulomas of the liver. Taken together, diclofenac induces divergent immune responses among two important preclinical animal species, and the injury pattern seen among clinical cases confirms the relevance of the developed AOP for immune-mediated hepatitis.

Occurrence, interactive effects and ecological risk of diclofenac in environmental compartments and biota - a review

Diclofenac, a nonsteroidal anti-inflammatory drug has turned into a contaminant of emerging concern; hence, it was included in the previous Watch List of the EU Water Framework Directive. This review paper aims to highlight the metabolism of diclofenac at different trophic levels, its occurrence, ecological risks, and interactive effects in the water cycle and biota over the past two decades. Increased exposure to diclofenac not only raises health concerns for vultures, aquatic organisms, and higher plants but also causes serious threats to mammals. The ubiquitous nature of diclofenac in surface water (river, lake canal, estuary, and sea) is compared with drinking water, groundwater, and wastewater effluent in the environment. This comprehensive survey from previous studies suggests the fate of diclofenac in wastewater treatment plants (WWTPs) and may predict its persistence in the environment. This review offers evidence of fragmentary available data for the water environment, soil, sediment, and biota worldwide and supports the need for further data to address the risks associated with the presence of diclofenac in the environment. Finally, we suggest that the presence of diclofenac and its metabolites in the environment may represent a high risk because of their synergistic interactions with existing contaminants, leading to the development of drug-resistant strains and the formation of newly emerging pollutants.

Percentage of faecal excretion of meloxicam in the Cape vultures (Gyps corprotheres)

Asian Gyps vulture species are gradually recovering from the devastating effect of diclofenac being present in contaminated carcasses. This drug was responsible for the death of over 10 million vultures in India, Nepal and Pakistan. To prevent the extinction of vultures, meloxicam was introduced after the ban of veterinary diclofenac. Meloxicam's safety in vultures was attributed to its short elimination half-life in contrast with diclofenac. The reason for the rapid elimination of meloxicam is yet to be explained. The aim of this study was to evaluate the role of biotransformation in the elimination of meloxicam. Six Cape griffon vultures (Gyps coprotheres) were treated with 2 mg/kg meloxicam intramuscularly for faecal and plasma quantification of meloxicam concentration over time. In the plasma meloxicam was characterised by a half-life, mean residence time, clearance and volume of distribution at steady state of 0.37 ± 0.10 h, 0.90 ± 0.12 h, 0.02 ± 0.00 l/h kg and 0.02 ± 0.00 l/kg respectively (presented as geometric mean). Over the 24 h monitoring period, the total non-metabolised meloxicam in the faeces was 1.35 ± 0.71% of the total concentration in the plasma. Based on the short meloxicam elimination half-life and low cumulative concentration of total faecal meloxicam over a period in excess of 10 half-lives, this study indicates that Cape griffon vultures are efficient metaboliser of meloxicam, which is suggestive of different set of cytochrome enzymes being involved in the metabolism to that for diclofenac in this species. Identification of orthologous human CYP2C9 and CYP3A4 enzyme families in vultures will be an important further step in explaining the differences in the metabolic pathway(s) of meloxicam and diclofenac for the species.

Repurposing drugs for treatment of tuberculosis: a role for non-steroidal anti-inflammatory drugs

INTRODUCTION

The number of cases of drug-resistant Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has risen rapidly in recent years. This has led to the resurgence in repurposing existing drugs, such as non-steroidal anti-inflammatory drugs (NSAIDs), for anti-TB treatment.

SOURCES OF DATA

Evidence from novel drug screening in vitro, in vivo, pharmacokinetic/pharmacodynamics analyses and clinical trials has been used for the preparation of this systematic review of the potential of NSAIDs for use as an adjunct in new TB chemotherapies.

AREAS OF AGREEMENT

Certain NSAIDs have demonstrated inhibitory properties towards actively replicating, dormant and drug-resistant clinical isolates of M. tuberculosis cells.

AREAS OF CONTROVERSY

NSAIDs are a diverse class of drugs, which have reported off-target activities, and their endogenous antimicrobial mechanism(s) of action is still unclear.

GROWING POINTS

It is essential that clinical trials of NSAIDs continue, in order to assess their suitability for addition to the current TB treatment regimen. Repurposing molecules such as NSAIDs is a vital, low-risk strategy to combat the trend of rapidly increasing antibiotic resistance.

Advanced Therapeutic Dressings for Effective Wound Healing--A Review

Advanced therapeutic dressings that take active part in wound healing to achieve rapid and complete healing of chronic wounds is of current research interest. There is a desire for novel strategies to achieve expeditious wound healing because of the enormous financial burden worldwide. This paper reviews the current state of wound healing and wound management products, with emphasis on the demand for more advanced forms of wound therapy and some of the current challenges and driving forces behind this demand. The paper reviews information mainly from peer-reviewed literature and other publicly available sources such as the US FDA. A major focus is the treatment of chronic wounds including amputations, diabetic and leg ulcers, pressure sores, and surgical and traumatic wounds (e.g., accidents and burns) where patient immunity is low and the risk of infections and complications are high. The main dressings include medicated moist dressings, tissue-engineered substitutes, biomaterials-based biological dressings, biological and naturally derived dressings, medicated sutures, and various combinations of the above classes. Finally, the review briefly discusses possible prospects of advanced wound healing including some of the emerging physical approaches such as hyperbaric oxygen, negative pressure wound therapy and laser wound healing, in routine clinical care.

Brain infection and activation of neuronal repair mechanisms by the human pathogen Listeria monocytogenes in the lepidopteran model host Galleria mellonella

Listeria monocytogenes the causative agent of the foodborne disease listeriosis in humans often involves fatal brainstem infections leading to meningitis and meningoencephalitis. We recently established the larvae of the greater wax moth (Galleria mellonella) as a model host for the investigation of L. monocytogenes pathogenesis and as a source of peptides exhibiting anti-Listeria-activity. Here we show that G. mellonella can be used to study brain infection and its impact on larval development as well as the activation of stress responses and neuronal repair mechanisms. The infection of G. mellonella larvae with L. monocytogenes elicits a cellular immune response involving the formation of melanized cellular aggregates (nodules) containing entrapped bacteria. These form under the integument and in the brain, resembling the symptoms found in human patients. We screened the G. mellonella transcriptome with marker genes representing stress responses and neuronal repair, and identified several modulated genes including those encoding heat shock proteins, growth factors, and regulators of neuronal stress. Remarkably, we discovered that L. monocytogenes infection leads to developmental shift in larvae and also modulates the expression of genes involved in the regulation of endocrine functions. We demonstrated that L. monocytogenes pathogenesis can be prevented by treating G. mellonella larvae with signaling inhibitors such as diclofenac, arachidonic acid, and rapamycin. Our data extend the utility of G. mellonella larvae as an ideal model for the high-throughput in vivo testing of potential compounds against listeriosis.

Potential role of the cardiovascular non-antibiotic (helper compound) amlodipine in the treatment of microbial infections: scope and hope for the future

The appearance of multiresistant bacterial strains coupled with the globally ongoing problem of infectious diseases point to the imperative need for novel and affordable antimicrobial drugs. The antibacterial potential of cardiovascular non-antibiotics such as amlodipine (AML), dobutamine, lacidipine, nifedipine and oxyfedrine has been reported previously. Of these drugs, AML proved to have the most significant antibacterial activity against Gram-positive and Gram-negative bacteria. Time-kill curve studies indicate that this Ca(2+) channel blocker exhibits bactericidal activity against Listeria monocytogenes and Staphylococcus aureus. AML could protect against murine listeriosis and salmonellosis at doses ranging within its maximum recommended human or non-toxic ex vivo dose. AML acts as a 'helper compound' in synergistic combination with streptomycin against several Gram-positive and Gram-negative bacterial strains in vitro as well as in the murine salmonellosis model in vivo. The present review focuses on the possible use of cardiovascular non-antibiotics such as AML as auxiliary compound targets for synergistic combinations in infections and hypertension conditions, rationalised on the basis of the activities of the compounds.

The anti-inflammatory non-antibiotic helper compound diclofenac: an antibacterial drug target

Diclofenac sodium (Dc) was found to possess antibacterial activity against both drug-sensitive and drug-resistant clinical isolates of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Mycobacterium spp., in addition to its potent anti-inflammatory activity. The time-kill curve study indicates that this non-steroidal drug exhibits bactericidal activity against Listeria, E. coli, and M. tuberculosis. The antibacterial activity of Dc comes, in part, from its ability to inhibit the DNA synthesis of E. coli and L. monocytogenes. Dc could protect murine listeriosis, salmonellosis, and tuberculosis at doses ranged within its maximum recommended human or non-toxic ex-vivo dose. Dc possesses anti-plasmid activity and acts as a 'helper compound' in synergistic combination with streptomycin against E. coli and Mycobacterium or gentamicin against Listeria. This review focuses on the possible use of Dc, a non-antibiotic helper compound, in infections and inflammatory conditions, rationalized on the basis of the activities of the compounds.

In vitro synergistic effect of gentamicin with the anti-inflammatory agent diclofenac against Listeria monocytogenes

AIMS

A total of nine Listeria monocytogenes strains (seven serotypes) were studied to ascertain whether the non-steroidal anti-inflammatory drug diclofenac (Dc) used in combination with the conventional antilisterial antibiotic gentamicin (Gm) or ampicillin (Am) synergistically augments the efficacy of the antibiotic in vitro.

METHODS AND RESULTS

The effect of combination was evaluated by the checkerboard method to obtain a fractional inhibitory concentration (FIC) index followed by kill curves. Dc was synergistic with Gm (FIC 0.37) and there was indifference with Am (FIC 1) against L. monocytogenes ATCC 51774. The magnitude of the differences between killing by a single agent and the combination observed at 24 h was significant (P < 0.05) for Dc plus Gm but not Dc plus Am.

CONCLUSIONS

Thus, the ability of extended antibiotic therapy may be improved with the help of this synergistic drug pair in listeriosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Such findings may indicate parallel administration of anti-inflammatory and anti listeriosis drugs.

In vitro and in vivo efficacies of amlodipine against Listeria monocytogenes

Listeria monocytogenes causes suppurative gastritis in BALB/c mice. We investigated the effect of the antihypertensive drug amlodipine (Aml) on the growth of L. monocytogenes in vitro and in vivo. Aml showed noteworthy inhibitory action (minimum inhibitory concentration, MIC(90) 32 microg/ml) against Listeria strains and demonstrated cidal (minimum bactericidal concentration, MBC 64 microg/ml) activity. Aml administered orally at 2.5 microg/g in female BALB/c mice for 7 days, commencing 4 days before oral challenge (1 x 10(8) CFU/ml with L. monocytogenes ATCC 51774), significantly reduced bacterial counts in the stomach (P < 0.01), liver (P < 0.01), and spleen (P < 0.05), and decreased (P < 0.05) gastric lesions, neutrophilic infiltration, edema, vascular degeneration, and necrosis of gastric tissues. It caused the down-regulation of expression of inflammatory cytokines (IFN-gamma, IL-1 beta, and TNF-alpha) compared to drug-free control. Aml may be used in the presence of an antibiotic as adjunct therapy that boosts the host immunity against Listeria. Further, QSAR studies might contribute in manipulating it as a lead compound for the synthesis of new, more effective non-antibiotics (helper compounds), perhaps devoid of side-effects, that could be recommended as compassionate therapy for listeriosis.