Comparison of in vitro photodynamic antimicrobial activity of protoporphyrin IX between endoscopic white light and newly developed narrowband endoscopic light against Helicobacter pylori 26695

Alkylated EDTA potentiates antibacterial photodynamic activity of protoporphyrin

Antibiotic resistance has garnered significant attention due to the scarcity of new antibiotics in development. Protoporphyrin IX (PpIX)-mediated photodynamic therapy shows promise as a novel antibacterial strategy, serving as an alternative to antibiotics. However, the poor solubility of PpIX and its tendency to aggregate greatly hinder its photodynamic efficacy. In this study, we demonstrate that alkylated EDTA derivatives (aEDTA), particularly C14-EDTA, can enhance the solubility of PpIX by facilitating its dispersion in aqueous solutions. The combination of C14-EDTA and PpIX exhibits potent antibacterial activity against Staphylococcus aureus (S. aureus) when exposed to LED light irradiation. Furthermore, this combination effectively eradicates S. aureus biofilms, which are known to be strongly resistant to antibiotics, and demonstrates high therapeutic efficacy in an animal model of infected ulcers. Mechanistic studies reveal that C14-EDTA can disrupt PpIX crystallization, increase bacterial membrane permeability and sequester divalent cations, thereby improving the accumulation of PpIX in bacteria. This, in turn, enhances reactive oxygen species (ROS) production and the antibacterial photodynamic activity. Overall, this effective strategy holds great promise in combating antibiotic-resistant strains.

Research progress in photodynamic therapy for Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a pathogenic microorganism that colonizes the human gastric mucosa and can lead to various gastric disorders, including gastritis, gastric ulcers, and gastric cancer. However, the increasing prevalence of antibiotic resistance in H. pylori has prompted the search for alternative treatment options. Photodynamic therapy has emerged as a potential alternative therapy, thus offering the advantage of avoiding some of the side effects associated with antibiotics and effectively targeting drug-resistant strains. In the postantibiotic era, photodynamic therapy (PDT) has shown promise as a novel treatment for H. pylori infection. This review focused on elucidating the mechanism of photodynamic therapy in the treatment of H. pylori. Additionally, we present an overview of the current research on photodynamic therapy by examining both standalone photodynamic therapy and combination therapies for H. pylori infection treatment. Furthermore, the safety profile of photodynamic therapy was also evaluated. Finally, we discuss the challenges and prospects associated with this innovative technology, with an aim to provide new insights and methodologies for the treatment of H. pylori infection.

Ingestible light source for intragastric antibacterial phototherapy: a device safety study on a minipig model

Helicobacter pylori gastric infections are among the most diffused worldwide, suffering from a rising rate of antibiotic resistance. In this context, some of the authors have previously designed an ingestible device in the form of a luminous capsule to perform antibacterial photodynamic inactivation in the stomach. In this study, the light-emitting capsules were tested to verify the safety of use prior to perform clinical efficacy studies. First, laboratory tests measured the capsule temperature while in function and verified its chemical resistance in conditions mimicking the gastric and gut environments. Second, safety tests in a healthy minipig model were designed and completed, to verify both the capsule integrity and the absence of side effects, associated with its illumination and transit throughout the gastrointestinal tract. To this aim, a capsule administration protocol was defined considering a total of 6 animals with n = 2 treated with 8 capsules, n = 2 treated with 16 capsules and n = 2 controls with no capsule administration. Endoscopies were performed in sedated conditions before–after every capsule administration. Biopsies were taken from the corpus and antrum regions, while the gastric cavity temperature was monitored during illumination. The bench tests confirmed a very good chemical resistance and a moderate (about 3 °C) heating of the capsules. The animal trials showed no significant effects on the gastric wall tissues, both visually and histologically, accompanied with overall good animal tolerance to the treatment. The integrity of the administered capsules was verified as well. These encouraging results pose the basis for the definition of successive trials at the clinical level.

Graphical abstract

Side effects of intra-gastric photodynamic therapy: an in vitro study

Since many years it has been acknowledged that some bacterial species, among which H. pylori, P. aeruginosa, P. acnes accumulate endogenous photosensitizers (PS) in the form of porphyrins. This makes antibacterial photodynamic therapy (PDT) easier to perform due to the possible avoidance of external PS. In this study, we focus on gastric infections associated with the presence of Helicobacter pylori (H. pylori), known to accumulate and release both protoporphyrin IX (PPIX) and coproporphyrins. PDT versus H. pylori can be carried out by modified endoscopes or by new ingestible luminous devices under development. In both cases of in vitro and in vivo applications, either for therapy (PDT) or diagnosis, scientific literature lacks studies on the possible side-effects of light treatments on the surrounding tissues. To this aim we evaluated in vitro side-effects due to a possible intrinsic photosensitivity of gastric mucosa or to a photosensitization by the PS released from the bacterium itself. Photo-toxicity studies were conducted on the AGS cell line (ATCC® CRL-1739™), commonly used as a model for the stomach mucosa tissue, considering PPIX as the photosensitizing agent. After first evaluations of PPIX dark toxicity, its uptake and accumulation sites, photo-toxicity tests were conducted using a LED light source peaked at 400 nm, by varying both PPIX concentration (50 nM - 2 μM) and light dose in the range 0.6-13 J/cm², representing different treatment procedures found in literature. The oxidative stress consequent to irradiation was investigated both in terms of ROS production and assessment of the activity of enzymes involved in ROS-related biological mechanisms. A significant phototoxic effect was found only for PPIX concentration > 100 nM for all tested light doses. This indicates that the evaluated photo-treatments do not cause side effects even with the sensitization due to PPIX released by the bacteria.

Antibacterial photosensitization through activation of coproporphyrinogen oxidase

Gram-positive bacteria cause the majority of skin and soft tissue infections (SSTIs), resulting in the most common reason for clinic visits in the United States. Recently, it was discovered that Gram-positive pathogens use a unique heme biosynthesis pathway, which implicates this pathway as a target for development of antibacterial therapies. We report here the identification of a small-molecule activator of coproporphyrinogen oxidase (CgoX) from Gram-positive bacteria, an enzyme essential for heme biosynthesis. Activation of CgoX induces accumulation of coproporphyrin III and leads to photosensitization of Gram-positive pathogens. In combination with light, CgoX activation reduces bacterial burden in murine models of SSTI. Thus, small-molecule activation of CgoX represents an effective strategy for the development of light-based antimicrobial therapies.

Photodynamic inactivation of Klebsiella pneumoniae biofilms and planktonic cells by 5-aminolevulinic acid and 5-aminolevulinic acid methyl ester

The treatment of Klebsiella pneumoniae, particularly extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae, is currently a great challenge. Photodynamic antimicrobial chemotherapy is a promising approach for killing antibiotic-resistant bacteria. The aim of this study was to evaluate the capacity of 5-aminolevulinic acid (5-ALA) and its derivative 5-ALA methyl ester (MAL) in the presence of white light to cause photodynamic inactivation (PDI) of K. pneumoniae planktonic and biofilm cells. In the presence of white light, 5-ALA and MAL inactivated planktonic cells in a concentration-dependent manner. Biofilms were also sensitive to 5-ALA and MAL-mediated PDI. The mechanisms by which 5-ALA and MAL caused PDI of ESBL-producing K. pneumonia were also investigated. Exposure of K. pneumonia to light in the presence of either 5-ALA or MAL induced cleavage of genomic DNA and the rapid release of intracellular biopolymers. Intensely denatured cytoplasmic contents and aggregated ribosomes were also detected by transmission electron microscopy. Scanning electron microscopy showed that PDI of biofilms caused aggregated bacteria to detach and that the bacterial cell envelope was damaged. This study provides insights into 5-ALA and MAL-mediated PDI of ESBL-producing K. pneumoniae.

Treatment of Helicobacter pylori infection: Current and future insights

Helicobacter pylori (H. pylori) is an important major cause of peptic ulcer disease and gastric malignancies such as mucosa-associated lymphoid tissue lymphoma and gastric adenocarcinoma worldwide. H. pylori treatment still remains a challenge, since many determinants for successful therapy are involved such as individual primary or secondary antibiotics resistance, mucosal drug concentration, patient compliance, side-effect profile and cost. While no new drug has been developed, current therapy still relies on different mixture of known antibiotics and anti-secretory agents. A standard triple therapy consisting of two antibiotics and a proton-pump inhibitor proposed as the first-line regimen. Bismuth-containing quadruple treatment, sequential treatment or a non-bismuth quadruple treatment (concomitant) are also an alternative therapy. Levofloxacin containing triple treatment are recommended as rescue treatment for infection of H. pylori after defeat of first-line therapy. The rapid acquisition of antibiotic resistance reduces the effectiveness of any regimens involving these remedies. Therefore, adding probiotic to the medications, developing anti-H. pylori photodynamic or phytomedicine therapy, and achieving a successful H. pylori vaccine may have the promising to present synergistic or additive consequence against H. pylori, because each of them exert different effects.

Synergistic in vitro photodynamic antimicrobial activity of methylene blue and chitosan against Helicobacter pylori 26695

BACKGROUND

Photodynamic therapy (PDT) is a method for killing cells (bacterial, fungal and cancer cells) or virus using photosensitizers (PS) and light of various wavelengths. In vitro PDT using endoscopic light against H. pylori was effective at a concentration of 0.2mg/mL of MB. The purpose of this study was to increase the effect of photodynamic modality against H. pylori by addition of chitosan to MB.

METHODS

The bactericidal effect was measured by counting viable cells after PDT. The degree of damage to DNA was confirmed using alkaline gel electrophoresis. Cellular DNA damage was demonstrated by ethidium bromide monoazide-quantitative polymerase chain reaction (EMA-qPCR).

RESULTS

In the groups treated with either 0.04 mg/mL MB alone or 0.02 mg/mL MB with endoscopic light for 15 min, viable cells were decreased approximately tenfold. The group treated with 0.04 mg/mL of MB with light, showed more effective bactericidal activity than 0.02 mg/mL of MB treatment. By 0.05% chitosan pre-treatment followed with 0.04 mg/mL of MB and light irradiation, viable cells were decreased 10(7)-fold. The DNA damage caused by PDT as demonstrated by alkaline gel electrophoresis was greater in the MB plus chitosan-treated group than in control and MB-treated groups. Cellular DNA damage demonstrated by EMA-qPCR was also greater in the group treated with MB plus chitosan than in the MB-treated group.

CONCLUSION

The bactericidal effects with PDT using MB were increased with the concentration of photosensitizer and chitosan treatment, peculiarly before endoscopic light irradiation.

Overview of the phytomedicine approaches against Helicobacter pylori

Helicobacter pylori (H. pylori) successfully colonizes the human stomach of the majority of the human population. This infection always causes chronic gastritis, but may evolve to serious outcomes, such as peptic ulcer, gastric carcinoma or mucosa-associated lymphoid tissue lymphoma. H. pylori first line therapy recommended by the Maastricht-4 Consensus Report comprises the use of two antibiotics and a proton-pomp inhibitor, but in some regions failure associated with this treatment is already undesirable high. Indeed, treatment failure is one of the major problems associated with H. pylori infection and is mainly associated with bacterial antibiotic resistance. In order to counteract this situation, some effort has been allocated during the last years in the investigation of therapeutic alternatives beyond antibiotics. These include vaccines, probiotics, photodynamic inactivation and phage therapy, which are briefly revisited in this review. A particular focus on phytomedicine, also described as herbal therapy and botanical therapy, which consists in the use of plant extracts for medicinal purposes, is specifically addressed, namely considering its history, category of performed studies, tested compounds, active principle and mode of action. The herbs already experienced are highly diverse and usually selected from products with a long history of employment against diseases associated with H. pylori infection from each country own folk medicine. The studies demonstrated that many phytomedicine products have an anti-H. pylori activity and gastroprotective action. Although the mechanism of action is far from being completely understood, current knowledge correlates the beneficial action of herbs with inhibition of essential H. pylori enzymes, modulation of the host immune system and with attenuation of inflammation.