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bioRxiv2022

Photodynamic therapy in colorectal cancer using photosensitizers functionalized by arene-ruthenium complexes

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers worldwide and one of the main causes of cancer deaths in the global population. First-line treatment usually includes surgical procedures followed by combination chemotherapy. Despite the improvements in CRC treatments, the mortality rate remains very high, leading consequently to conventional treatment resistance. Several therapies were enrolled to this content in a way to find the best solutions for this disease. Photodynamic therapy (PDT) using photosensitizers (PS) presents itself as an original innovative therapeutic strategy that strongly limits the undesirable side effects of conventional treatment. However, low physiological solubility and a lack of selectivity of PS towards tumor sites are the principal restrictions of their current clinical use. Indeed, drug delivery systems are currently a key issue in cancer therapy. To overcome the problem of solubility and stability of PS such as porphyrins and their derivatives, metallic assemblies based on arene-ruthenium (Ru) units have begun to attract considerable attention as PS delivery systems. The purpose of this study was to demonstrate firstly the interest in the vectorization of tetrapyridylporphin (TPyP-arene-Ru) and Zn-tetrapyridylporphin arene-ruthenium (Zn-TPyP-arene-Ru) metallacages to increase their solubility in biological media and then, consequently their anticancer efficacy in PDT. Secondly, to elucidate the anticancer mechanism as well as identify the cell death process mediated by these new vectorized PS. The results showed that the two PS-arene-Ru complexes have a strong photocytotoxic effect after photoactivation on human HCT116 and HT-29 colorectal cancer cell lines. TPyP-arene-Ru-PDT induced outstanding cytotoxicity when compared to the Zn-TPyP-arene-Ru analogue. The two complexes show no significant effect on proliferation in the dark. In addition, results demonstrated that these two PS-arene-Ru complexes-PDT induce an apoptotic process through the appearance of a sub-G1 peak, phosphatidylserines externalization, poly-ADP ribose polymerase (PARP) cleavage and DNA fragmentation. Thus, our data contribute to highlighting that the incorporation of porphyrins in Ru-based assemblies could be an efficient vectorized system to treat CRC by PDT.

cancer biology↗

bioRxiv2018

Alginate-regulating genes are identified in the clinical cystic fibrosis isolate of Pseudomonas aeruginosa PA2192

Cystic fibrosis (CF) is a genetic disorder that leads to a buildup of mucus in the lungs ideal for bacterial colonization. When Pseudomonas aeruginosa enters the CF lung, it undergoes a conversion from nonmucoid to mucoid; colonization by a mucoid strain of P. aeruginosa greatly increases mortality. The mucoid phenotype is due to the production of alginate. The regulator of alginate production is the AlgT/U sigma factor. The observed phenotypic conversion is due to a mutation in the mucA gene coding for an anti-sigma factor, MucA, which sequesters AlgT/U. This mucoid phenotype is unstable when the strains are removed from the lung as they acquire second-site mutations. This in vitro reversion phenomenon is utilized to identify novel genes regulating alginate production. Previously, second-site mutations were mapped to algT/U, algO, and mucP, demonstrating their role in alginate regulation. Most of these studies were performed using a non-CF isolate. It was hypothesized that second site mutations in a clinical strain would be mapped to the same genes. In this study, a clinical, hyper-mucoid P. aeruginosa strain PA2192 was used to study the reversion phenomenon. This study found that PA2192 has a novel mucA mutation which was named them mucA180 allele. Twelve colonies were sub-cultured for two weeks without aeration at room temperature in order to obtain nonmucoid suppressors of alginate production (sap). Only 41 sap mutants were stable for more than 48 hours -- a reversion frequency of 3.9% as compared to ~90% in laboratory strains showing that PA2192 has a stable mucoid phenotype. This phenotype was restored in 28 of the 41 sap mutants when complemented with plasmids harboring algT/U. Four of the sap mutants are complemented by algO. Sequence analyses of the algT/U mutants have found no mutations in the coding region or promoter leading to the hypothesis that there is another, as yet unidentified mechanism of alginate regulation in this clinical strain.

microbiology↗