Bacterial crowd control with iron

Does structural commonality of metal complex formation by PAC-1 (anticancer), DHBNH (anti-HIV), AHL (autoinducer), and UCS1025A (anticancer) denote mechanistic similarity? Signal transduction and medical aspects

There is an urgent need of novel approaches to drugs in the cancer, HIV, and bacterial areas. Increasing resistance to conventional therapies is observed. This minireview provides novel insights for drugs in these three areas. The agents PAC-1 (anticancer), DHBNH (anti-HIV), AHL (autoinducer), and UCS1025A (anticancer) have recently attracted attention due to considerable potential based on new approaches. PAC-1 activates procaspase-3 to caspase-3, resulting in induction of apoptosis in tumor cells. DHBNH binds to a newly revealed site on HIV reverse transcriptase. The drug mainly inhibits RNase H (RNA-cleaving). AHLs comprise an important class that participates in bacterial cell communication. UCS1025A is a fungus-derived inhibitor of the enzyme telomerase, present in cancer cells, which is crucially involved in tumor cell immortality. All four agents possess chelating sites for metal binding, which has not been appreciated. In PAC-1 and DHBNH, the coordinating portion is similar to salicylaldehyde semicarbazone. For AHL and UCS1025A, the metal-binding moiety is a beta -ketoamide. Metal complexes of heavier metals are well-known electron transfer (ET) functionalities that can generate reactive oxygen species. Hence, it is reasonable to hypothesize a commonality in mechanism based on metal ET. Differences in receptor binding can result, in part, in diverse physiological responses. There is considerable literature that addresses involvement of signal transduction with the various physiologically active agents discussed herein. Thus, cell communication appears to play an important role in the biochemistry of these endogenous and exogenous substances. Details of cell signaling are presented for complexes of metals (Fe, Cu, Ni, and As), telomerase, caspase-3, and RNase. In addition, practical medical aspects are discussed.

Biofilms in nephrology

BACKGROUND

Biofilms are bacterial communities ubiquitous to moist environments. Biofilm formation is a factor in the development and persistence of infectious diseases. In clinical nephrology, biofilms influence the development of kidney stones and affect dialysis systems, including peritoneal and central venous catheters. Biofilms also play critical roles in persistent and resistant renal and urinary tract infections.

OBJECTIVE

To describe the physiology of biofilms and potential effects of biofilms upon infectious diseases, focusing on the role of biofilms in kidney stones, indwelling catheters and dialysis equipment.

METHODS

A literature search with Medline to identify pertinent English language articles published up to early 2008 using the keywords biofilm, nephrology, renal, calculi and infection.

RESULTS/CONCLUSION

Biofilms are ubiquitous in clinical nephrology and play a role in the pathogenesis of resistant infections. Strategies for reducing the effects of biofilms in nephrology are described.

Unifying mechanism for bacterial cell signalers (4,5-dihydroxy-2,3-pentanedione, lactones and oligopeptides): Electron transfer and reactive oxygen species. Practical medical features

Cell signaling has attracted much attention involving higher organisms, and more recently is of considerable interest concerning involvement in the bacterial realm. Many aspects can apply, including quorum sensing. Of the participating molecules, designated autoinducers, 4,5-dihydroxy-2,3-pentanedione (DPD) is one of the most important. It is in equilibrium with a furanone and a furanosyl-borate diester (AI-2). A prior hypothesis for cell signaling in higher organisms invoked a key role for electron transfer (ET) and reactive oxygen species (ROS), as well as conduits, relays and electrical effects. The principal ET functionalities are quinones, metal complexes, ArNO(2), and iminium species. A lesser known type is the alpha-dicarbonyl class. Diacetyl, a member, as well as its imine derivatives, can serve as a model for DPD, since the parent possesses a reduction potential amenable to ET in the biological domain. Hence, it is conceivable that DPD and its imine derivatives may be involved in ET-ROS processes. Presence of hydroxy groups should facilitate ET by DPD vs. diacetyl. Extensive prior literature supports participation of ET functionalities in action of therapeutic drugs, toxins and various illnesses. This biochemical behavior also applies to the alpha-dicarbonyl parent models. A second important bacterial autoinducer is the lactone category. Although ET functionality is lacking, the presence of the 1,3-dicarbonyl structure can provide a site for avid chelation with redox metal, e.g., iron or copper, followed by ET-ROS. Findings with added iron furnish support for the proposal. Oligopeptides comprise the third principal type of bacterial signaling agent. A prior review incorporates these within the theoretical framework based on ET by redox amino acids and redox enzymes. In recent years there has been a rapid increase in resistance to antibiotics by pathogenic bacteria. Infectious diseases are the leading cause of death worldwide and the third leading cause in the US. An alternate approach to antibiotics that are becoming less and less effective is to attenuate bacterial virulence. Bacterial infections appear to be importantly associated with biofilm formation. Since quorum sensors play a crucial role in this connection, they provide attractive targets for much-needed, novel approaches. Two of the main autoinducers investigated are the AHL and AI-2 systems. This review summarizes the literature, mostly recent, on this topic. Leads are provided by higher organisms that appear to have evolved means for disrupting bacterial cell communication and, hence, escape colonization. The main types in this category are the furanones, for which both natural and synthetic types have been investigated with promising results.

Insight into Biofilm-Associated Microbial Life

Microbes cohabit our planet and are engaged in a struggle for survival though on a microscopic scale. This endeavor allows them to develop and devise means for survival and proliferation. One such strategy is the formation of biofilms leading to establishment of a protected community. Such multi-communities may consist of harmful and pathogenic microbes, and they may cause economic problems and threats to human health. Biofilms are formed when microorganisms are typically attached to support surfaces. Biofilm-associated cells are sessile and differentiated from their suspended counterparts by generation of an extracellular polymeric substance matrix, reduced growth rates, and the up- and downregulation of specific genes. Biofilm formation is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. Development of strategies to control or prevent biofilms requires a thorough understanding of the biofilm development process. Biofilm research has witnessed exponential growth, and exciting findings have been reported. This has led us to visualize some previously un-thought-of and fascinating events. This article aims to provide an overview of biofilm research and associated challenges.