"The groundwork of all happiness is health." - Leigh Hunt

An in-depth study of fungal infections in living host tissues suggests that proline metabolism facilitates virulence.

An international team of scientists led by researchers from Stockholm University's Department of Molecular Biosciences, The Wiener-Grein Institute, Science Life Lab, has imaged the dynamics of fungal infection in the primary successful application of 2-photon intravital microscopy (IVM). Has decayed. Kidney of a living host. Studies show that opportunistic human fungal pathogens Enhancement of viral infection requires the power to metabolize the host-derived amino acid proline.

Recently listed as considered one of the 4 “high priority” fungal pathogens by the World Health Organization (WHO). One of its defining characteristics is that it's a commensal organism that thrives in symbiosis with other components of the human microflora, and is usually well tolerated. However, when humans experience health challenges that negatively affect the immune system, they could cause bloodstream infections which are fatal unless treated aggressively. During infection, cells are known to vary from ovoid yeast-like forms to elongated filamentous hyphal cells, a process that's related to the power of this fungus to grow as a pathogen. Although proline has long been known to stimulate hyphal growth, we now have recently discovered that proline may be used as a very important energy source. Proline breakdown occurs within the mitochondria, the powerhouse of the cell.

The research team now reports that proline is a very important energy source in other pathogenic Candida species, including multidrug-resistant, an emerging health threat and a WHO priority fungal pathogen. Dr. FitzGerald S. Silau, lead creator of the study, explains: “In fungal cells with mitochondria equipped with a full complement of energy-storing respiratory complexes, proline catabolism produces almost as much chemical energy (ATP) as is as much as catabolism. the energy-rich sugar glucose.”

Collaborating groups provided access to many models of infection, including artificial skin, co-culture with immune cells, survival in whole human blood and two model host systems. The results consistently showed that strains unable to metabolize proline exhibit significantly reduced virulence properties and a markedly reduced ability to undergo morphological transitions. These observations provide latest insights implicating proline metabolism as a key determinant of pathogenic fungal growth. Proline, considered one of the 20 naturally occurring amino acids within the body, is enriched in extracellular matrix proteins, for instance, collagen, and is thus available when connective tissue breaks down at sites of infection. is, or when the host becomes weak. As a results of the event of cancer or on the onset of sarcopenia. Intriguingly, genetic manipulation of the proline utilization (PUT) pathway and control mechanisms controlling proline utilization led to the invention that proline is toxic to cells unable to metabolize it. This latter finding was unexpected and further work is required to resolve the mystery and underlying mechanisms of its toxicity.

The kidney is the first organ affected during a bloodstream infection, and it will be important to grasp the cause. To get answers, the team initially applied a mouse model of infection, which stays invaluable for one of these work, and located that cells lacking the power to make use of proline were less invasive. They were fierce and dangerous. Specifically, mice infected with fungal cells which are unable to metabolize proline, for instance, cells that lack the Put2 enzyme (1-pyrroline-5-carboxylate (P5C) dehydrogenase), develop mild disease. or don't show symptoms. Next, state-of-the-art 2-photon intravital microscopy (IVM) was used to visualise, in real time, the invasion of cells deep into the renal cortex inside a living host. In contrast to native wild-type cells, Put2-deficient cells (put2-/-) did not form hyphae within the kidneys. It ought to be recognized that imaging the early stages of an ongoing infection could be very difficult as a result of many aspects, resembling the small size and scarcity of fungal cells and the constant movements related to vital and life-sustaining processes in living hosts.

“The use of engineered reporter strains and differential staining techniques enabled us to rapidly detect fungal growth deep within tissue. IVM is truly a game-changer because it allows us to capture dynamic processes in organs in their intact physiological context and at depth. allows imaging with conventional fluorescence or confocal microscopy,” says Dr. Christian Pickert, head of the Intravital Microscopy Facility-Stockholm University (IVMSU) and co-author of the paper.

As the study's senior creator Professor Per O'Ljungdahl explains: “The kidney is a major center of proline metabolism, which aligns our data with known processes associated with kidney function and makes this work even more interesting. Our future We will also extend the application of IVM to other Candida species to directly assess proline utilization in the kidney and develop sets of reporter strains. A proline metabolic network adapted to the host environment is a common and key feature of important opportunistic human fungal pathogens of increasing concern to human health.”