Human Host Defense Peptide LL-37 Stimulates Virulence Factor Production and Adaptive Resistance in Pseudomonas aeruginosa

Abstract

A multitude of different virulence factors as well as the ability to rapidly adapt to adverse environmental conditions are important features for the high pathogenicity of Pseudomonas aeruginosa. Both virulence and adaptive resistance are tightly controlled by a complex regulatory network and respond to external stimuli, such as host signals or antibiotic stress, in a highly specific manner. Here, we demonstrate that physiological concentrations of the human host defense peptide LL-37 promote virulence factor production as well as an adaptive resistance against fluoroquinolone and aminoglycoside antibiotics in P. aeruginosa PAO1. Microarray analyses of P. aeruginosa cells exposed to LL-37 revealed an upregulation of gene clusters involved in the production of quorum sensing molecules and secreted virulence factors (PQS, phenazine, hydrogen cyanide (HCN), elastase and rhamnolipids) and in lipopolysaccharide (LPS) modification as well as an induction of genes encoding multidrug efflux pumps MexCD-OprJ and MexGHI-OpmD. Accordingly, we detected significantly elevated levels of toxic metabolites and proteases in bacterial supernatants after LL-37 treatment. Pre-incubation of bacteria with LL-37 for 2 h led to a decreased susceptibility towards gentamicin and ciprofloxacin. Quantitative Realtime PCR results using a PAO1-pqsE mutant strain present evidence that the quinolone response protein and virulence regulator PqsE may be implicated in the regulation of the observed phenotype in response to LL-37. Further experiments with synthetic cationic antimicrobial peptides IDR-1018, 1037 and HHC-36 showed no induction of pqsE expression, suggesting a new role of PqsE as highly specific host stress sensor.

Local Sustained Delivery of 25-Hydroxyvitamin D3 for Production of Antimicrobial Peptides

“…Upon cleavage by proteinase 3, LL-37 is generated (38). Therefore, LL-37 can be derived from an inactive form (hCAP-18) produced in humans by various type of cells following exposure to active 1,25-hydroxyvitamin D 3 with local production critically dependent on the storage form of 25-hydroxyvitamin D 3 (39, 40). LL-37 acts as an antibiotic by disrupting the membrane of microbes exhibiting broad-spectrum microbicidal activity against bacteria, fungi, and viruses (10).…”

Sensor Kinase PA4398 Modulates Swarming Motility and Biofilm Formation in Pseudomonas aeruginosa PA14

“…As described previously (8), bacteria were harvested from the leading edges of the dendritic swarm colonies and were resuspended in RNAprotect reagent (Qiagen, Hilden, Germany). Total RNA isolation, DNase digestion, synthesis of first-strand cDNA, cDNA fragmentation, biotin labeling, and finally hybridization to Affymetrix GeneChip Pae_G1a DNA microarrays (Affymetrix UK Ltd., Freiburg, Germany) were carried out as described by Strempel et al (33). As a technical repeat, each sample was hybridized to two microarray chips.…”

The Mla pathway is critical for Pseudomonas aeruginosa resistance to outer membrane permeabilization and host innate immune clearance

“…Animals deficient in cathelicidin are hyper-susceptible to bacterial infection in multiple organs including skin [28], lung[29, 30], gut [31, 32], brain [33], kidney [34], and eye [35]. A bacterial pathogen producing significant clinical disease in the human host must maintain some level of functional resistance to endogenous AMPs including cathelicidin in order for infection to persist [36, 37]. …”