Download B10: Functional role of eicosanoids in host

B10: Functional role of eicosanoids in host-pathogen interactions
Pallu Redanna, University of Hyderabad
State of the art: Eicosanoids are oxygenated metabolites of eicosapolyenoic acids formed
via the lipoxygenase (LOX) and cyclooxygenase (COX) pathways. There is mounting
evidence about their role in connecting innate and adaptive immunity. Among these
prostanoids, PGE2 modulates immune and inflammatory responses (1, 2). Similarly
leukotrienes, contribute directly to airway inflammation (3). While COX-2 and 5-LOX
pathways lead to the formation of pro-inflammatory eicosanoids, the 12/15-LOX pathway has
been implicated in the biosynthesis of anti-inflammatory resolvins (4). By acting on various
immune and inflammatory reactions, these lipid mediators emerge as key regulators of the
crosstalk between innate and adaptive immunity (5). Susceptibility of individuals towards
infection depends on the level and type of eicosanoids formed in response to pathogen
infection. This in turn depends on the level of expression and functional consequences of
genetic polymorphism of the enzymes involved in eicosanoid biosynthesis.
Previous work: We have worked on eicosanoids for 25 years, specifically on the purification
and characterization of COXs and LOXs and their role in physiological and pathological
processes. Specific eicosanoids and the enzymes involved in mediating these responses
were identified. Many natural and synthetic compounds inhibiting COX-2 and/or 5-LOX have
been identified and their anti-inflammatory and anti-cancer properties were evaluated in vitro
and in vivo. Studies are also being conducted on in silico design, synthesis and biological
evaluation of selective inhibitors of COX-2 and 5-LOX, besides structural and functional
correlation studies on LOXs and COXs.
Working hypothesis and work plan: A complex network of pro- and anti-inflammatory
eicosanoids regulate intensity of inflammation during infection (6). We propose that the
extent of the inflammatory defence reaction and severity of an infectious disease may be
related to the expression level and the catalytic activity of COX-2, 5-LOX (pro-inflammatory
players) and 12/15-LOX (anti-inflammatory player). In addition SNP-related alterations in
expression levels and/or SNP-dependent loss or gain in catalytic activity are likely to impact
the effectiveness of innate host defence and thus, severity of the disease. We aim to analyze
the expression of the COX-2, 5-LOX and 12/15-LOX at gene and protein levels in blood
samples from clinically well characterized patient (infectious lung diseases) cohorts. Levels
of eicosanoid metabolites will be measured in the lung lavage fluids of these patients. We will
study SNPs in the coding and non-coding regions of 5-LOX, COX-2 and 12/15-LOX. The
functional relevance of non-synonymous SNPs, observed in the Indian population, will be
evaluated by site directed mutagenesis at Dr. Kühn’s lab (B3). The regulatory role of other
SNPs in the non-coding region and synonymous SNPs on translational activity of the mRNAs
and their stability will also be evaluated.
Proposed thesis topics: (1) Analysis of genetic polymorphisms in eicosanoid biosynthetic
enzymes and their correlation to disease manifestation; (2) Analysis of the level of proinflammatory and anti-inflammatory eicosanoids and their correlation to disease
manifestation.
Interlinkage: Our lab has been collaborating with Dr. Kühn’s lab for many years on structure
function correlation studies of 12-R- LOX and joint papers have been published (7). We will
send our student to Dr. Kühn’s lab and host his student within the scope of this project.
References: (1) Vancheri C et al (2004) The lung as a previliged site for the beneficial actions of PGE2. Trends Immunol 25:406. (2) Harris SG et al (2002). Prostaglandins as modulators of immunity. Trends Immunol 23:144-50. (3) Jame AJ et al (2007)
Human bronchial epithelial cells express an active and inducible biosynthetic pathway for leukotriene B4 and C4. Clin
Experiment.l Allergy 37:880-92 (4) Serhan CN ez al (2008) Resolving inflammation: dual anti-inflammatory and pro-resolution
lipid mediators. Nat Rev Immunol 8:349-61. (5) Harizi H et al (2004) Prostanoids and their receptors that modulate dendritic cellmediated immunity. Immunol Cell Biol 82:353-60. (6) O'Donnell VB et al (2009) Eicosanoids: generation and detection in
mammalian cells. Methods Mol Biol 462:5-23. (7) Meruvu S,…, H Kühn (2005) Sequence determinants for reaction specificity of
the murine 12(R)-Lipoxygenase: Targeted substrate modification and Site directed mutagenesis. J Biol Chem 280:36633-41.