Cardiopulmonary bypass down-regulates NOD signaling and inflammatory response in children with congenital heart disease

In the present study, we aimed to examine the impact of cardiopulmonary bypass (CPB) on expression and function of NOD1 and NOD2 in children with congenital heart disease (CHD), in an attempt to clarify whether NOD1 and NOD2 signaling is involved in the modulation of host innate immunity against postoperative infection in pediatric CHD patients. Peripheral blood samples were collected from pediatric CHD patients at five different time points: before CPB, immediately after CPB, and 1, 3, and 7 days after CPB. Real-time PCR, Western blot, and ELISA were performed to measure the expression of NOD1 and NOD2, their downstream signaling pathways, and inflammatory cytokines at various time points. Proinflammatorycytokine IL-6 and TNF-α levels in response to stimulation with either the NOD1 agonist Tri-DAP or the NOD2 agonist MDP were significantly reduced after CPB compared with those before CPB, which is consistent with a suppressed inflammatory response postoperatively. The expression of phosphorylated RIP2 and activation of the downstream signaling pathways NF-κB p65 and MAPK p38 upon Tri-DAP or MDP stimulation in PBMCs were substantially inhibited after CPB. The mRNA level of NOD1 and protein levels of NOD1 and NOD2 were also markedly decreased after CPB. Our results demonstrated that NOD-mediated signaling pathways were substantially inhibited after CPB, which correlates with the suppressed inflammatory response and may account, at least in part, for the increased risk of postoperative infection in pediatric CHD patients.

An investigation of the molecular interactions between statins and bacterial pathogens, and their combined impact on the human immune system

Statins are a class of drug that inhibits cholesterol biosynthesis, and are used to treat patients with high serum cholesterol levels. They exert this function by competitively binding to the enzyme 3-hydroxy-3-methylglutaryl-CoenzymeA reductase (HMGR), which catalyses the formation of mevalonate, a rate-limiting step in cholesterol biosynthesis. In addition, statins have what are called “pleiotropic effects”, which include the reduction of inflammation, immunomodulation, and antimicrobial effects. Statins can also improve survival of patients with sepsis and pneumonia. Cystic fibrosis (CF) is the most common recessive inherited disease in the Caucasian population, which is characterised by factors including, but not limited to, excessive lung inflammation and increased susceptibility to infection. Therefore, the overall objective of this study was to examine the effects of statins on CFassociated bacterial pathogens and the host response. In this work, the prevalence of HMGR was examined in respiratory pathogens, and several CF-associated pathogens were found to possess homologues of this enzyme. HMGR homology was analysed in Staphylococcus aureus, Burkholderia cenocepacia and Streptococcus pneumoniae, and the HMGR of B. cenocepacia was found to have significant conservation to that of Pseudomonas mevalonii, which is the most widely-characterised bacterial HMGR. However, in silico analysis revealed that, unlike S. aureus and S. pneumoniae, B. cenocepacia did not possess homologues of other mevalonate pathway proteins, and that the HMGR of B. cenocepacia appeared to be involved in an alternative metabolic pathway. The effect of simvastatin was subsequently tested on the growth and virulence of S. aureus, B. cenocepacia and S. pneumoniae. Simvastatin inhibited the growth of all 3 species in a dose-dependent manner. In addition, statin treatment also attenuated biofilm formation of all 3 species, and reduced in vitro motility of S. aureus. Interestingly, simvastatin also increased the potency of the aminoglycoside antibiotic gentamicin against B. cenocepacia. The impact of statins was subsequently tested on the predominant CF-associated pathogen Pseudomonas aeruginosa, which does not possess a HMGR homologue. Mevastatin, lovastatin and simvastatin did not influence the growth of this species. However, sub-inhibitory statin concentrations reduced the swarming motility and biofilm formation of P. aeruginosa. The influence of statins was also examined on Type 3 toxin secretion, quorum sensing and chemotaxis, and no statin effect was observed on any of these phenotypes. Statins did not appear to have a characteristic effect on the P. aeruginosa transcriptome. However, a mutant library screen revealed that the effect of statins on P. aeruginosa biofilm was mediated through the PvrR regulator and the Cup fimbrial biosynthesis genes. Furthermore, proteomic analysis demonstrated that 6 proteins were reproducibly induced by simvastatin in the P. aeruginosa swarming cells. The effect of statins on the regulation of the host-P. aeruginosa immune response was also investigated. Statin treatment increased expression of the pro-inflammatory cytokines IL-8 and CCL20 in lung epithelial cells, but did not attenuate P. aeruginosa-mediated inflammatory gene induction. In fact, simvastatin and P. aeruginosa caused a synergistic effect on CCL20 expression. The expression of the transcriptional regulators KLF2 and KLF6 was also increased by statins and P. aeruginosa, with the induction of KLF6 by simvastatin proving to be a novel effect. Interestingly, both statins and P. aeruginosa were capable of inducing alternative splicing of KLF6. P. aeruginosa was found to induce KLF6 alternative splicing by way of the type 3 secreted toxin ExoS. In addition, a mechanistic role was elucidated for KLF6 in the lung, as it was determined that statin-mediated induction of this protein was responsible for the induction of the host response genes CCL20 and iNOS. Moreover, statin treatment caused a slight increase in infection-related cytotoxicity, and increased bacterial adhesion to cells. Taken together, these data demonstrate that statins can reduce the virulence of CFassociated bacterial pathogens and alter host response effectors. Furthermore, novel statin effectors were identified in both bacterial and host cells.

Investigating the developmental and behavioral consequences of maternal immune activation on affected offspring

Maternal infection during pregnancy increases the risk of several neuropsychiatric disorders later in life, many of which have a component of dopaminergic (DA) dysfunction, including schizophrenia, autism spectrum disorders (ASD), and attention deficit hyperactivity disorder (ADHD). The majority of DA neurons are found in the adult midbrain; as such the midbrain is a key region of interest regarding these disorders. The literature is conflicting regarding the behavioral alterations following maternal immune activation (MIA) exposure, and the cellular and molecular consequences of MIA on the developing midbrain remain to be fully elucidated. Thus, this thesis aimed to establish the consequences of acute and mild MIA on offspring dopamine-related behaviors, as well as the associated cellular and molecular disturbances of MIA on offspring midbrains. We utilized a rat model of MIA using low dose (50μg/kg, I.P.) of LPS administered at different gestational ages. Our first study indicated that MIA at later gestational ages significantly increased pro-inflammatory IL-1β expression, and reduced HSD11B2 expression in the placenta, which is an important regulator of fetal development. In utero LPS exposure at later gestational ages also impaired the growth of neurons from affected offspring. This study identified key gestational stages during which MIA resulted in differential effects. We utilized these time points in subsequent studies, the next of which investigated neurobehavioral outcomes following MIA. Our results from that study showed that motor differences occurred in juvenile offspring following MIA at E16 only, and these differences were compensated for in adolescence. Then, there was a decline in motor behavior capabilities in adulthood, again only for animals exposed to MIA on E16 (and not E12). Furthermore, our results also demonstrated adolescent and adult offspring that were exposed to MIA at E12 had diminished responses to amphetamine in reward seeking behaviors. In our final study, we aimed to investigate the molecular and cellular changes following MIA which might explain these behavioral alterations. This final study showed a differential inflammatory response in fetal midbrains depending on gestational age of exposure as well as differential developmental alterations. For example, LPS exposure at E16 resulted in decreased VM neurosphere size after 7DIV and this was associated with an increased susceptibility to neurotoxic effects of pro-inflammatory cytokines for VM neurospheres and VM DA neurons treated in culture. In utero LPS exposure at E16 also reduced DA neuron count of fetal VM, measured by TH staining. However, there were no differences in DA neuron number in juvenile, adolescent, or adult offspring. Similarly, LPS exposure did not alter cell number or morphology of glial cells in the midbrains of affected offspring. In conclusion, this thesis indicated later rat pregnancy (E16) as vulnerable time for MIA to affect the development of the nigrostriatal pathway and subsequent behavioral outcomes, possibly implicating a role for MIA in increased risk for disorders associated with motor behavior, like PD. These effects may be mediated through alterations in the placenta and altered inflammatory mediators in the offspring brain. This thesis has also shown that MIA in earlier rat pregnancy (E12) results in altered mesocorticolimbic function, and in particular MIA on E12 resulted in a differential response to amphetamine in affected offspring, which may implicate a role for MIA in increasing the risk for disorders associated with this pathway, including drug tolerance and addiction.

The role of inflammatory mediators in the overactive and bladder pain syndromes

The Overactive Bladder (OAB) and Bladder Pain Syndrome (BPS) are debilitating disorders for which the pathophysiological mechanisms are poorly understood. Injury or dysfunction of the protective urothelial barrier layer, specifically the proteoglycan composition and number, has been proposed as the primary pathological characteristic of BPS. For OAB, the myogenic theory with dysfunction of the muscarinic receptors is the most reiterated hypothesis. For both over activity of the inflammatory response has been posited to play a major role in these diseases. We hypothesise that BPS and OAB are peripheral sensory disorders, with an increase in inflammatory mediators, such as cytokines and chemokines, which are capable of activating, either directly or indirectly, sensory nerve activity causing the disease. The aim of the PhD is to identify potential new therapeutic targets for the treatment of BPS and OAB. We used medium throughput quantitative gene expression analysis of 96 inflammation associated mediators to measure gene expression levels in BPS and OAB bladder biopsies and compared them to control samples. Then we created a novel animal model of disease by specific proteoglycan deglycosylation of the bladder mucosal barrier, using the bacterial enzymes Chondroitinase ABC and Heparanase III. These enzymes specifically remove the glycosaminoglycan side chains from the urothelial proteoglycan molecules. We tested role of the identified mediators in this animal model. In addition, in order to determine on which patients peripheral treatment strategies may work, we assessed the effect of local anaesthetics on patients with bladder pain. Gene expression analysis did not reveal a difference in inflammatory genes in the OAB versus control biopsies. However, several genes were upregulated in BPS versus control samples, from which two genes, FGF7 and CLL21 were correlated with patient clinical phenotypes for ICS/PI symptom and problem indices respectively. In order to determine which patients are likely to respond to treatment, we sought to characterise the bladder pain in BPS patients. Using urodynamics and local anaesthetics, we differentiated patients with peripherally mediated pain and patients with central sensitisation of their pain. Finally to determine the role of these mediators in bladder pain, we created an animal model of disease, which specifically replicates the human pathology: namely disruption in the barrier proteoglycan molecules. CCL21 led to an increase in painrelated behaviour, while FGF7 attenuated this behaviour, as measured by cystometry, spinal c-fos expression and mechanical withdrawal threshold examination. In conclusion, we have identified CCL21 and FGF7 as potential targets for the treatment of BPS. Manipulation of these ligands or their receptors may prove to be valuable previously unexploited targets for the treatment of BPS.