In addition to their physiological roles, these peptides and their derivatives have been proposed as future antimicrobial therapeutics, relatively unaffected by the development of sustained microbial resistance. Although initially characterised as directly microbicidal agents, it is now clear that many CHDP also have multiple functions as modulators of inflammation and immunity, with emerging roles in diseases affecting multiple organs including the lung, skin and gastrointestinal tract. Human clinical trials using analogues of CHDP modified to maximise direct microbicidal function have achieved only moderate efficacy, perhaps due to failure to recognise the importance of the immunomodulatory functions of the native peptides. Interestingly, studies using non-microbicidal analogues of naturally-occurring CHDP that retained other bioactive functions, have demonstrated effective host defence augmentation in mice. These studies raise questions about the relative roles of microbicidal and immunomodulatory properties of naturally-occurring CHDP in infections. These studies demonstrate a critical, nonredundant role for endogenous cathelicidin in host defence against lung infection and the therapeutic potential of the unmodified peptides, but the mechanisms by which pulmonary host defence is enhanced in vivo remains unclear. Although generally presented as being primarily a consequence of direct microbicidal activity, this is not fully consistent with in vivo concentrations and microbicidal properties in a physiological environment. However, the extent to which any of the plethora of immunomodulatory properties ascribed to cathelicidins play a significant role during infection has never been demonstrated in vivo. Understanding the critical modulatory roles of native CHDP and how these contribute to innate host defence against infection, may prove to be vital in development of specific pathogen-targeted analogues of these peptides for therapeutic use. Respiratory diseases are among the most common causes of morbidity and account for 1 in 5 deaths in the UK. A third of mortalities are due to acute respiratory infections, influenza or pneumonia and pathogens resistant to conventional therapeutics represent an increasing clinical challenge. Pseudomonas aeruginosa is the primary cause of nosocomial pulmonary infections and pulmonary colonisation with this pathogen is considered to be responsible for the fatal deterioration of lung function in patients with cystic fibrosis. This opportunistic pathogen is difficult to treat because of its widespread resistance to multiple antibiotics, with the limited number of effective antimicrobial treatments reduced further by the emergence of carbapenem-and polymyxin-B resistant isolates. A greater understanding of the natural host defence mechanisms involved in pulmonary defence against this organism is required in order to develop novel therapeutic approaches.

In addition, LCPUFAs are important in regulating the inflammatory response through several mechanisms. One critical pathway is through the production of docosahexaenoic acid and arachidonic acid derived terminal metabolites, such as Resolvin D1 and Lipoxin A4, respectively. Current options for the parenteral and enteral delivery of LCPUFAs are unable to meet estimated fetal accretion rates; and, as a result, there is a rapid deficit of DHA and AA levels with no recovery to birth levels during the neonatal course. Of clinical significance, this early postnatal decline in systemic DHA levels is associated with the development of BPD. Animal data support this clinical observation as well as a potential role for DHA in attenuating the risk of BPD. In a neonatal murine model of hyperoxia-induced lung injury, pups exposed to hyperoxia and supplemental DHA, either by increasing the DHA content in dam milk or by direct enteral administration, demonstrated reduced lung inflammation and increased alveolarization compared to pups exposed to hyperoxia without DHA. However maintaining birth levels of LCPUFAs, in particular DHA and AA, is not achievable with the current standard of nutritional care in the neonatal intensive care unit. Thus, in lieu of directly changing dietary DHA and AA delivery, we sought to determine whether exogenous administration of the biologically active DHA and AA derived terminal metabolites, Resolvin D1 and/or Lipoxin A4, would attenuate hyperoxia-induced lung injury and if so, to define the pathways modulated by these mediators. In a well-established neonatal model of lung injury, the administration of the bioactive terminal metabolites of DHA and AA, RvD1 and LXA4 respectively, attenuated the morphologic and cellular responses to hyperoxia-induced lung injury. In parallel, there was improvement in pup growth with the combination of RvD1/LXA4, which was principally driven by LXA4. These findings support a mechanistic role for fatty acid derived terminal metabolites in ameliorating specific pathways that contribute to severe lung disease in preterm infants. In addition, these results may explain the association of low systemic levels of DHA to an increased risk of BPD observed in clinical studies. Consistent with previous studies, we found that exposure of mice to hyperoxia in the early neonatal period disrupts normal lung development as evidenced by the morphometric changes of increased septal wall thickness and arrested alveologenesis. Also, consistent with previous studies, is the induction of the host inflammatory response with hyperoxia exposure. In our study, we demonstrated an increase in the gene expression of CXCL2, the murine equivalent of IL-8, and to a lesser extent IL1b? We did find in parallel an increase in the gene expression of TIMP1 with a concomitant decrease in the expression of ELN, LOXL2, and Col1A1.

Paradoxically, iron can be highly toxic when allowed to accumulate in excess. Indeed, high concentrations of iron have the potential to produce toxic hydroxyl radicals through the Fenton reaction. These two facets of iron properties require that organisms must sense their internal iron load and respond appropriately by regulating iron acquisition, thereby keeping iron concentrations under tight control. Studies using the yeast model Schizosaccharomyces pombe have allowed discovery of genes encoding proteins that function in the regulation of iron homeostasis. The GATA-type transcription factor Fep1 represses several genes involved in iron acquisition when iron levels are high. A second iron-responsive factor, denoted Php4, is critical for down-regulating genes encoding ironusing proteins when iron levels are low. Php4 is a subunit of the CCAAT-binding protein complex. In response to iron starvation, Php4 is synthesized and interacts with the Php2/ Php3/Php5 heterotrimer to repress genes that encode components of iron-requiring metabolic pathways, such as the tricarboxylic acid cycle, the electron transport chain, and the iron-sulfur cluster biogenesis machinery. CGFS-type monothiol glutaredoxins are classified into two groups. The first group is composed of single-domain CGFS monothiol glutaredoxins involved in iron-sulfur protein biogenesis and maturation. The second group consists of multidomain CGFS monothiol glutaredoxins. These glutaredoxins deliver and transfer iron-sulfur clusters to proteins and subcellular compartments. In addition, they sense and communicate cellular iron status to iron-responsive transcription factors. Recent studies have suggested that the TRX domain serves as a docking site for interacting partners of multidomain CGFS monothiol glutaredoxins. The GRX domain of Grx4 contains a typical 172CGFS175 active site motif. The CGFS-type monothiol glutaredoxins can form -bridged homodimers. The combination of two GRX domains generates two Cys ligands to which a cluster can be coordinated with the aid of two glutathione molecules that provide the other two cluster ligands. This complex results in a glutathione-ligated center that is held within the monothiol glutaredoxin dimer. Inactivation of the grx4+ gene makes a constitutively active Fep1 that binds to its target gene promoters in vivo. In the absence of Grx4, Fep1 behaves like an insensitive protein, constitutively repressing target gene expression. Although the molecular basis by which Grx4 communicates iron deficiency to Fep1 remains obscure, twohybrid and coimmunoprecipitation experiments have revealed that the TRX domain of Grx4 associates strongly and constitutively with the C-terminal region of Fep1. Subsequent analyses have shown that, under low but not high iron conditions, the GRX domain of Grx4 associates with the N-terminal region of Fep1, which contains its DNA-binding domain.

Differences may concern the SL receptor itself, since only D14-like sequences have been found in the moss genome. A study of a knock-out mutant for the CCD8 gene, established that SLs regulate P. patens protonema branching, and control plant size as quorum-sensing like molecules very likely by controlling caulonema radial extension. However, a better understanding of how SLs inhibit protonema extension in moss is needed, and the cellular effects of SLs have yet to be described, particularly whether SLs inhibit cell division and/ or cell elongation. The feedback control on SL synthesis genes, previously characterized in vascular plants, has also been highlighted in moss because PpCCD7 transcripts are upregulated in the SL-deficient Ppccd8 mutant and SL application decreased PpCCD7 transcript levels. Exploring the links between the chemical structure of SL molecules and their activity on moss filament cells is useful for determining structural requirements for bioactivity. Comparison of those requirements with regard to hormonal bioactivity in vascular plants and non-vascular plants and with regard to other functions of SL in the rhizosphere may give indications on SL reception in the different systems. To date the SL-receptor has been identified only for the hormonal function in vascular plants. Structure-activity relationship studies have already been performed for the main known functions of SLs in vascular plants. Various natural SLs or synthetic analogs have been tested for their activity as a plant hormone or as a stimulant of parasitic plant seed germination or AM hyphal branching. For all SL functions, the D ring is essential for bioactivity. Although modifications of the tricyclic lactone have no major effect on pea branching, the ABC ring is essential for AM hyphal branching. In pea, some analogs are very active on pea buds but are poorly recognized by parasitic plant seeds, opening the possibility for the use of SLs in agronomy. Natural SLs found in moss and SL analogs with modified ABC rings or D ring with strong bioactivity for the control of shoot branching but not for AM hyphal branching have been tested on moss. We investigated the cellular effects of SLs on moss in the light and in the dark. Dark-grown moss filaments show negative gravitropism. Since only caulonema filaments grow in dark, caulonema length and caulonema cell sizes can be easily quantified in dark culture conditions. In addition, the use of the SL-deficient Ppccd8 mutant make it possible to better characterize the effect of exogenous SL added to the growth medium, since this effect is enhanced in comparison with the wild type which contains endogenous SLs, and as observed in other SAR studies on vascular plants. Here, we show that SLs control filament extension by decreasing the caulonema cell division rate with a slight effect on cell elongation.

Quinpirole and ropinirole, in distinct functional phases of ACD operant-drinking behaviour. D2 receptors have both and post-synaptic localization: quinpirole, at low doses, has been reported to preferentially bind to D2 autoreceptors. Ropinirole, a post-synaptic D2 agonist, is already used to restore dopaminergic tone in Parkinson’s Disease, as well as in the normalisation of the behavioural responses to natural rewards in anhedonic states. The effectiveness of these two different D2 receptors agonists in reducing drug seeking and drug taking, during extinction and relapse in ACD-induced operant behaviour, can imply important translational consequences concerning the pharmacological treatments of alcohol addiction. The aim of the present study was to investigate the neuropharmacological basis underpinning discrete aspects of operant drinking behaviour for ACD in male rats. Previous self-administration studies demonstrated that ACD possesses its own reinforcing and motivational properties since it is able to induce and maintain an operant behaviour in rats and promotes different drug-related behaviours, such as resilience to extinction, induction to relapse and to compulsive-like behaviour. Recent works by Karahanian and colleagues elegantly demonstrated that ACD has a crucial role in mediating ethanol reinforcement in the VTA. Indeed, reducing ACD generation, or increasing its metabolism in the VTA, can lead to a marked reduction of ethanol intake in naive rats, but the increase in ACD metabolism in VTA failed to affect ethanol intake in animals that consumed ethanol chronically for 2-3 months. In this regard, a role for high ACD peripheral levels, able to cross the blood-brain barrier, cannot be ruled out. Since chronic ethanol exposure leads to CYP2E1 induction and decreased activity of aldehyde dehydrogenase, it is worth exploring the pharmacological potential properties of peripheral ACD, which may also account for its positive reinforcing effects. Remarkably, some of the behavioural features of orally self-administered ACD are sensitive to the pharmacological modulation of the cannabinoid CB1 receptor, as well as of the opioid neurotransmission. These systems are largely involved in the induction of alcohol drinking behaviour and relapse and can likely influence ACD drinking behaviour through the modulation of the DAergic reward pathway, thus causing DA release in the nucleus accumbens. In the current experiments, the induction of ACD drinking behaviour was acquired along 30 days. Our data show that in the last period of training, rats’ ACD intake was significantly higher than in the previous weeks suggesting that the incentive motivation for the substance had also been increasing along time. Operant conditioning is a behavioural paradigm specifically tailored to reflect the measure of the reinforcing properties of self-administered drugs.