In vitro and in vivo evidence for an inflammatory role of the calcium channel TRPV4 in lung epithelium: Potential involvement in cystic fibrosis.

Cystic fibrosis (CF) is an inherited disease associated with chronic severe lung inflammation, leading to premature death. To develop innovative anti-inflammatory treatments, we need to characterize new cellular and molecular components contributing to the mechanisms of lung inflammation. Here, we focused on the potential role of "transient receptor potential vanilloid-4" (TRPV4), a nonselective calcium channel. We used both in vitro and in vivo approaches to demonstrate that TRPV4 expressed in airway epithelial cells triggers the secretion of major proinflammatory mediators such as chemokines and biologically active lipids, as well as a neutrophil recruitment in lung tissues. We characterized the contribution of cytosolic phospholipase A2, MAPKs, and NF-κB in TRPV4-dependent signaling. We also showed that 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids, i.e., four natural lipid-based TRPV4 agonists, are present in expectorations of CF patients. Also, TRPV4-induced calcium mobilization and inflammatory responses were enhanced in cystic fibrosis transmembrane conductance regulator-deficient cellular and animal models, suggesting that TRPV4 is a promising target for the development of new anti-inflammatory treatments for diseases such as CF.

Late N-acetylcysteine treatment prevents the deficits induced in the offspring of dams exposed to an immune stress during gestation.

Prenatal infection is a major stressful experience leading to enhanced susceptibility for mental illnesses in humans. We recently reported in rats, that oxidative stress and glutathione (GSH) shortage occurred in fetal male brain after lipopolysaccharide (LPS) to the dams and that these responses might be involved in the neurodevelopmental deficits observed in adolescent offspring. Furthermore, pretreatment with N-acetylcysteine (NAC) before LPS avoided both delayed synaptic plasticity and mnesic performance deficits. Since NAC is one of the few medications permitted in pregnant women, this study evaluated the ability of NAC to serve as a protective therapy even after the LPS challenge. Pregnant rats received a single ip injection of E. coli LPS, two days before delivery, and were given NAC in their tap water after the LPS. GSH was evaluated at the time of its expected drop in the hippocampus of male fetuses, whereas long-term potentiation (LTP) in the CA1 area of the hippocampus and spatial memory in the water-maze were recorded in 28-day-old male offspring. Post-treatment with NAC, four hours after the LPS challenge fully prevented the drop in the GSH hippocampal content. LTP, as well as spatial learning were completely protected. NAC administration at delivery also partially restored the LTP whereas post-treatment two days later was inefficient. Another set of dams were supplemented with alpha-tocopherol prior to LPS exposure, enhancing the alpha-tocopherol levels in fetal hippocampus. This treatment did not prevent the LPS-induced synaptic plasticity impairment. These results point to fetal hippocampal GSH as a major target of the detrimental effects of in utero LPS challenge. The therapeutic window of NAC extends up to birth, suggesting that this drug might be clinically useful even after an immuno-inflammatory episode.

Alpha-tocopherol-mediated long-lasting protection against oxidative damage involves an attenuation of calcium entry through TRP-like channels in cultured hippocampal neurons.

We have reported that a transient treatment of hippocampal neurons with alpha-tocopherol induced a long-lasting protection against oxidative damage mediated by Fe(2+) ions. This protection required protein synthesis. Here, we have studied whether this "hyposensitivity" to oxidative stress could be linked to an altered Ca(2+) homeostasis. Fe(2+) ions triggered a Ca(2+) entry which was required for Fe(2+) ion-induced toxicity. This influx was sensitive to blockers of TRP-like nonspecific Ca(2+) channels, including Ruthenium Red, La(3+), and Gd(3+) ions which also prevented the Fe(2+) ion-induced toxicity and oxidative stress as revealed by protein carbonylation status. The pretreatment with alpha-tocopherol resulted in a reduction of the Ca(2+) increase induced by Fe(2+) ions and masked the blocking effect of La(3+) ions. Moreover, such a pretreatment reduced the capacitive Ca(2+) entries (CCE) observed after metabotropic glutamate receptor stimulation, which are known to involve TRP-like channels. By contrast, in a model of "hypersensitivity" to oxidative stress obtained by chronic stimulation of glucocorticoid receptors, we observed an exacerbation of the various effects of Fe(2+) ions, i.e., cellular toxicity and Ca(2+) increase, and the glutamate-stimulated CCE. Therefore, we conclude that the long-lasting neuroprotection induced by alpha-tocopherol pretreatment likely results from an attenuation of Ca(2+) entries via TRP-like channels.

Neurodevelopmental damage after prenatal infection: role of oxidative stress in the fetal brain.

Prenatal infection is a major risk responsible for the occurrence of psychiatric conditions in infants. Mimicking maternal infection by exposing pregnant rodents to bacterial endotoxin lipopolysaccharide (LPS) also leads to major brain disorders in the offspring. The mechanisms of LPS action remain, however, unknown. Here, we show that LPS injection during pregnancy in rats, 2 days before delivery, triggered an oxidative stress in the hippocampus of male fetuses, evidenced by a rapid rise in protein carbonylation and by decreases in alpha-tocopherol levels and in the ratio of reduced/oxidized forms of glutathione (GSH/GSSG). Neither protein carbonylation increase nor decreases in alpha-tocopherol levels and GSH/GSSG ratio were observed in female fetuses. NMDA synaptic currents and long-term potentiation in CA1, as well as spatial recognition in the water maze, were also impaired in male but not in female 28-day-old offspring. Pretreatment with the antioxidant N-acetylcysteine prevented the LPS-induced changes in the biochemical markers of oxidative stress in male fetuses, and the delayed detrimental effects in male 28-day-old offspring, completely restoring both long-term potentiation in the hippocampus and spatial recognition performance. Oxidative stress in the hippocampus of male fetuses may thus participate in the neurodevelopmental damage induced by a prenatal LPS challenge.

FHL2 Regulates Natural Killer Cell Development and Activation during Streptococcus pneumoniae Infection.

Recent in silico studies suggested that the transcription cofactor LIM-only protein FHL2 is a major transcriptional regulator of mouse natural killer (NK) cells. However, the expression and role of FHL2 in NK cell biology are unknown. Here, we confirm that FHL2 is expressed in both mouse and human NK cells. Using FHL2-/- mice, we found that FHL2 controls NK cell development in the bone marrow and maturation in peripheral organs. To evaluate the importance of FHL2 in NK cell activation, FHL2-/- mice were infected with Streptococcus pneumoniae. FHL2-/- mice are highly susceptible to this infection. The activation of lung NK cells is altered in FHL2-/- mice, leading to decreased IFNγ production and a loss of control of bacterial burden. Collectively, our data reveal that FHL2 is a new transcription cofactor implicated in NK cell development and activation during pulmonary bacterial infection.

Metabotropic glutamate receptors as drug targets.

L-glutamate (Glu), the main excitatory amino acid neurotransmitter in the mammalian central nervous system, is involved in many physiological functions, including learning and memory, but also in toxic phenomena occurring in numerous degenerative or neurological diseases. These functions mainly result from its interaction with Glu receptors (GluRs). The broad spectrum of roles played by glutamate derived from the large number of membrane receptors, which are currently classified in two main categories, ionotropic (iGluRs) and metabotropic (mGluRs) receptors. The iGluRs are ion channels, permeant to Na(+) (Ca(2+)) while the mGluRs belongs to the superfamily of G-protein coupled receptors (GPCRs). Despite continuous efforts over more than two decades, the use of iGluR agonists or antagonists to improve or inhibit excitatory transmission in pathological states still remains a major challenge, though the discovery and development of recent molecules may prove it worthwhile. This probably results form the vital role of fast excitatory transmission in many fundamental physiological functions. Since the discovery of mGluRs, hope has emerged. Indeed, mGluRs are mainly involved in the regulation of fast excitatory transmission. Consequently, it was logically thought that modulating mGluRs with agonists or antagonists might lead to more subtle regulation of fast excitatory transmission than by directly blocking iGluRs. As a result of intensive investigation, new drugs permitting to discriminate between these receptors have emerged. Moreover, a new class of molecules acting as negative or positive allosteric modulators or mGluRs is now available and appears to be promising. In the following, we will review the classification of mGluRs and the functions in which mGluRs are involved. We will focus on their potential as therapeutic targets for improving numerous physiological functions and for different neurodegenerative and neuropsychiatric disorders, which are related to malfunction of Glu signaling in human beings.