Mourad Benallaoua

Université René Descartes - Paris 5, Lutetia Parisorum, Île-de-France, France

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Publications (8)37.28 Total impact

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    ABSTRACT: We investigated the role of heme oxygenase-1 (HO-1), a powerful anti-inflammatory and anti-oxidant enzyme, in modulating cigarette smoke (CS)-induced mucus secretion. In both rats and mice, 5-day CS exposure increased HO-1 expression and activity, mucus secretion, MUCIN 5AC (MUC5AC) gene and protein expression, and local inflammation, along with up-regulation of dual oxidase 1 gene expression and both the activity and phosphorylation of the epidermal growth factor receptor, which is involved in MUC5AC induction. Pharmacological induction of HO-1 prevented these actions and inhibition of HO-1 expression by a specific siRNA potentiated them. In French participants to the European Community Respiratory Health Survey II (n = 210, 30 to 53 years of age, 50% males) exposed to CS, a significant increase in the percentage of participants with chronic sputum was observed in those harboring at least one allele with a long (GT)(n) in the HO-1 promoter gene (>33 repeats), which is associated with a low level of HO-1 protein expression, compared with those with a short number of (GT)n repeats (21.7% versus 8.6%, P = 0.047). No such results were observed in those who had never smoked (n = 297). We conclude that HO-1 has a significant protective effect against airway mucus hypersecretion in animals and humans exposed to CS.
    American Journal Of Pathology 10/2008; 173(4):981-92. · 4.60 Impact Factor
  • Osteoarthritis and Cartilage 01/2008; 16. · 4.26 Impact Factor
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    ABSTRACT: To determine the consequences of pharmacologic up-regulation of heme oxygenase 1 (HO-1), and inhibition of HO-1 by injection of an anti-HO-1 small interfering RNA (siRNA), in vivo in the acute phase of a mouse model of nonautoimmune arthritis. In the K/BxN mouse serum transfer model, which mimics human inflammatory arthritis without lymphocyte influence, HO-1 was up-regulated by intraperitoneal injection of cobalt protoporphyrin IX (CoPP), a potent pharmacologic inducer, and was inhibited using a specific siRNA. The clinical progress of arthritis was monitored by measurement of paw thickness. Interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha (TNFalpha), serum antioxidant, and nitric oxide (NO) levels, prostaglandin E(2) (PGE(2)) production, and matrix metalloproteinase 9 (MMP-9) activity were measured in serum. At the end of the experiments, joints were examined for immunohistopathologic changes. Intraperitoneal injection of CoPP alleviated disease symptoms, such as joint swelling, cartilage degradation, and proliferation of inflammatory tissue in joints, in the acute phase of inflammatory arthritis. The CoPP-induced expression of HO-1 in the joints and liver was associated with marked decreases in IL-1beta, IL-6, and TNFalpha levels, PGE(2) secretion, and MMP-9 activity in serum, and with a marked increase in systemic antioxidant activity. In contrast, NO production in serum and inducible NO synthase expression in chondrocytes were not affected by HO-1 induction. Specific inhibition of HO-1 by in vivo delivery of anti-HO-1 siRNA repressed the protective effects. Our data provide the first evidence that pharmacologically induced up-regulation of HO-1 triggers a robust protective antiinflammatory response in a model of nonautoimmune arthritis in mice. This suggests that exogenously induced HO-1 may have potential as therapy in the acute phase of inflammatory arthritis in humans.
    Arthritis & Rheumatology 09/2007; 56(8):2585-94. · 7.48 Impact Factor
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    ABSTRACT: To investigate the presence and functionality of oestrogen receptor alpha (ERalpha) in interleukin (IL)1beta-treated rabbit articular chondrocytes in culture, and to determine the mechanisms of 17beta oestradiol (E2) effects on IL1beta-induced inducible nitric oxide synthase (iNOS) expression. The presence and functionality of ERalpha were investigated by immunocytochemistry and transient expression of an E2-responsive reporter construct. iNOS expression and production were determined by transient expression of a chimeric iNOS promoter-luciferase construct and protein immunoblotting. Nitric oxide (NO) production was determined by the Griess reaction. DNA-binding activities of nuclear factor-kappaB (NF-kappaB) and activated protein 1 were determined by electrophoretic mobility shift assay (EMSA)-ELISA assays. Nuclear translocation of p65 was studied by immunocytochemistry. ERalpha was identified in the nucleus of chondrocytes. ERalpha efficiently transactivated a transiently expressed E2-responsive construct. On IL1beta treatment, ERalpha partially diffused from its nuclear localisation into the cytoplasm and its transactivation ability was impaired. Nevertheless, E2, tamoxifen and raloxifene efficiently inhibited IL1beta-induced NO production (-34%, -31% and -36%, respectively). E2 decreased IL1beta-induced iNOS protein expression (-40%). Transient expression of an iNOS promoter construct strongly suggested that iNOS expression was inhibited at the transcriptional level, and EMSA-ELISA assays showed that E2 reduced (-60%) the IL1beta-induced p65 DNA-binding capacity. Finally, the p65 nuclear translocation induced by IL1beta was also strongly decreased by E2. Our data support a reciprocal antagonism between oestrogens and IL1beta, ultimately resulting in the decrease of cytokine-dependent NO production through transcriptional inhibition of iNOS expression. This effect was associated with selective inhibition of p65 DNA binding and nuclear translocation.
    Annals of the Rheumatic Diseases 04/2007; 66(3):345-50. · 9.11 Impact Factor
  • Revue Du Rhumatisme - REV RHUM. 01/2007; 74(10):1154-1154.
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    ABSTRACT: To determine whether peroxisome proliferator-activated receptor alpha (PPARalpha) agonists protect chondrocytes against the effects of interleukin-1beta (IL-1beta). PPARalpha expression and function in cultured rabbit articular chondrocytes were studied by Northern blotting, electrophoretic mobility shift assay, and transient expression of a luciferase reporter construct bearing the human IL-1 receptor antagonist (Il-1Ra) gene promoter. Chondrocytes were incubated in vitro with IL-1beta alone or in combination with CloFibrate (CloF) or other PPAR ligands. Proteoglycans were evaluated by 35S-sulfate incorporation, matrix metalloproteinase (MMP) levels were assessed by zymography and enzyme-linked immunosorbent assay (ELISA), and MMP messenger RNA (mRNA) levels were measured by Northern blotting and real-time reverse transcriptase-polymerase chain reaction. IL-1beta and IL-1Ra soluble contents were measured by ELISA. CloF counteracted IL-1beta-induced 35S-proteoglycan degradation, gelatinolytic activity, and MMP-1, -3, and -13 mRNA expression. CloF also maximized IL-1beta-induced endogenous production of soluble IL-1Ra (sIL-1Ra). This stimulating effect on IL-1Ra gene expression was shown, by transient expression assay, to be transcriptional. Inhibition of sIL-1Ra expression by a specific small interfering RNA suppressed the effect of CloF on IL-1beta-induced MMP expression. The stimulatory effect of CloF was enhanced by cotransfection with wild-type PPARalpha and abolished by a dominant-negative PPARalpha mutant. Fenofibrate and WY-14643 displayed a similar stimulating effect on the IL-1Ra promoter, while rosiglitazone did not. Two PPAR response elements, an NF-kappaB-binding site, and a CCAAT/enhancer binding protein-binding site were identified in the IL-1Ra promoter. All 4 sites were necessary for mediation of the effects of CloF. Our findings support the notion that there is a PPARalpha-dependent mechanism that inhibits IL-1beta function in chondrocytes, which operates via an increase in sIL-1Ra production.
    Arthritis & Rheumatology 05/2006; 54(4):1233-45. · 7.48 Impact Factor
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    ABSTRACT: Proteoglycan production is one of the major extracellular matrix components implicated in the dynamic process of intervertebral disc degeneration. Mechanical stress is an important modulator of the degeneration, but the underlying molecular mechanism at the proteoglycan level remains unclear. The aim of this work was to study the regulation of proteoglycan production by cyclic tensile stretch applied to intervertebral disc annulus fibrosus cells. Matrix metalloproteinases do not seem to be implicated in the regulation of proteoglycan production. By contrast, nitrite oxide production is induced by cyclic tensile stretch, in a time, intensity, and frequency dependant manner. Using a non-specific nitric oxide synthases inhibitor [NG-methyl-L-arginine (L-NMA)], we suppress totally the inhibition of proteoglycan production induced by cyclic tensile stretch suggesting the implication of nitric oxide synthases in the observed phenomenon. Introducing the transcriptional inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole or a more specific inhibitor of nitric oxide synthases II [N-iminoethyl-L-lysine (L-NIL)] did not affect the decreased proteoglycan production, which suggests a post-translational regulation. In contrast, N-omega nitro-L-arginine (L-NNA) a more specific inhibitor of NOS I and III abrogated the cyclic tensile stretch-dependant inhibition of proteoglycan production. These results suggest that cyclic tensile stretch regulates proteoglycan production through a post-translational mechanism involving nitrite oxide. This result could be of interest in the development of local therapeutic strategies aimed at controlling intervertebral disc degeneration.
    Biorheology 02/2006; 43(3-4):303-10. · 1.29 Impact Factor
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    ABSTRACT: Degeneration of the intervertebral disc is the main pathophysiological process implicated in low back pain and is a prerequisite to disc herniation. Clinically, mechanical forces are important modulators of the degeneration, but the underlying molecular mechanism is not known and needs investigation to identify the biological target. The aim of this work was to study, at the molecular level, the effects of cyclic tensile stretch (CTS) on the production of proteoglycan by intervertebral disc annulus fibrosus cells since proteoglycans seem to be implicated in the dynamic process of intervertebral disc degeneration. Such cells of rabbit were cultured at high density on plates with a flexible bottom. CTS was applied with use of a pressure-operated instrument to deform the plates. With CTS at 1% elongation (1 Hz frequency), the level of (35)S-labeled neosynthesized proteoglycans that accumulated in the cellular pool or were secreted in the culture medium did not change, but at 5% elongation, the level was significantly reduced after 8 h of stimulation (30 and 21%, respectively) and further reduced at 24 h (43 and 41%, respectively). Introducing the protein synthesis inhibitor cycloheximide had no effect on this result. Neither aggrecan and biglycan expression nor proteoglycan physical properties were modified. The level of nitrite oxide production significantly increased by 3.5 times after 8 h of 5% elongation. Introducing the nitric oxide synthase (NOS) inhibitors N(G)-methyl-l-arginine or N-omega nitro-l-arginine diminished the effects of CTS on the production of nitrite oxide and proteoglycans. By contrast, introducing N-iminoethyl-l-lysine (a more specific inhibitor of inductible NOS [iNOS]) had little or no effect. Taken together, these results suggest that cNOS activation seems to be more implicated in the 5% CTS modulation of proteoglycan production than iNOS activation. These results suggest that CTS can help regulate the intervertebral disc matrix by decreasing proteoglycan production through a post-translational regulation involving nitrite oxide. This result could be of interest in the development of local therapeutic strategies aimed at controlling intervertebral disc degeneration.
    Journal of Cellular Biochemistry 10/2003; 90(1):148-57. · 3.06 Impact Factor