Biomechanical Thresholds Regulate Inflammation through the NF-κB Pathway: Experiments and Modeling

BACKGROUND: During normal physical activities cartilage experiences dynamic compressive forces that are essential to maintain cartilage integrity. However, at non-physiologic levels these signals can induce inflammation and initiate cartilage destruction. Here, by examining the pro-inflammatory signaling networks, we developed a mathematical model to show the magnitude-dependent regulation of chondrocytic responses by compressive forces. METHODOLOGY/PRINCIPAL FINDINGS: Chondrocytic cells grown in 3-D scaffolds were subjected to various magnitudes of dynamic compressive strain (DCS), and the regulation of pro-inflammatory gene expression via activation of nuclear factor-kappa B (NF-kappaB) signaling cascade examined. Experimental evidences provide the existence of a threshold in the magnitude of DCS that regulates the mRNA expression of nitric oxide synthase (NOS2), an inducible pro-inflammatory enzyme. Interestingly, below this threshold, DCS inhibits the interleukin-1beta (IL-1beta)-induced pro-inflammatory gene expression, with the degree of suppression depending on the magnitude of DCS. This suppression of NOS2 by DCS correlates with the attenuation of the NF-kappaB signaling pathway as measured by IL-1beta-induced phosphorylation of the inhibitor of kappa B (IkappaB)-alpha, degradation of IkappaB-alpha and IkappaB-beta, and subsequent nuclear translocation of NF-kappaB p65. A mathematical model developed to understand the complex dynamics of the system predicts two thresholds in the magnitudes of DCS, one for the inhibition of IL-1beta-induced expression of NOS2 by DCS at low magnitudes, and second for the DCS-induced expression of NOS2 at higher magnitudes. CONCLUSIONS/SIGNIFICANCE: Experimental and computational results indicate that biomechanical signals suppress and induce inflammation at critical thresholds through activation/suppression of the NF-kappaB signaling pathway. These thresholds arise due to the bistable behavior of the networks originating from the positive feedback loop between NF-kappaB and its target genes. These findings lay initial groundwork for the identification of the thresholds in physical activities that can differentiate its favorable actions from its unfavorable consequences on joints

Once daily mometasone furoate aqueous nasal spray is as effective as twice daily beclomethasone dipropionate for treating perennial allergic rhinitis patients

Background: Perennial allergic rhinitis is chronic and persistent, may lead to a constellation of secondary complaints including sinusitis, mouth-breathing, and some symptoms resembling a permanent cold, and often requires constant medical intervention. Well-tolerated nasal corticosteroids, alone or in combination with antihistamines, have been found to be very effective in treating this condition. Objective: To compare the effectiveness and tolerability of mometasone furoate aqueous suspension, a new once daily nasal spray, to placebo vehicle and to beclomethasone dipropionate, administered twice daily, in patients with perennial allergic rhinitis. Methods: This was a randomized, double-blind, placebo-controlled, double-dummy, parallel group study, in 427 patients age 12 years and older at 24 centers in Canada and Europe. Patients allergic to at least one perennial allergen, confirmed by medical history, skin testing, and adequate symptomatology were eligible to receive one of the following regimens for 3 months: mometasone furoate, 200 mu g once daily; beclomethasone dipropionate, 200 mu g twice daily (400 mu g total dose); or placebo vehicle control. The primary efficacy variable was the change from baseline in total AM plus PM diary nasal symptom score over the first 15 days of treatment. Results: Three hundred eighty-seven patients were valid for efficacy. For the primary efficacy variable, mometasone furoate was significantly (P less than or equal to .01) more effective than placebo and was indistinguishable from beclomethasone dipropionate. Similar trends were seen among individual symptoms, physician symptom evaluations, and therapeutic response. There was no evidence of tachyphylaxis. All treatments were well tolerated. Conclusions: Mometasone furoate nasal spray adequately controls symptoms of perennial allergic rhinitis, offers the advantage of once daily treatment, and is well tolerated