Expressions of cyclooxygenase 1 and 2 in endotoxin-induced otitis media with effusion in the rat

The expression of VEGF and VEGFR in endotoxin induced otitis media with effusion in rats

OBJECTIVE

To investigate the expression and correlation of vascular endothelial growth factor (VEGF) and its receptor with hypoxia-inducible factor-1 α (HIF-1 α) in otitis media with effusion (OME).

METHODS

A rat model of OME was induced by injection of lipopolysaccharide (LPS) into the middle ear. Hematoxylin and eosin (HE) staining was used to observe the pathomorphological changes of the tympanic cavity in the middle ear of rats. Immunohistochemistry (IHC), western blotting and RT-qPCR were used to determine the mRNA and protein expression of VEGF, VEGFR-1, VEGFR-2 and HIF-1α in mucosa of tympanic cavity mucosa, respectively.

RESULTS

In the OME group, the epithelial space of the middle ear mucosa was significantly thickened and infiltration of a large number of inflammatory cells was found on postoperative day (POD), and the otitis media basically subsided 2 weeks after operation. VEGF mRNA expression was significantly increased on POD 1, and its protein expression peaked on POD 3. HIF-1α mRNA expression was significantly increased and peaked on POD 1, while its protein expression began to increase on POD 3 and was significantly expressed in the middle ear mucosal epithelium. HIF-1α mRNA showed a positive correlation with VEGF mRNA and VEGFR-1 mRNA expression.

CONCLUSION

VEGF mainly plays a role in the acute phase of OME, and it is abundantly expressed mediated by HIF-1α. And then it play a role in vasodilatation and increase of vascular permeability, thus promoting the generation of middle ear effusion.

Formulation Optimization and Ex Vivo and In Vivo Evaluation of Celecoxib Microemulsion-Based Gel for Transdermal Delivery

Celecoxib (CXB) is a poorly aqueous solubility sulfonamide non-steroidal anti-inflammatory drug (NSAID). Hence, the formulation of CXB was selected for solubilization and bioavailability. To find out suitable formulation for microemulsion, the solubility of CXB in triacetin (oil phase), Tween 80 (surfactant), and Transcutol-P (co-surfactant) was screened respectively and optimized by using orthogonal experimental design. The Km value and concentration of oil, S_mix, and water were confirmed by pseudo-ternary phase diagram studies and central composite design. One percent carbopol 934 was added to form CXB microemulsion-based gel. The final formulation was evaluated for its appearance, pH, viscosity, stability, drug content determination, globule size, and zeta potential. Its ex vivo drug permeation and the in vivo pharmacokinetic was investigated. Further research was performed to ensure the safety and validity by skin irritation study and in vivo anti-inflammatory activity study. Ex vivo permeation study in mice was designed to compare permeation and transdermal ability between microemulsion formulation and conventional gel. The results revealed that optimized microemulsion-based gel gained higher permeation based on smaller globule size and high drug loading of microemulsion. Transdermal ability was also greatly improved. Bioavailability was compared to market Celebrex® by the in vivo pharmacokinetic study in rabbits. The results indicated that CXB microemulsion-based gel had better bioavailability than Celebrex®.

Lipopolysaccharide-induced middle ear inflammation disrupts the cochlear intra-strial fluid-blood barrier through down-regulation of tight junction proteins

Middle ear infection (or inflammation) is the most common pathological condition that causes fluid to accumulate in the middle ear, disrupting cochlear homeostasis. Lipopolysaccharide, a product of bacteriolysis, activates macrophages and causes release of inflammatory cytokines. Many studies have shown that lipopolysaccharides cause functional and structural changes in the inner ear similar to that of inflammation. However, it is specifically not known how lipopolysaccharides affect the blood-labyrinth barrier in the stria vascularis (intra-strial fluid–blood barrier), nor what the underlying mechanisms are. In this study, we used a cell culture-based in vitro model and animal-based in vivo model, combined with immunohistochemistry and a vascular leakage assay, to investigate lipopolysaccharide effects on the integrity of the mouse intra-strial fluid–blood barrier. Our results show lipopolysaccharide-induced local infection significantly affects intra-strial fluid–blood barrier component cells. Pericytes and perivascular-resident macrophage-like melanocytes are particularly affected, and the morphological and functional changes in these cells are accompanied by substantial changes in barrier integrity. Significant vascular leakage is found in the lipopolysaccharide treated-animals. Consistent with the findings from the in vivo animal model, the permeability of the endothelial cell monolayer to FITC-albumin was significantly higher in the lipopolysaccharide-treated monolayer than in an untreated endothelial cell monolayer. Further study has shown the lipopolysaccharide-induced inflammation to have a major effect on the expression of tight junctions in the blood barrier. Lipopolysaccharide was also shown to cause high frequency hearing loss, corroborated by previous reports from other laboratories. Our findings show lipopolysaccharide-evoked middle ear infection disrupts inner ear fluid balance, and its particular effects on the intra-strial fluid–blood barrier, essential for cochlear homeostasis. The barrier is degraded as the expression of tight junction-associated proteins such as zona occludens 1, occludin, and vascular endothelial cadherin are down-regulated.

Assessment of the potential ototoxicity of high-dose celecoxib, a selective cyclooxygenase-2 inhibitor, in rats

OBJECTIVE

To evaluate the potential ototoxicity of high-dose celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor.

STUDY DESIGN

Prospective animal study.

SETTING

Laboratory.

METHODS

Twenty adult male Sprague Dawley rats were divided into 2 groups for hearing and tinnitus tests, respectively. The auditory brain-stem response (ABR) and the gap prepulse inhibition of acoustic startle (GPIAS) were used as indicators of hearing loss and tinnitus, respectively, and were measured before and at 2, 4, 6, 8, 12, 24, and 48 hours after administration of celecoxib (2 g/kg) via gavage.

RESULTS

ABR threshold and wave III latencies did not increase significantly at any frequency following celecoxib administration, at any time point (P > .05). GPIAS remained below 30% after celecoxib, from a baseline of 20.03% ± 3.62%; no change was significant.

CONCLUSION

High-dose celecoxib (2 g/kg), a selective COX-2 inhibitor, did not cause hearing loss or tinnitus in Sprague Dawley rats within 48 hours of administration. Further studies are needed to explore the roles played by COX-related mechanisms when nonselective COX inhibitors induce ototoxicity.

Cytokine responses in the common cold and otitis media

Cytokines are a group of diverse molecules that influence the function of every organ system. They are most well studied in their effects on the immune system and their integral role in mediating inflammation. The common cold and otitis media are two such disease states, and much has been learned about the various effects of cytokines in each disease. Most often the viruses isolated include rhinovirus (RV), respiratory syncytial virus (RSV), adenovirus, coronavirus, and picornavirus. Otitis media, sinusitis, bronchiolitis, pneumonia, and asthma exacerbation are commonly accepted as complications of viral upper respiratory tract infections. Furthermore, otitis media and upper respiratory infections are inextricably linked in that the majority (>70 %) of cases of acute otitis media occur as complications of the common cold. Cytokine polymorphisms have been associated with the severity of colds as well as the frequency of otitis media. This article attempts to update the reader on various studies that have recently been published regarding the role of cytokines in these two disease entities.

Effect of caffeic acid phenethyl ester (CAPE) on H₂O₂ induced oxidative and inflammatory responses in human middle ear epithelial cells

OBJECTIVE

Acute otitis media (OM) is a common pediatric disease. Recent research into the pathogenesis of OM has focused on oxidative damage, induced by oxygen free radicals, to the middle ear mucosa along with inflammation. Caffeic acid phenethyl ester (CAPE) is a biologically active ingredient of propolis honey bees, with antioxidative and anti-inflammatory activities. The effect of CAPE on hydrogen peroxide (H(2)O(2))-induced inflammatory and oxidative reactions in the middle ear is still not known. The aim of this study was to evaluate the anti-inflammatory and antioxidative effects of CAPE on cultured human middle ear epithelial cells (HMEECs).

METHODS

The inflammatory injury of H(2)O(2) and the anti-inflammatory effect of CAPE were determined by measuring levels of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α and COX-2) with real-time reverse transcription polymerase chain reaction and Western blot analysis. Oxidative stress induced by H(2)O(2) and antioxidative effects of CAPE were evaluated directly by reactive oxygen species (ROS) production using flow cytometric analysis of 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H(2)DCFDA), and indirectly by the expression of superoxide dismutase (SOD) using Western blot analysis. The effect of CAPE was compared with N-acetyl cysteine (NAC) which has well-known antioxidative and anti-inflammatory effects.

RESULTS

CAPE significantly inhibited H(2)O(2)-induced upregulation of TNF-α and COX-2 expression in a dose and time dependent manner. ROS accumulation induced by H(2)O(2) stimulation was decreased by CAPE pretreatment. Induced SOD expression after H(2)O(2) stimulation was diminished by CAPE pretreatment. The anti-inflammatory and antioxidative effects of CAPE were similar to those of NAC.

CONCLUSIONS

These findings suggest that inflammation induced by H(2)O(2) can be inhibited by CAPE via inhibition of the expression of pro-inflammatory cytokines such as TNF-α and COX-2. Furthermore, CAPE has antioxidative effects, which decreases the need for endogenous SOD expression.

Lipopolysaccharide induces proinflammatory cytokines and chemokines in experimental otitis media through the prostaglandin D2 receptor (DP)-dependent pathway

Otitis media is one of the most common and intractable ear diseases, and is the major cause of hearing loss, especially in children. Multiple factors affect the onset or development of otitis media. Prostaglandin D₂ is the major prostanoid involved in infection and allergy. However, the role of prostaglandin D₂ and prostaglandin D2 receptors on the pathogenesis of otitis media remains to be determined. Recent studies show that D prostanoid receptor (DP) and chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cells (CRTH2) are major prostaglandin D₂ receptors. In this study, homozygous DP single gene-deficient (DP⁻(/)⁻) mice, CRTH2 single gene-deficient (CRTH2⁻(/)⁻) mice and DP/CRTH2 double gene-deficient (DP⁻(/)⁻ CRTH2⁻(/)⁻) mice were used to investigate the role of prostaglandin D₂ and its receptors in otitis media. We demonstrate that prostaglandin D₂ is induced by lipopolysaccharide (LPS), a major component of Gram-negative bacteria, and that transtympanic injection of prostaglandin D₂ up-regulates macrophage inflammatory protein 2 (MIP-2), interleukin (IL)-1β and IL-6 in the middle ear. We also show that middle ear inflammatory reactions, including infiltration of inflammatory cells and expression of MIP-2, IL-1β and IL-6 induced by LPS, are reduced significantly in DP⁻(/)⁻ mice and DP⁻(/)⁻ CRTH2⁻(/)⁻ mice. CRTH2⁻(/)⁻ mice display inflammatory reactions similar to wild-type mice. These findings indicate that prostaglandin D₂ may play significant roles in LPS-induced experimental otitis media via DP.

Guggulsterone suppresses LPS induced inflammation of human middle ear epithelial cells (HMEEC)

OBJECTIVE

Guggulsterone is a bioactive constituent of resinous sap originating from the guggul tree, Commiphora mukul, which has been used over several thousands of years to treat various diseases, including atherosclerosis, rheumatism, and obesity. However, the effect of guggulsterone inflammatory reactions induced by lipopolysaccharide (LSP) is not known. The aim of this study was to evaluate the anti-inflammatory effect of guggulsterone on cultured human middle ear epithelial cells (HMEEC).

METHODS

The effect of guggulsterone on LPS-induced tumor necrosis factor-alpha (TNF-α) and cyclooxygenase-2 (COX-2) expression was evaluated in HMEEC by real-time reverse transcription polymerase chain reaction (RT-PCR). LPS-induced COX-2 production and degradation of the inhibitor kB-alpha (IkB-α) were determined by Western blot analysis.

RESULTS

Guggulsterone significantly inhibited LPS-induced upregulation of TNF-α and COX-2 in a dose-dependent manner. COX-2 protein production by LPS was significantly suppressed by the guggulsterone pretreatment. Furthermore, LPS-induced IkB-α degradation was suppressed by the guggulsterone pretreatment.

CONCLUSIONS

These results show that the guggulsterone has inhibitory effect on TNF-α expression and COX-2 production and it may be mediated through its inhibition of nuclear factor-kB activation. Our findings provide an insight into the molecular mechanisms underlying the anti-inflammatory activities of guggulsterone in relationship to otitis media.