Activation of the Sphingosine 1 Phosphate-Rho Pathway in Pterygium and in Ultraviolet-Irradiated Normal Conjunctiva

Conjunctival Expression of Toll-Like Receptor 3 Plays a Pathogenic Role in the Formation of Ultraviolet Light-Induced Pterygium

Purpose

Toll-like receptor 3 (TLR3), as a damage-associated molecular pattern sensor, can detect self-RNA released from necrotic cells induced by ultraviolet B (UVB) radiation exposure. Pterygium formation is believed to be a tumorigenesis-like process induced by UVB exposure. In this study, we aimed to investigate the expression pattern of TLR3 in pterygium specimens and cultured pterygial epithelial cells (PECs).

Methods

Human pterygium and ipsilateral pterygium-free conjunctiva from the same patients were used in this study. The expression of TLR3 and nuclear factor-kappa B (NF-κB) was investigated in these specimens. PECs were exposed to UVB radiation to determine the effect of UVB on the expression of TLR3 and the activation of NF-κB.

Results

The immunofluorescence study showed stronger TLR3 expression in superficial epithelial cells in the pterygial epithelium in comparison with the normal conjunctival epithelium. The expression of TLR3 decreased in intensity from the superficial epithelium toward the basal cell layer, implying a correlation between UVB exposure and TLR3 expression. Differential TLR3 expression patterns in pterygial and conjunctival tissues were also found in quantitative PCR analyses. PECs after UVB irradiation had higher protein levels of TLR3 and phospho-NF-κB than those of the PECs without irradiation. Immunofluorescence studies showed that UVB irradiation induced the nuclear translocation of NF-κB in the PECs. In PECs with the targeted TLR3 gene silencing, the expression of phospho-NF-κB was not induced by UVB irradiation.

Conclusions

Our results indicate that UVB exposure, TLR3 expression, and NF-κB activation may be a critical sequence that leads to the formation of pterygium.

The sphingosine-1-phosphate/RhoA/Rho associated kinases/myosin light chain pathway in detrusor of female rats is down-regulated in response to ovariectomy

BACKGROUND

Dysuria is one of the main symptoms of genitourinary syndrome of menopause, which causes serious disruption to the normal life of peri-menopausal women. Studies have shown that it is related to decrease of detrusor contractile function, but the exact mechanism is still poorly understood. Previous results have suggested that the sphingosine-1-phosphate (S1P) pathway can regulate detrusor contraction, and this pathway is affected by estrogen in various tissues. However, how estrogen affects this pathway in the detrusor has not been investigated. In this study, we detected changes of the S1P/RhoA/Rho associated kinases (ROCK)/myosin light chain (MLC) pathway in the detrusor of ovariectomized rats in order to explore the underlying mechanism of dysuria during peri-menopause.

METHODS

Thirty-six female Sprague-Dawley rats were randomly divided into SHAM (sham operation), OVX (ovariectomy), and E groups (ovariectomy + estrogen), with 12 rats in each group. We obtained bladder detrusor tissues from each group and examined the mRNA and protein levels of the major components of the S1P/RhoA/ROCK/MLC pathway using quantitative real-time polymerase chain reaction and Western blotting, respectively. We also quantified the content of S1P in the detrusor using an enzyme linked immunosorbent assay. Finally, we compared results between the groups with one-way analysis of variance.

RESULTS

The components of the S1P pathway and the RhoA/ROCK/MLC pathway of the OVX group were significantly decreased, as compared with SHAM group. The percent decreases of the components in the S1P pathway were as follows: sphingosine kinase 1 (mRNA: 39%, protein: 45%) (both P < 0.05), S1P (21.73 ± 1.09 nmol/g vs. 18.86 ± 0.69 nmol/g) (P < 0.05), and S1P receptor 2/3 (S1PR2/3) (mRNA: 25%, 27%, respectively) (P < 0.05). However, the protein expression levels of S1PR2/3 and the protein and mRNA levels of SphK2 and S1PR1 did not show significant differences between groups (P > 0.05). The percent decreases of the components in the RhoA/ROCK/MLC pathway were as follows: ROCK2 (protein: 41%, mRNA: 36%) (both P < 0.05), p-MYPT1 (protein: 54%) (P < 0.05), and p-MLC20 (protein: 47%) (P < 0.05), but there were no significant differences in the mRNA and protein levels of RhoA, ROCK1, MYPT1, and MLC20 (all P > 0.05). In addition, all of the above-mentioned decreases could be reversed after estrogen supplementation (E group vs. SHAM group) (all P > 0.05).

CONCLUSION

In this study, we confirmed that ovariectomy is closely associated with the down-regulation of the S1P/RhoA/ROCK/MLC pathway in the rat detrusor, which may be one mechanism of dysuria caused by decreased contractile function of the female detrusor during peri-menopause.