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Anuj Singla, Deepa Talreja, Ashok Kumar; Interplay of NLRP3 Inflammasome Complex and TLR2 in Staphylococcus Aureus Endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2770.
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Several studies have demonstrated the activation of the NLRP3 inflammasome in response to microbial infections. Previous studies from our lab have shown the involvement of TLR2 in S. aureus-induced inflammation in the retina. The present study investigates whether NLRP3 inflammasome is activated in staphylococcal endophthalmitis and if it interplays with TLR2.
Wild type (WT) and TLR2-/- C57BL6 mice were infected intra-vitreally with S. aureus (RN6390) to induce endophthalmitis. At desired time points (4 to 24 h), the retinas were eviscerated from the eyes, followed by protein extraction, RNA extraction and cDNA synthesis. Expression of NLRP3 inflammasome associated genes and inflammatory cytokines genes were assessed by Taqman probe qRT-PCR. The protein levels were assessed by dot blot and ELISA.
S. aureus significantly increased the expression of NLRP3, Pycard/ASC, Panx1, and IL-1β in the retinas of WT mice compared to the normal and PBS injected controls. The time-course studies revealed that maximal expression of NLRP3 and IL1β was observed at 12 h post infection (p.i.). As compared to the WT mice, the TLR2-/- mice had a significantly lower expression of inflammasome complex genes at all-time points tested (8 h, 12 h and 24 h). Moreover, the retinas of mice infected with live S. aureus had significantly higher expression of NLRP3 and IL-1β compared to those infected with heat-inactivated S. aureus.
These findings indicate that NLRP3 inflamasome complex is activated in S.aureus endophthalmitis and there is interplay with TLR2 in generating an inflammatory response. The differential expression of NLRP3 in live versus heat-inactivated retina warrants further investigation to assess which components of S.aureus are involved in inducing the NLRP3 inflammasome pathway.
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