Fig 1: Comparison of molecules related to inflammasome activation quantified in BAL between patients with the anti-synthetase syndrome (ASSD) and systemic sclerosis (SSc). The cellularity was determined by counting with a Neubauer hemocytometer (A,B); quantifying cytokine concentration in BAL was performed by commercial ProcartaPlex system (C,D); the caspase-1 activity was quantified by fluorometry (E). Finally, the concentration of LDH and NLRP3 was quantified by ELISA (F,G). Comparisons between groups were made using the Mann–Whitney U test, and the results of the statistical inference were confirmed with the Hodges–Lehmann test.
Fig 2: NLRP3 depletion in microglia reduces disc degeneration and associated pain. The effects of altering NLRP3 levels in microglia on disc degeneration and associated pain were examined in a mouse model for LDD. A total of 8 groups of mice were included in this experiment. Group 1, NLRP3 (fx/fx) mice received sham operation (Sham); Group 2: NLRP3 (fx/fx) mice received LDD induction (LDD); Group 3: NLRP3mut mice received sham operation; Group 4: NLRP3mut mice received LDD induction; Group 5, Tmem119p-CreERT2; NLRP3 (fx/fx) mice received sham operation; Group 6: Tmem119p-CreERT2; NLRP3 (fx/fx) mice received LDD induction; Group 7: Tmem119p-CreERT2; NLRP3mut mice received sham operation; Group 8: Tmem119p-CreERT2; NLRP3mut mice received LDD induction. Mice were analyzed 8 weeks after LDD or at age of 23-week-old. (A, B) Surgical induction of LDD and the quantification of disc degeneration were performed, shown by representative images (A) and by quantification for degenerative scores (B). (C) A Von Frey filament test for pain evaluation, shown by the relative mechanically induced withdrawal threshold and by thermally induced withdrawal latency of the paw (normalized to those from NLRP3mut (=1)). *p<0.05. ns: no significance.
Fig 3: NLRP3 depletion in microglia reduces phagocytosis potential and release of pro-inflammatory cytokines. (A) Phagocytosis for zymosan was assessed in sorted disc microglia from mice with microglia-specific alteration in NLRP3 expression. (B) ELISA for IL-1β, TNFα, IFNɣ, ARG1 and CD163 in sorted disc microglia from mice with microglia-specific alteration in NLRP3 expression. The relative levels to those from NLRP3mut (=1) were shown. *p<0.05. ns, non-significant.
Fig 4: NLRP3 is exclusively expressed in disc microglia. Single cell expression profile for mouse spinal cord was obtained from Panglaodb. (A–F) In all analyzed 6 mouse spinal cord samples, NLRP3 (blue rectangle) was exclusively expressed in disc microglia clusters (red rectangle).
Fig 5: Disc NLRP3 levels correlate with the pain and disc degeneration level in LDD patients. Disc specimens from 24 participants who had different levels of Thompson classification of the degeneration and scores for pain were analyzed. (A, B) The NLRP3 protein levels in disc tissue were quantified by ELISA in all 24 specimens. Reads of NLRP3 OD values at 450nm were presented. The correlation between NLRP3 protein levels and pain score (A, r2 = 0.85, p<0.0001) or Thompson classification of the degeneration level (B, p=0.003) was assessed.
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