Background/Purpose: Osteoarthritis (OA) is characterized by an imbalance between catabolism and anabolism, higher than normal levels of matrix metalloproteinases (MMPs), an increase in inflammatory markers (i.e. interleukins (ILs) or eicosanoids), and an increase in reactive oxygen species (ROS). Hydrogen sulfide (H₂S) is a novel endogenous gas and signaling molecule. Here we looked into the effects of H₂S donors as anti-catabolic, anti-oxidant and anti-inflammatory agents in human articular chondrocytes (hCs) from OA tissue.

Methods: We used an in vitro model in which hCs were stimulated with one of two H₂S donors: NaHS or GYY4137; 50mM to 1000mM; 48h; H₂S-only-treated (S)-group. In some tests, IL1β (5ng/mL) or Lipopolysaccharide (LPS, 1µg/mL) were also added. We chose MMP1, 3 and 13, collagen–II (COLII) and aggrecan (ACAN) as matrix degradation and synthesis markers. The prostaglandin E2 (PGE2) synthesis pathway and IL6, for inflammation. Superoxide dismutase(SOD)-2 and catalase (CAT) as scavenger enzymes. ROS synthesis (mitochondrial(M)-ROS and cytoplasmatic(C)‑ROS) was measured with cell cytometry. Effects on gene expression were quantified with qRT-PCR and those on proteins with immunocytochemistry (ICC) or enzymatic immunoassays (EIA).

Results: 1.Catabolism: The two H₂S donors reduced MMP3 and MMP13 expression in the S-group, although p>0.05. On IL1β-group, MMP3 and 13 (Fig.1A) expressions in the IL1β condition (182 and 52 fold vs. the basal (B)), were reduced to 124 and 10 (1000mM GYY4137, respect.) and 91 and 13 (1000mM NaHS, respect.). There was a marked reduction in MMP3 protein levels (ICC). 2.Anabolism: 200mM NaHS and GYY4137 counteracted COLII and ACAN repressed expression on the IL1β-group. 3.Inflammation: H₂S donors reduced IL-6 (Fig.1B), cyclooxygenase (COX)-2 mRNA expression in the IL1β-group without significantly affecting COX-1. 4.ROS: Only 200mM NaHS reduced C-ROS in the S-Group (from 27.7±5.7 to 21.5±1.9UA). On the IL1β-group, H₂S donors did not reduce ROS. SOD2 (Fig.1C) and CAT expression levels were unaffected (p>0.05) in either group. Only 200mM GYY4137 reduced M‑ROS in the LPS-Group to B level.  

Conclusion: Exogenous H₂S donors NaHS and GYY4137 show anti-inflammatory, anti-catabolic and pro-anabolic properties in an in vitro model with human OA chondrocytes. However, in the conditions of the present study, they do not reduce pathological ROS levels found in OA chondrocytes and do not increase the anti-oxidant capacity of the cells.