HIV-1 Tat protein is a key neuropathological element in HIV associated neurogcognitive disorders (HAND); a type of cognitive syndrome thought to be at least partially mediated by increased levels of brain reactive oxygen species (ROS) and nitric oxide (NO). Methylsulfonylmethane (MSM) is a sulfur-containing compound known to reduce oxidative stress. This study was conducted to determine whether administration of MSM attenuates HIV-1 Tat induced oxidative stress in mouse neuronal cells. MSM treatment significantly decreased neuronal cell NO and ROS secretion. Further, MSM significantly reversed HIV-1 Tat mediated reductions in reduced glutathione (GSH) as well as HIV-1 Tat mediated increases in oxidized glutathione (GSSG). In addition, Tat reduced nuclear translocation of nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), a key nuclear promoter of antioxidant activity, while MSM increased its translocation to the nucleus in the presence of Tat. These results suggest that HIV-1 Tat reduces the resiliency of neuron cells to oxidative stress which can be reversed by MSM. Given the clinical safety of MSM, future preclinical in vivo studies will be required to further confirm these results in effort to validate MSM as a neuroprotectant in patients at risk of, or who are already diagnosed with, HAND.
Methylsulfonylmethane (MSM) is an organosulfur compound and the health benefits associated with MSM include inflammation. Although MSM has been shown to have various physiological effects, no study has yet focused on inflammasome activation. The inflammasome is a multiprotein complex that serves as a platform for caspase 1-dependent proteolytic maturation and secretion of interleukin-1β (IL-1β). In this study, we tested the effect of MSM on inflammasome activation using mouse and human macrophages. In our results, MSM significantly attenuated NLRP3 inflammasome activation in lipopolysaccharide-primed macrophages, although it had no effect on NLCR4 or AIM2 inflammasome activation. Extracts of MSM-enriched vegetables presented the same inhibitory effect on NLRP3 inflammasome activation as MSM. MSM also attenuated the transcriptional expression of IL-1α, IL-1β, IL-6, and NLRP3. Taken together, these results show that MSM has anti-inflammatory characteristics, interrupts NLRP3 inflammasome activation, and inhibits pro-cytokine expression. We further confirmed the intracellular mechanism of MSM in relation to NLRP3 inflammasome activation, followed by comparison with that of DMSO. Both chemicals showed a synergic effect on anti-NLRP3 activation and attenuated production of mitochondrial reactive oxygen species (ROS). Thus, MSM is a selective inhibitor of NLRP3 inflammasome activation and can be developed as a supplement to control several metabolic disorders.
Methylsulfonylmethane (MSM) is a non-toxic, natural organosulfur compound, which is known to possess antioxidant and anti-inflammatory activities. In recent years, MSM has been widely used as a dietary supplement for its beneficial effects against various diseases, especially arthritis. Despite being a popular supplement product, the mechanism of action of MSM is not well known. This study was designed to investigate the effects of MSM on cytotoxic signals induced by lipopolysaccharide (LPS) and interferon-gamma (IFN-γ) in RAW 264.7 macrophage-like cells. The results showed that MSM reversed apoptosis of RAW 264.7 macrophage-like cells at non-cytotoxic concentrations probably through the modulation of apoptotic proteins. After pre-treatment of cells with non-toxic doses of MSM; caspase-3 activation, p53 accumulation, cytochrome c release and Bax/Bcl-2 ratio were significantly decreased and full length poly ADP-ribose polymerase (PARP) was significantly increased. In addition, the loss of mitochondrial membrane potential was decreased with MSM pretreatment in activated macrophages. Since excess nitric oxide production causes apoptosis of macrophages, anti-apoptotic effects of MSM are thought to be mediated by its inhibitor effects on inducible nitric oxide synthase (iNOS) protein and nitric oxide levels. More interestingly, higher doses of MSM exhibited biphasic effects, inhibited cell viability, induced apoptosis of macrophages, increased caspase-3 activity and PARP cleavage. Thus, our results reveal the molecular mechanism of of MSM indicating that MSM supplementation may be beneficial for complications related to nitric oxide-dependent apoptosis in inflammatory conditions. However, the optimum concentration of MSM must be chosen carefully to elicit the desired effect.
AIMS: Reactive oxygen species (ROS) are highly diffusable and reactive molecules which modulate gene transcription, particularly of pro-inflammatory cytokines which play a crucial role in the nascency and progression of chronic inflammatory diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA). Since thiols could be potent inhibitors of the production of cytokines, the effects of dimethyl sulphoxide (DMSO) and dimethyl sulphone (DMS) on constitutive and IL-1β-induced IL-6 and IL-8 expression in the human chondrocyte cell line C-28/I2 were evaluated.
MAIN METHODS: C-28/I2 cells were incubated for 12h with different concentrations of DMSO or DMS. The secretion of IL-6 and IL-8 was quantified by enzyme-linked immunosorbent assays (ELISAs). The impact of DMSO and DMS on the regulation of p38 and ERK1/2 mitogen-activated protein kinases (MAPKs) was confirmed by Western blot experiments. Furthermore, C-28/I2 cells were stimulated with IL-1β in the absence or presence of DMSO and DMS and IL-6 and IL-8 expression was quantified by ELISAs and quantitative real-time polymerase chain reaction (qRT-PCR).
KEY FINDINGS: C-28/I2 cells constitutively expressed large quantities of IL-6 and IL-8. Long-term exposure of cells to DMSO (1%) or DMS (100mM) led to a dramatic downregulation of IL-6 and IL-8 expression which was accompanied by the deactivation of ERK1/2. Both substances also blocked IL-1β-induced IL-6 and IL-8 expression.
SIGNIFICANCE: In this study, we demonstrate that both DMSO and DMS represent strong anti-inflammatory properties by blocking constitutive as well as IL-1β-induced IL-6 and IL-8 expression in the human chondrocyte cell line C-28/I2.
Methylsulfonylmethane (MSM), also known as dimethyl sulfone and methyl sulfone, is an organic sulfur-containing compound that occurs naturally in a variety of fruits, vegetables, grains, and animals, including humans. In the present study, we demonstrated the anti-inflammatory effects of MSM in lipopolysaccharide (LPS)-stimulated murine macrophages, RAW264.7 cells. MSM significantly inhibited the release of nitric oxide and prostaglandin E(2) by alleviating the expression of inducible nitric oxide synthase and cyclooxygenase-2 in LPS-stimulated RAW264.7 cells. Furthermore, the levels of interleukin-6 and tumor necrosis factor-alpha were decreased by MSM treatment in cell culture supernatants. Further study indicated that the translocation of the p65 subunit of nuclear factor (NF)-kappaB to the nucleus was inhibited by MSM treatment in LPS-stimulated RAW264.7 cells, in which it helped block degradation of inhibitor of NF-kappaB. In addition, in vivo studies demonstrated that topical administration of MSM at 500-1250 microg/ear resulted in similar inhibitory activities in 12-O-tetradecanoylphorbol 13-acetate-induced mouse ear edema. Collectively, theses results indicate that MSM inhibits LPS-induced release of pro-inflammatory mediators in murine macrophages through downregulation of NF-kappaB signaling.
Dimethyl sulfoxide (DMSO) has been demonstrated to suppress the in vitro microbicidal activity of neutrophils. In addition, this compound has been described as having significant anti-inflammatory activity. These properties have generally been attributed to the effectiveness of this compound as a hydroxyl radical scavenger. However, DMSO can also act as a reductant under certain conditions, yielding its fully oxidized form, dimethyl sulfone (DMSO2, or MSM), as the product. Therefore, we evaluated the ability of these two compounds to interfere with the production of oxidants other than the hydroxl radical by stimulated human neutrophils. In a cell-free assay, DMSO was found to quench the oxidant activity of hypochlorous acid. Neither DMSO nor DMSO2 (MSM) reacted with superoxide, hydrogen peroxide, taurine chloramine, or monochloramine in this system. However, both DMSO and DMSO2 (MSM) significantly suppressed the production of superoxide, hydrogen peroxide, and hypochlorous acid by human neutrophils stimulated with either phorbol myristate acetate or opsonized zymosan. Neutrophil viability was not reduced by either DMSO or DMSO2 (MSM). Inhibition of the oxidative function of stimulated neutrophils by DMSO may provide an alternative explanation for the effects of this compound on the microbicidal activity of neutrophils and as an in vivo anti-inflammatory agent.
The potential genotoxicity of methylsulfonylmethane, a crystalline organic sulfur, derived from chemically modified lignin from plants was evaluated using in vitro and in vivo assays. In the bacterial reverse mutation test using Salmonella typhimurium TA98. TA 100, TA 153 5, and TA 1538, methylsulfonylmethane did not induce any significant increase of His' revertants. In the in vitro chromosome aberration test using Chinese Hamster Lung (CHL) cells, no aberration effects were seen. In the in vivo evaluation using a micronucleus test, negative results were obtained. Accordingly, the results indicated that methylsulfonylmethane is not genotoxic and its use is unlikely to present a potential hazard.
Purpose: Osteoarthritis (OA) is a joint disease characterized by a degenerative change of articular cartilage and underlying subchondral bone and often accompanied by inflammation. MSM, a dietary supplement composed of about 34% sulfur and self-affirmed as GRAS (generally recognized as safe) in the U.S., is most utilized for treating OA. A recent study by Kim et. al., OA & Cart, 2006, showed clinical effectiveness of MSM supplementation at 3 gm BID x 12 weeks compared to placebo. The objective of our study was to examine the effect of MSM at varying concentrations on cultured human healthy and osteoarthritic chondrocytes in vitro with a focus on catabolic and anabolic markers.
Methods: Human cartilage tissues were obtained from 22 knees, 72 hrs postmortem from donors with different grades of OA. We used the Outerbridge classification (Grades I - IV), Grade I for intact surface; Grade II for minimal fibrillation; Grade III for overt fibrillation; and Grade IV for erosion of the articular cartilage surface. Following gross assessment of the donor knees, the following knees were studied for Grade I (n=6) (aged 23-38); Grade II (n=9) (aged 50-77); for Grade III (n=5) (aged 32-70); and Grade IV (n=2) (aged 70-93). Cartilage tissues were harvested from femoral condyles and tibial plateaus, the matrix was dissolved with collagenase; the chondrocytes were then cultured for 2 weeks in culture media without MSM. After reaching confluence, 2 x 105 chondrocyte cells in 10 ml culture medium with varying concentrations of MSM (0, 1, 3, 6, 12, and 60 μg/ml) were cultured in 100 mm (in-diameter) plates at 37 °C in 5% CO2 for 3 days. The concentrations were estimated to correspond to human, oral dosing at between 0 and 30 grams of MSM per day. mRNA expression of various markers by RT-PCR including: TNF-alpha, IL-1, MMP-1, MMP-3, and MMP-13 was also determined for each OA grade and each concentration of MSM or control. Anabolic pathways examined included proteoglycan synthesis (by a pulse chase analysis of 35SO4 incorporation) and chondrocyte mRNA expressions of Type-II collagen and aggrecan. A one-way ANOVA was performed to establish the level of statistical significance. Results: In Grade II OA chondrocytes treated with MSM at the concentration of 12 μg/ml, there was a strong trend for MSM to reduce the mRNA expression of inflammatory markers: TNF-alpha (-33%, p=0.08) and IL-1 (-29%, p=0.08) when compared to lower concentrations of MSM and control. These results did not apply for OA chondrocytes of Grade III or IV. MSM did not show an increase in proteoglycan synthesis in cultured chondrocytes or an increase of cartilage matrix production in normal and osteoarthritic chondrocytes at the mRNA level.
Conclusion: MSM might have an ability to protect articular cartilage in early OA by reducing expression of inflammatory cytokines, i.e. TNF-alpha & IL-1. The effective concentration of 12 μg/ml MSM correlates with the dosage used in a recent clinical trial. MSM did not elicit an anabolic response in this study.