The study shows that DHA and EPA, individually and at low in vitro concentrations, have the ability to decrease MMP-9 production and activity in PBMC from healthy controls. In addition, both types of omega-3 FA were able to inhibit T cell migration through a fibronectin barrier in a concentration-dependent fashion. Cell viability was checked for all in vitro assays and remained between 68–84% for all concentrations tested, indicating that the effects observed were not a result of cell death.
MMP-9-mediated disruption of the blood brain barrier is one mechanism in which inflammatory cells enter the CNS in MS. MS patients are reported to have significantly elevated MMP-9 mRNA levels when compared to healthy controls. The increased MMP-9 expression in immune cells (PBMC) may enable these cells to more readily migrate across the blood brain barrier and enter the CNS [26
]. Stüve et al. observed that activated T-lymphocytes isolated from untreated MS patients were able to migrate through a fibronectin barrier due to increased MMP-9 activity. T-lymphocytes treated with IFN-beta decreased the migratory ability of these cells [18
]. Dressel et al. observed that the migration of CD4+ T cells through a fibronectin barrier, but not CD8+ cells, was enhanced in untreated MS patients compared with controls and that CD4+ cell migration and MMP-9 production were reduced by IFN-beta treatment [16
]. Decreasing MMP-9 expression and MMP-9 protein levels in T-lymphocytes is one proposed mechanism for the therapeutic action of IFN-beta therapy in MS [17
In the present study, we demonstrated that EPA and DHA were able to decrease MMP-9 protein levels and activity at relatively low concentrations. Incubation of PBMC from healthy controls with DHA and EPA at 50μ
g/mL reduced MMP-9 levels to non-detectable levels and reduced MMP-9 activity by 51% and 69%, respectively. Oleic acid, a monounsaturated fatty acid, served as an oil control and did not significantly decrease MMP-9 level or activity (Figures and ). In addition, EPA at as low as 10μ
g/famL and DHA at 30μ
g/mL significantly inhibited T cell migration through a fibronectin barrier and this inhibition was associated with decreased MMP-9 activity [Figures and ]. Oleic acid did not significantly inhibit T cell migration. These findings indicate that the omega-3 FA, DHA and EPA, have the ability to decrease immune cell secretion of MMP-9 protein and reduce its activity; together, these modulatory effects on MMP-9 may impede cell migration across the basement membrane of the CNS.
levels in plasma are reported at 7.7
mg/dL for EPA and 9.8
mg/dL for DHA after supplementation with fish oil at a daily oral dose of 3.0 grams (containing 0.57 grams EPA and 0.45 grams DHA) [28
]. In the present study, the in vitro concentration of EPA and DHA at 5
g/mL) showed a decrease in MMP-9 levels, activity, and a decrease in T cell migration. The results presented suggest that it may be possible to decrease MMP-9 levels at a dose of omega-3 FA that is one-third of the dose reported to decrease MMP-9 levels in MS subjects [24
]. There are limited studies evaluating the effects of omega-3 FA supplementation in MS and only one study evaluating omega-3 FA effects on MS disease activity. One double-blind placebo-controlled trial that randomized MS patients (n
= 312) to 20 fish oil capsules/day or an olive oil placebo reported a trend in improvement in the fish-oil-treated subjects compared to controls in disease severity (Expanded Disability Status Scale) over 2 years (P
= 0.07) [29
]. The olive oil placebo contained 72% oleic acid, and the fish oil contained EPA 1.71 grams/day and DHA 1.41 grams/day. One study reported a significant decrease from baseline in the levels of the proinflammatory cytokines Interleukin-1beta (IL-1 β
< 0.03), tumor necrosis factor-alpha (TNF-α
< 0.02), IL-2 (P
< 0.002), and IFN-γ
< 0.01), produced from unstimulated and stimulated PBMC of MS subjects and healthy controls supplemented with fish oil [19
]. Our group has reported a decrease in MMP-9 levels from baseline in an open label study of ten relapsing remitting MS patients receiving fish oil concentrate at 8 grams/day (2.9 grams EPA and 1.9 grams DHA) over 3 months. The reduced MMP-9 levels were observed in all ten subjects whether or not they were taking MS disease modifying medication [24
]. Drawing from the limited clinical trial reports, there is some suggestion that omega-3 fatty acids have immunomodulatory properties that may be beneficial in MS. Further exploration on the optimal dosing of omega-3 FA in MS is needed.