Serotonin fails to induce proliferation of endothelial cells preloaded with eicosapentaenoic acid and docosahexaenoic acid

9-trans, 11-trans-CLA: antiproliferative and proapoptotic effects on bovine endothelial cells

Endothelial cell function can be influenced by nutrition, especially dietary FA and antioxidants. One class of dietary FA that is found in meat and dairy products derived from ruminant animals is conjugated linoleic acids (CLA). We have examined the effects of several CLA isomers on endothelial cell proliferation. 9t,11t-CLA was the only isomer that inhibited bovine aortic endothelial cell (BAEC) [3H]methylthymidine incorporation (I50 = 35 microM), and this antiproliferative effect was time-dependent. A small decrease (20%) in cell number was observed only at the highest concentration (60 microM) tested. The 9c,11t-, 9c,11c-, 10t 12c-, and 11c,13t-CLA isomers did not exhibit any antiproliferative effects over a 5-60 microM concentration range. alpha-Tocopherol and BHT decreased BAEC proliferation, but pretreatment of cells with either of these antioxidants substantially attenuated the antiproliferative effect of 9t,11 t-CLA. No difference in lipid peroxidation, as measured by the thiobarbituric acid assay for malondialdehyde, was observed on treatment of endothelial cells with either 9t,11 t- or 9c,11 t-CLA. However, a 43% increase in caspase-3 activity was observed after incubating BAEC with 9t,11 t-CLA, suggesting that the antiproliferative effect of this isomer is partially due to an apoptotic pathway. In contrast to the above results with normal endothelial cells, these five CLA isomers all inhibited proliferation of the human leukemic cell line THP-1, with the 9t,11 t isomer again being the most (I50 = 60 microM) effective. These results confirm that different CLA isomers have different inhibitory potencies on the proliferation of normal and leukemic cells.

The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina

In this work we advance the hypothesis that omega-3 (omega-3) long-chain polyunsaturated fatty acids (LCPUFAs) exhibit cytoprotective and cytotherapeutic actions contributing to a number of anti-angiogenic and neuroprotective mechanisms within the retina. omega-3 LCPUFAs may modulate metabolic processes and attenuate effects of environmental exposures that activate molecules implicated in pathogenesis of vasoproliferative and neurodegenerative retinal diseases. These processes and exposures include ischemia, chronic light exposure, oxidative stress, inflammation, cellular signaling mechanisms, and aging. A number of bioactive molecules within the retina affect, and are effected by such conditions. These molecules operate within complex systems and include compounds classified as eicosanoids, angiogenic factors, matrix metalloproteinases, reactive oxygen species, cyclic nucleotides, neurotransmitters and neuromodulators, pro-inflammatory and immunoregulatory cytokines, and inflammatory phospholipids. We discuss the relationship of LCPUFAs with these bioactivators and bioactive compounds in the context of three blinding retinal diseases of public health significance that exhibit both vascular and neural pathology. How is omega-3 LCPUFA status related to retinal structure and function? Docosahexaenoic acid (DHA), a major dietary omega-3 LCPUFA, is also a major structural lipid of retinal photoreceptor outer segment membranes. Biophysical and biochemical properties of DHA may affect photoreceptor membrane function by altering permeability, fluidity, thickness, and lipid phase properties. Tissue DHA status affects retinal cell signaling mechanisms involved in phototransduction. DHA may operate in signaling cascades to enhance activation of membrane-bound retinal proteins and may also be involved in rhodopsin regeneration. Tissue DHA insufficiency is associated with alterations in retinal function. Visual processing deficits have been ameliorated with DHA supplementation in some cases. What evidence exists to suggest that LCPUFAs modulate factors and processes implicated in diseases of the vascular and neural retina? Tissue status of LCPUFAs is modifiable by and dependent upon dietary intake. Certain LCPUFAs are selectively accreted and efficiently conserved within the neural retina. On the most basic level, omega-3 LCPUFAs influence retinal cell gene expression, cellular differentiation, and cellular survival. DHA activates a number of nuclear hormone receptors that operate as transcription factors for molecules that modulate reduction-oxidation-sensitive and proinflammatory genes; these include the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and the retinoid X receptor. In the case of PPAR-alpha, this action is thought to prevent endothelial cell dysfunction and vascular remodeling through inhibition of: vascular smooth muscle cell proliferation, inducible nitric oxide synthase production, interleukin-1 induced cyclooxygenase (COX)-2 production, and thrombin-induced endothelin 1 production. Research on model systems demonstrates that omega-3 LCPUFAs also have the capacity to affect production and activation of angiogenic growth factors, arachidonic acid (AA)-based vasoregulatory eicosanoids, and MMPs. Eicosapentaenoic acid (EPA), a substrate for DHA, is the parent fatty acid for a family of eicosanoids that have the potential to affect AA-derived eicosanoids implicated in abnormal retinal neovascularization, vascular permeability, and inflammation. EPA depresses vascular endothelial growth factor (VEGF)-specific tyrosine kinase receptor activation and expression. VEGF plays an essential role in induction of: endothelial cell migration and proliferation, microvascular permeability, endothelial cell release of metalloproteinases and interstitial collagenases, and endothelial cell tube formation. The mechanism of VEGF receptor down-regulation is believed to occur at the tyrosine kinase nuclear factor-kappa B (NFkappaB). NFkappaB is a nuclear transcription factor that up-regulates COX-2 expression, intracellular adhesion molecule, thrombin, and nitric oxide synthase. All four factors are associated with vascular instability. COX-2 drives conversion of AA to a number angiogenic and proinflammatory eicosanoids. Our general conclusion is that there is consistent evidence to suggest that omega-3 LCPUFAs may act in a protective role against ischemia-, light-, oxygen-, inflammatory-, and age-associated pathology of the vascular and neural retina.

Treatment with selective serotonin reuptake inhibitors for enhancing wound healing

Selective serotonin reuptake inhibitors (SSRIs) are well-established medications for the treatment of mood disorders including major depression. These agents are also known to exhibit potent antiplatelet and endothelium protective effects effects. Additionally, SSRIs can exacerbate the development of inflammation, and modulate the interleukin and interferon production. All of the above suggest that SSRIs therapy could be considered as a potential strategy for the wound healing treatment. We summarized some body of the available data on the history of serotonin metabolism, mechanism of action of ketanserin, and hypothesize why SSRIs may be beneficial in the wound repair natural history. Different pathophysiological considerations are also reflected in this review. Finally, we suggest that the topical use of SSRIs may represent a promising avenue for future strategies affecting wound repair in high-risk patients, especially those with diabetes mellitus, venous insufficiency, obesity, and other vascular disorders.

Differential effects of low-dose docosahexaenoic acid and eicosapentaenoic acid on the regulation of mitogenic signaling pathways in mesangial cells

Although dietary fish oil supplementation has been used to prevent the progression of kidney disease in patients with IgA nephropathy, relatively few studies provide a mechanistic rationale for its use. Using an antithymocyte (ATS) model of mesangial proliferative glomerulonephritis, we recently demonstrated that fish oil inhibits mesangial cell (MC) activation and proliferation, reduces proteinuria, and decreases histologic evidence of glomerular damage. We therefore sought to define potential mechanisms underlying the antiproliferative effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the predominant omega-3 polyunsaturated fatty acids found in fish oil, in cultured MC. DHA and EPA were administered to MC as bovine serum albumin fatty-acid complexes. Low-dose (10-50 micromol/L) DHA, but not EPA, inhibited basal and epidermal growth factor (EGF)-stimulated [(3)H]-thymidine incorporation in MCs. At higher doses (100 micromol/L), EPA and DHA were equally effective in suppressing basal and EGF-stimulated MC mitogenesis. Low-dose DHA, but not EPA, decreased ERK activation by 30% (P <.01), as assessed with Western-blot analysis using phosphospecific antibodies. JNK activity was increased by low-dose DHA but not by EPA. p38 activity was not significantly altered by DHA or EPA. Cyclin E activity, as assessed with a histone H1 kinase assay, was inhibited by low-dose DHA but not by EPA. DHA increased expression of the cell cycle inhibitor p21 but not p27; EPA had no effect on p21 or p27. We propose that the differential effect of low-dose DHA vs EPA in suppressing MC mitogenesis is related to down-regulation of ERK and cyclin E activity and to induction of p21.

Serotonin and the heart

Serotonin is a naturally occurring vasoactive substance that has diverse cardiophysiological effects. These effects can be explained by the existence of serotonin receptor subtypes which mediate different biological actions. The vasoconstrictive actions of serotonin are mediated by 5-HT2 serotonergic receptors, and serotonin also amplifies the release and activities of other vasoconstrictors, such as angiotensin and norepinephrine. Abnormalities in the serotonergic system may play an important role in the pathophysiology of multiple cardiovascular disease states such as systemic hypertension, primary pulmonary hypertension and peripheral vascular disease. Selective 5-HT2 serotonergic receptor blockers have been developed which appear to be potent vasodilators with therapeutic potential in various cardiovascular disease states. The largest clinical experience has been collected with ketanserin, and other agents in this class are being investigated. Prolongation of the ECG QT interval with 5-HT2 serotonergic receptor blockers may pose a potential risk with these treatments in some patients.