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conserved antigenic structures. TLRs are essential in the first stages of detecting infection and triggering host defenses. TLR2 is generally associated with identifying Gram-positive bacteria and Mycobacteria and its function is enhanced by CD14. CD14 is a membrane-associated glycosylphosphatidylinositol-linked protein expressed at the surface of cells. This pattern recognition receptor is especially associated with macrophages. CD14 acts by assisting in the transfer of bacterial ligands from circulation to TLRs. This complex then activates innate host defense mechanisms, such as release of inflammatory cytokines.85 In addition, human data has shown the effects of Spirulina on monocytes and NK cells with the possibility that it may act on monocytes that induce IFN-gamma production in natural killer (NK) cells.86 NK cells execute a major role in the host-rejection of both tumors and virally infected cells.87 NK cells receive a signal before activation, importantly, cytokines, in particular IFNa/^ aids in NK-cell activation.

An important essential fatty acid gamma linolenic acid (GLA) is present in Spirulina. GLA is also found in nuts green and leafy vegetables. This essential fatty acid is said to contain anti-inflammatory properties because of its metabolism to dihomogamma linolenic acid (DGLA).88 DGLA is a competitive inhibitor of 2-series prostaglandins (PGs). PGs are, transient hormone-like chemicals that regulate cellular activities. They are comprised of unsaturated carboxylic acids, consisting of a 20 carbon skeleton that also contains a five member ring. PGs are biochemically synthesized from the fatty acid, arachidonic acid (AA) and executing various actions depending on the series type. PGs fall into 3 series—PG1, PG2, and PG3. Series 1 and 3 execute anti-inflammatory effects as they decrease inflammation, increase oxygen flow, prevent cell aggregation, and decrease pain. Series 2, conversely, have proinflammatory effects. DGLA has also been shown to be a competitive inhibitor of 4-series leukotrienes (LTs). Leukotrienes are synthesized in the cell from AA by 5-lipoxygenase and function to sustain inflammatory reactions. Dietary GLA has the potential to prevent the formation and therefore the negative inflammatory effects of AA. In addition, a DGLA 15-hydroxyl derivative blocks the transformation of AA to LTs. In order to convert GLA to DGLA, instead of AA, nutrients including magnesium, zinc, and vitamins C, B3, and B6 are necessary with the exception of vitamin C all are present in Spirulina. Supplementation with fatty acids to the aged system can be of use in fortifying degenerating cell walls. Another prominent health concern in the aged population is cancer. The Spirulina component calcium spirulan, a sulfated polysaccharide chelating calcium, has shown promising results in studies. In vitro it has shown tumor migration and adhesion inhibition suggesting a therapeutic agent to reduce metastasis of tumor cells.89 Because the aged individual has a compromised immune system, anything that can help defend the body from future viral infections can be useful. Spirulina has been investigated for its anti-viral activity. In one such study investigators isolated intracellular and extracellular polysaccharide fractions from the A. platensis species. These spirulan-like molecules showed pronounced antiviral activity in the absence of cytotoxic effects. There was inhibition of human cytomegalovirus, herpes simplex virus type 1, human herpes virus type 6, and human immunodeficiency virus type 1. Also, cells that were preincubated with the polysaccharide fraction showed lowered expression of the herpes viruses, pointing to inhibiting the entry of this virus. Other viruses were affected at other points of the viral process.90 In addition to these findings, Spirulina extracts have shown antioxidant effects in vitro and in vivo?9 Furthermore, c-phycocyanin found in Spirulina inhibits COX-2, which leads to a reduction in the inflammatory process.91 Both of these findings are quite beneficial in the aged CNS and can help explain the mechanisms of action with in the system.

Neuroprotection from ischemic brain damage is another area where nutritional and herbal approaches may be of benefit as there is much evidence that oxidative stress and inflammation play a role in the neurodegeneration following ischemic injury. One study sought to investigate the potential of Spirulina to protect the CNS before a focal ischemic stroke and reperfusion injury. 92 The experiment involved feeding adult Sprague-Dawley rats a blueberry, spinach or Spirulina enriched diet for 4 weeks before a 60 min right middle cerebral artery occlusion (MCAO) followed by reperfusion. MCAO normally causes a substantial umbra and penumbra owing to multiple causes. Those animals that received the enriched diets showed a significant reduction in the volume of the infarction with Spirulina being the most effective showing a close to 70% reduction in infarct size (Figure 13.2). The rats that received the diets also showed improved motor behavior following the stroke as demonstrated by an increase in locomotor activity after the stroke. There was a reduction in apoptosis as shown by reduced caspase 3 and tunnel in the animals fed Spirulina before stroke. The data from Wang et al. (05) shows that a diet enriched in spriulina can help in the prevention of damage to brain tissue following an ischemic insult.

The neuroprotective effects of Spirulina have also been investigated in models of neurodegenerative disease. In one model of PD the neurotoxin 6-hydroxydopamine (6-OHDA) is injected into the striatum to induce a slowly progressive degeneration of dopamine neurons in the substantia nigra.93 The death of the dopamine neurons is accompanied by an increase in proinflammatory cytokines, in particular TNF-a and can be modulated by altering TNFa levels.94 This also occurs in the brains of PD patients. In the study by Strömberg et al. (05), Fischer 344 rats were given a diet supplemented with either blueberry or Spirulina for 28 days before the 6-OHDA lesion into the dorsal striatum.95 Seven days or 4 weeks following the lesion, rats were euthanized for analysis of the dopamine neurons by immunohistochemistry. Results from this study indicated that the enriched diets led to an increase in recovery from the PD like insult 1 month following the 6-OHDA lesion, but did not prevent the damage from the initial insult when examined 1 week after the lesion. This was measured as the amount of area in the striatum where dopamine terminals were missing (the tyrosine hydroxylase (TH) negative zone (Figure 13.3). This was accompanied by a significant increase in activated microglia that express OX-6- (MHC class II) in the striatum and the globus pallidus at 1 week following the lesion and a reduced number of microglia at the 1 month time point, an event that was opposite of what was observed in the control animals (Figure 13.4). This early, transient increase in OX-6-positive microglia in the diet-treated animals is likely a beneficial action of the response to the injury where the microglia are phagocytocing the damaged tissues and secreting trophic factors and anti-inflammatory cytokines. Later on in the response to injury the microglial response becomes harmful and the blueberry and Spirulina diets reduced this later harmful phase of inflammation thus promoting regeneration of the dopamine nerve terminals back into the damaged striatum.95

FIGURE 13.2 Bar graph demonstrating that pretreatment with either blueberry, spinach or Spirulina enriched diets significantly reduced the cortical infarction induced by middle cerebral artery occlusion/reperfusion. The right middle cerebral artery was ligated for 60 min. Animals were euthanized for TTC staining 48 h after ischemia/reperfusion, this is a marker of mitochon-drial function. Marked infarction in the right cerebral cortex was found in animals receiving the control diet. Pretreatment with blueberry, spinach, or Spirulina significantly reduced the amount of infarction. Bar graph demonstrates that the infracted area was significantly reduced compared with control diet in the blueberry spinach and Spirulina pretreated groups. This was observed when the infracted area was measured using either (a) volume of infracted area, (b) largest infracted area, or (c) number of infracted slides. This data can be seen in full in Reference 92.

FIGURE 13.2 Bar graph demonstrating that pretreatment with either blueberry, spinach or Spirulina enriched diets significantly reduced the cortical infarction induced by middle cerebral artery occlusion/reperfusion. The right middle cerebral artery was ligated for 60 min. Animals were euthanized for TTC staining 48 h after ischemia/reperfusion, this is a marker of mitochon-drial function. Marked infarction in the right cerebral cortex was found in animals receiving the control diet. Pretreatment with blueberry, spinach, or Spirulina significantly reduced the amount of infarction. Bar graph demonstrates that the infracted area was significantly reduced compared with control diet in the blueberry spinach and Spirulina pretreated groups. This was observed when the infracted area was measured using either (a) volume of infracted area, (b) largest infracted area, or (c) number of infracted slides. This data can be seen in full in Reference 92.

TH-negative zone surrounding the injection site

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