These results suggest that blueberry components may support angiogenesis under normal physiological conditions, but attenuate abnormal angiogenesis induced by overactive growth factors. Blueberries exert protective effects on endothelial models by reducing oxidative stress and monocyte adhesion to the endothelium and modulating angiogenesis. The direct impact of blueberry compounds on endothelial dysfunctionin vivo remains to be elucidated, with few studies focusing on the molecular pathways involved in atherosclerosis.Inflammation in the brain can be generated by the dysregulation of inflammatory pathways, molecular signals released by injured neurons, or the accumulation of protein aggregates . Brain inflammation has been associated with an impairment of neuron regeneration and an increase in the incidence of neurodegenerative diseases such as multiple sclerosis , and Alzheimer’s and Parkinson’s diseases . Mechanisms involved in neurodegeneration have been reviewed in detail by Jellinger . The sensitivity of brain muscarinic receptors to oxidative stress increases with aging , and abnormal signaling is implicated in neurodegenerative diseases. Blueberry extracts alleviate oxidative stress in neuronal models through a variety of mechanisms , including scavenging of ROS and downregulation of iNOS gene expression . In COS-7 cells transfected with muscarinic receptors, treatment with a whole blueberry extract reduced activation of the cAMP response element-binding pathway, which can be activated by protein aggregates and is involved in oxidative stress in neurons . Several blueberry fractions exerted antioxidant effects,black plastic plant pots although via different mechanisms: a blueberry extract polar fraction and a nonpolar fraction both reduced oxidative stress in TNF-α– and PMA-induced human neuroblastoma . The polyphenolic-rich fraction exerted scavenging activity of ROS, whereas the nonpolar fraction disrupted NOX assembly, a mechanism that generates the production of ROS.
Blueberry treatment also reduced proinflammatory cytokines in LPS-induced BV-2 cells, through modulation of COX-2 gene expression and the inhibition of NF-κB translocation into the nucleus . The phenolic extracts increased concentrations of Arg-1 , a marker of the M2 phenotype of macrophages, which promotes a return to homeostasis necessary to avoid chronic inflammation. In a model of microglial cells subjected to inflammation in different glycemic conditions, a blueberry extract was effective at inhibiting inflammatory markers, with a comparable effect to the insulin treatment used in the model . Protein aggregations in the brain result from the abnormal deposition of misfolded proteins, leading to the accumulation of fibrils, including α-synuclein or amyloid-βinto plaques . Accumulation of Aβ aggregates is associated with impairment of normal physiological activity of the neurons, increased production of ROS , and activation of microglia and astrocytes . Immune cells also generate Aβ , therefore upregulating the inflammatory cascade. A blueberry extract and an anthocyanin fraction conferred protection against protein aggregate-induced cytotoxicity in mouse neuroblastoma and rat hippocampal neurons challenged with Aβ species , most likely through the inhibition of the CREB pathway but with no effect on ERK activation . αSyn-challenged mouse microglia were also protected by polyphenol extracts, but not the cells challenged with glutamate, which is sometimes found in excess in pathological conditions . Based on results in cell models, it is possible that the active compounds of blueberries could dampen the development of neurodegenerative diseases by reducing oxidative stress and inflammation, which limits the formation of protein aggregates and associated cell damage.
It is important to remember that although cell culture studies of neurons and glial cells provide useful information to understand inflammation mechanisms in the brain, these models may be oversimplified due to the lack of a blood-brain barrier, which is critical in maintaining homeostasis .The skin is subjected to constant challenge, including pollution, physical damage , and light irradiation, that play a role in the initiation of inflammation . Cell models include keratinocytes, found in the epidermis , and fibroblasts that synthesize the extracellular matrix, used alone or in coculture . Recently, 3D skin models and a human skin equivalent have been developed to provide more complex models for testing toxicity, absorption, and metabolism with the presence of several epidermal layers and stratum corneum . Blueberry extracts were used to treat human keratinocytes and a human skin model challenged with O3 exposure, a toxic pollutant that can alter the redox status of the skin and induce inflammation . O3 impaired wound healing of the cells, but function was recovered with a blueberry polyphenol treatment by activating cellular antioxidant defense systems, reducing H2O2 production . A blueberry polyphenol extract was compared with 2 anthocyanin and proanthocyanidin-rich extracts to investigate wound healing in human fibroblasts , and anti-inflammatory and antioxidant effects on murine macrophages. The fractions were both effective at reducing ROS production and alleviated inflammation by reducing the expression of COX-2 and iNOS in the macrophages, but the protective effects of proanthocyanidins were more pronounced than for the other blueberry polyphenols . Blueberry treatments, obtained through several extraction methods, were also effective at reducing NO production of human foreskin fibroblast induced by IL-2β . The major risk factor for developing skin cancer is sun exposure. DNA absorbs UV-B, which can induce the formation of dimeric pyrimidine bases . These mutations are usually repaired by nucleotide excision, although certain mutations, notably in the p53 gene, result in the loss of this repair function , possibly leading to the development of squamous or basal cell carcinoma .
In cells exposed to UV-B, responsible for DNA damage and initiation of proinflammatory pathways, a blueberry extract protected DNA against strand break formation . Blueberry extracts also demonstrated anti-inflammatory effects in UVB-challenged cells and reduced cytokine gene expression through inhibition of NF-κB and MAPK activations . UV-A, in contrast, is less absorbed by DNA, but can interact with exogenous chromophores and induce lipid peroxidation, which generates ROS . These reactive species can lead to the oxidation of nucleic acid, DNA strand breaks , and increased MMP-1 activity , potentially increasing the risk of aggressive cancer. The increase of oxidative stress by UV-A on keratinocytes was partially reduced by a blueberry phenolic extract through decreased ROS production and lipid peroxidation . The third type of sunlight irradiation, UV-C, has the weakest penetration rate in the atmosphere, but has very high energy, possibly contributing to oxidative stress, inflammation, and DNA damage in the skin cells. A blueberry extract applied to HaCaT keratinocytes and HFF fibroblasts irradiated with UV-C showed protective effects against oxidative stress and DNA damage. The anti-inflammatory effects of the treatment were, however, only characterized in the keratinocyte and fibroblast coculture and the activation of MMP-1 expression by fibroblasts after irradiation was only observed in the presence of keratinocytes, suggesting interactions between the 2 types of cells . These observations support the need to use more complex models to investigate mechanisms mediated by the interaction between cell types in the skin. Limiting the studies to one type of cell may leave out crucial information regarding the physiological effects of the treatments on the skin. The results to date in cell models suggest that blueberry derivatives could have a protective effect on skin damage in response to sun and other stressors; however, the extent to which these molecules are stored and present in skin cells or associated tissue layers in vivo is not clear.Artificial lights, environment, diet deficiencies, pathologies, and aging can impact oxidative stress and inflammation in the eyes, and may contribute to diabetic retinopathy or age-related macular degeneration . The eye tissues and fluids contain little extracellular SOD, hence they have less protection against superoxide radical damage . Despite having higher SOD activity, the retina is at more risk of oxidative stress due to its high content of unsaturated fatty acids and high exposure to light leading to lipid peroxidation, which can, in turn, react with DNA, proteins, and lipids, inducing cell damage . Studies on blueberry compounds applied to cell-based models relevant to eye function have typically used light irradiation , a chemical challenge ,black plastic planting pots or a combination of both to induce inflammation . The protective effect of blueberry compounds on oxidative stress induced by light in ocular models has been tentatively explained through a decrease in ROS production and lipid peroxidation. In murine photoreceptors induced with UV and blue light, blueberry extracts exerted protective effects through regulation of ROS production, limiting cell death induced by the light through inhibition of p38-MAPK, JNK, and NF-κB pathways . The effects of blueberry extracts on alternatively challenged cells were also reported , but more research is needed to confirm the mechanisms behind their antioxidant and anti-inflammatory effects. Oxidative stress was alleviated by blueberry compounds in chemically challenged retinal pigment epithelial cells through an increased production of antioxidant enzymes . Blueberry anthocyanins modulated oxidative stress through a decrease in ROS production and increase in glutathione peroxidase activity in ARPE-19 cells induced with H2O2 . In 661 W cells challenged with high glucose, anthocyanins reduced ROS secretion and NOX protein expression, but limited anti-inflammatory effects were reported with no clear modulation of NF-κB .
Blueberry anthocyanins tested on light-induced ARPE-19 cells helped mitigate lipid peroxidation , whereas malvidin 3-glucoside, purified from a blueberry extract, decreased ROS and VEGF production in irradiated cells . However, a blueberry flavonoid fraction and whole polyphenol mixture were more effective than the anthocyanin and phenolic acid fractions at reducing lipid peroxidation . These observations support the evidence for a general effect to reduce cell stress markers in ocular cell models when using multiple blueberry fractions and phytochemicals, with a potentially stronger activity of the total polyphenol extracts as opposed to individual compounds. Thus, testing the effects of dietary blueberries or their derivatives on eye function is an interesting avenue for future research.Inflammatory bowel diseases encompass chronic inflammation-related disorders in the gastrointestinal tract. Chronic inflammation, associated with oxidative stress, increases the risk of developing colorectal cancers . Even though genetic predispositions have been documented , environmental factors such as the gut microbiota composition, influenced by lifestyle and diet, and its interaction with the intestinal mucosa, are key factors in increasing the prevalence of IBD . The effects of blueberry compounds on intestinal models are reported in Table 7, along with experimental conditions. IBDs are characterized by a loss of intestinal barrier integrity through the alteration of tight junction proteins . Although it is not clear if this loss of permeability is a cause or consequence of IBD, it promotes the chance of pathogens to enter the mucosa, triggering inflammation . Blueberry extracts were tested on Caco-2 cell permeability using a transepithelial electrical resistance measurement. The anthocyanin and total polyphenolic fractions decreased permeability of the cell monolayer induced by Escherichia coli challenge, but the proanthocyanidin fraction did not restore TEER values. The authors suggested an interaction between proanthocyanidins, cell surface proteins, and the ability of E. coli to adhere to the cells . Regarding oxidative and inflammatory markers, a number of cytokine gene expressions have been found to increase in colonic mucosa of ulcerative colitis patients due to excessive immune response and immune cell reactivity . In T84 cells, the increase in TNF-α and IP-10 gene expressions by a cytokine cocktail were counteracted by a blueberry extract and the production of IL-8 protein was slightly, but not significantly inhibited . ROS production in a similar cell model was also decreased by blueberry compounds . However, the effects of blueberry compounds on the NF-κB pathway remain unclear, with contradictory effects reported in intestinal models of inflammation. The response induced by cytokines was dose-dependently alleviated by a blueberry anthocyanin fraction in Caco-2 cells through the inactivation of NF-κB, but a water extract from the same fruits did not modulate the inflammatory response . An anthocyanin extract used on T84 human colon cells decreased the activation of the STAT pathway, upregulated during IBD, but also upregulated the NF-κB pathway . A strong advantage of using an intestinal model is the possibility to study both the effect of polyphenol compounds and their colonic metabolites in a more physiologically relevant situation than for other systems in the body, as both parent molecules and metabolites are present in the intestinal epithelial cell environment despite the low bio-availability of polyphenolic compounds. The limited number of studies on blueberry phytochemicals and cell culture models of intestinal inflammation, the diversity of cell lines used, and parameters measured speak to the need for more studies to determine how blueberries modulate gut function and health.Because both inflammation and oxidative stress are frequently associated with the development of chronic diseases , it is important to understand how dietary factors impact these outcomes. Here, we have reviewed studies reporting the effects of blueberry phytochemicals on cell culture models of inflammation and/or oxidative stress .