It is well described that MMP-9 increases blood brain barrier permeability and increases ischaemia-induced damage during acute stroke (Cunningham et al., 2005; Jian Liu and Rosenberg, 2005).
Altered neurovascular functions in PD can lead to increased blood-brain barrier permeability and increased peripheral neutrophil and monocyte infiltration into the SN region, where they play an important role in neuroinflammation [ 9] and DA neuronal death.
Whether activation of stress response pathways relates to apoptosis, brain blood barrier permeability, or increased cancer in humans remains to be investigated.
A previous study showed that IGF-1 reduced intestinal barrier permeability through increasing COX-2 expression and decreasing TNF-alpha expression of enterocytes [ 6].
Consequently, a given augmentation in hydrostatic pressure will trigger a greater augmentation in fluid efflux if alveolocapillary barrier permeability is increased.
A previous study showed that IGF-1 reduced intestinal barrier permeability through increasing cyclooxygenase-2 (COX-2) expression and decreasing tumor necrosis-alpha (TNF-alpha) expression of intestinal cells [ 6].
In patients suffering from acute respiratory distress syndrome (ARDS), the alveolar-capillary barrier permeability is increased due to inflammation, resulting in extravasation of protein-enriched fluid into the alveoli [ 1].
This speculation is consistent with the finding that the blood-brain barrier permeability is increased up to 22%% in and around brain tumor compared with normal brain tissue [ 24, 25].
Reduced expression of Tjp1 increases barrier permeability and downregulation of Aqp1, among other factors, has been proposed to contribute to edema development in a rat model of branch retinal vein occlusion.
Although alcohol itself does not alter intestinal permeability, one of the products of alcohol metabolism (i.e., acetaldehyde) increases barrier permeability in a dose-dependent manner (Basuroy et al. 2005) by disrupting intercellular connections, including both tight and adherens junctions (Atkinson and Rao 2001).
Serum albumin levels, recovered from BAL fluid, increased following S. pneumoniae infection in both young and aged mice, although there was no difference between the two age groups (Fig. 2 A ), indicating that increased neutrophil influx does not result in increased barrier permeability.
