25 research outputs found
11β-hydroxysteroid dehydrogenase type I inhibition in solid tumours
Glucocorticoids, key hormonal regulators of the stress response, powerfully influence
inflammation and metabolism. Reducing excessive glucocorticoid exposure is
beneficial in treating metabolic and cognitive disorders, but manipulating systemic
endogenous glucocorticoids risks compromising their beneficial effects. The enzyme
11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activates glucocorticoids in
target tissues and thus inhibition of this enzyme presents a clinical opportunity to
reduce tissue-specific glucocorticoid action. Active glucocorticoids also exert potent
angiostatic effects by binding the glucocorticoid receptor (GR), and 11β-HSD1
inhibitors have proven beneficial in models of myocardial infarction by promoting
angiogenesis. The possibility that 11β-HSD1 inhibitors may increase pathological
angiogenesis, such as that seen in solid tumours, remains unaddressed. This project
tested the hypothesis that 11β-HSD1 inhibition promotes tumour growth as a result of
increased angiogenesis, using murine models of squamous cell carcinoma (SCC) and
pancreatic ductal adenocarcinoma (PDAC).
Murine SCC or PDAC cells were injected (1x106 cells/flank) into WT female mice fed
either standard diet, or diet containing the 11β-HSD1 inhibitor UE2316 (175 mg/kg,
N=6/group), or into 11β-HSD1 knockout (Del1) mice fed standard diet. Developing
tumours were measured by callipers over several weeks, before animals were culled
and tissues collected. SCC tumours grew more rapidly in UE2316-treated mice to
reach a significantly (P<0.01) larger final volume (0.158 ± 0.037 cm3) than in control
mice (0.051 ± 0.007 cm3). PDA tumours were unaffected by 11β-HSD1 inhibition or
deletion. Immunofluorescent co-staining of tumour sections for CD31/α-smooth
muscle actin revealed no differences in vessel density, and RT-qPCR showed no
difference in angiogenic factor expression, after 11β-HSD1 inhibition/deletion in
either tumour type. GR and 11β-HSD1 RNA expression were greater in SCC vs PDAC
tumours (P<0.001), as was 11β-HSD1 activity (P<0.0001).
In studies using the aortic ring assay of ex vivo angiogenesis, 11β-HSD1 deletion, but
not inhibition with UE2316, was shown to prevent glucocorticoid-mediated
angiostasis. The growth/viability of tumour cell lines was not affected by UE2316 or
corticosterone, as assessed by live cell imaging using the Incucyte imaging system.
RNA-sequencing of SCC tumours revealed that multiple factors involved in the innate
immune/inflammatory response were reduced in UE2316-treated tumours, and that
extracellular matrix regulation was also altered by UE2316. Imaging of tumour
sections using Second Harmonic Generation microscopy confirmed that UE2316
altered Type I collagen deposition in SCC (P<0.001) but not PDAC.
11β-HSD1 inhibition can increase tumour growth, possibly via suppression of
inflammatory/immune cell signalling and alteration of the extracellular matrix, and
tumours with higher GR and 11β-HSD1 content, such as SCC, may be more at risk.
Interestingly this investigation found no evidence of increased angiogenesis in vivo or
ex vivo after UE2316 treatment, suggesting that 11β-HSD1 inhibition does not
promote angiogenesis in all ischaemic environments. Future work must focus on the
effects of 11β-HSD1 inhibition on the immune and extracellular matrix component of
the tumour microenvironment. While promotion of pathological angiogenesis does not
appear to pose a major threat, 11β-HSD1 inhibitors may still interact with the immune
and inflammatory environment in tumours to the detriment of health
Endostatin modulates VEGF-mediated barrier dysfunction in the retinal microvascular endothelium
Recent evidence indicates that the anti-angiogenic peptide endostatin may modulate some of the vasomodulatory effects of vascular endothelial growth factor (VEGF) in the retina, including reduction of blood retinal barrier function although it remains uncertain how endostatin promotes endothelial barrier properties. The current study has sought to examine how physiological levels of endostatin alters VEGF-induced inner BRB function using an in vitro model system and evaluation of occludin and ZO-1 regulatory responses. In addition, the ability of exogenous endostatin to regulate VEGF-mediated retinal vascular permeability in vivo was investigated. Retinal microvascular endothelial cells (RMEC's) were exposed to various concentrations of endostatin. In parallel studies, RMEC monolayers were treated with vascular endothelial growth factor (VEGF₁₆₅). Vasopermeability of RMEC monolayers and occludin expression were determined. Blood retinal barrier integrity was quantified in mouse retina using Evans Blue assay following intravitreal delivery of VEGF₁₆₅, endostatin or a VEGF/endostatin combination. Endostatin increased the levels of expression of occludin whilst causing no significant change in FITC-dextran flux across the RMEC monolayer. Endostatin reversed the effects of VEGF₁₆₅-enhanced permeability between microvascular endothelial cells and induced phosphorylation of occludin. Evans Blue leakage from retinas treated with VEGF was 2.0 fold higher than that of contra-lateral untreated eyes (P<0.05) while leakage of eyes from endostatin treated animals was unchanged. When eyes were injected with a combination of VEGF₁₆₅ and endostatin there was a significant reduction in retinal vasopermeability when compared to VEGF-injected eyes (P<0.05). We conclude that endostatin can promote integrity of the retinal endothelial barrier, possibly by preventing VEGF-mediated alteration of tight junction integrity. This suggests that endostatin may be of clinical benefit in ocular disorders where significant retinal vasopermeability changes are present.10 page(s
Common pathways in dementia and diabetic retinopathy: understanding the mechanisms of diabetes-related cognitive decline.
Type 2 diabetes (T2D) is associated with multiple comorbidities, including diabetic retinopathy (DR) and cognitive decline, and T2D patients have a significantly higher risk of developing Alzheimer's disease (AD). Both DR and AD are characterized by a number of pathological mechanisms that coalesce around the neurovascular unit, including neuroinflammation and degeneration, vascular degeneration, and glial activation. Chronic hyperglycemia and insulin resistance also play a significant role, leading to activation of pathological mechanisms such as increased oxidative stress and the accumulation of advanced glycation end-products (AGEs). Understanding these common pathways and the degree to which they occur simultaneously in the brain and retina during diabetes will provide avenues to identify T2D patients at risk of cognitive decline