Glucuronoxylomannan intranasal challenge prior to Cryptococcus neoformans pulmonary infection enhances cerebral cryptococcosis in rodents

The encapsulated fungus Cryptococcus neoformans is the most common cause of fungal meningitis, with the highest rate of disease in patients with AIDS or immunosuppression. This microbe enters the human body via inhalation of infectious particles. C. neoformans capsular polysaccharide, in which the major component is glucuronoxylomannan (GXM), extensively accumulates in tissues and compromises host immune responses. C. neoformans travels from the lungs to the bloodstream and crosses to the brain via transcytosis, paracytosis, or inside of phagocytes using a "Trojan horse" mechanism. The fungus causes life-threatening meningoencephalitis with high mortality rates. Hence, we investigated the impact of intranasal exogenous GXM administration on C. neoformans infection in C57BL/6 mice. GXM enhances cryptococcal pulmonary infection and facilitates fungal systemic dissemination and brain invasion. Pre-challenge of GXM results in detection of the polysaccharide in lungs, serum, and surprisingly brain, the latter likely reached through the nasal cavity. GXM significantly alters endothelial cell tight junction protein expression in vivo, suggesting significant implications for the C. neoformans mechanisms of brain invasion. Using a microtiter transwell system, we showed that GXM disrupts the trans-endothelial electrical resistance, weakening human brain endothelial cell monolayers co-cultured with pericytes, supportive cells of blood vessels/capillaries found in the blood-brain barrier (BBB) to promote C. neoformans BBB penetration. Our findings should be considered in the development of therapeutics to combat the devastating complications of cryptococcosis that results in an estimated ~200,000 deaths worldwide each year.

Abstract 115: Downregulation of Perivascular Adipose Tissue PPAR Gamma in Western Diet-Induced Persistent Vascular Dysfunction in Female Rats

Consumption of a western diet (WD) is a major part of modern life contributing to the epidemic of Metabolic Syndrome (MS), a significant risk factor for cardiovascular disease. Recent studies from our laboratory have characterized a model of WD induced MS in female rats. Adopting a healthier diet may be sufficient to reverse the constellation of metabolic symptoms associated with MS including obesity-related hypertension. However, it remains unclear if returning to a normal diet overcomes cardiovascular dysfunction associated with MS. We hypothesized that cardiovascular dysfunction will persist despite diet reversal due to altered PPAR-γ, an important vascular tone regulator, in the perivascular adipose tissue (PVAT). Eight-week old female Wistar rats were fed a WD (21% fat, 50% carbohydrate (34% sucrose) for 20 weeks (WD group) to induce MS. Then, the rats were subjected to diet reversal for 8 weeks (rWD group). The control group received a regular chow diet (5% fat, 48.7% carbohydrate (3.2% sucrose). WD group exhibited increased body weight, triglyceride levels, intolerance to glucose and systolic blood pressure characterizing MS. Direct measurement of blood pressure via right carotid catheterization showed that WD increased systolic blood pressure (141.61 ± 10 vs. 119.52 ± 9 mmHg) compared with controls. Strikingly, diet reversal was unable to drop systolic blood pressure (139.87 ± 13 mmHg). WD impaired acetylcholine and sodium nitroprusside-mediated relaxation in aortic rings. These effects remained unchanged even after diet reversal. Expression of PPAR-γ in aortic PVAT was significantly reduced in the WD group (3.2 fold) and in the rWD group (2.4 fold ) compared with controls. Moreover, we found high levels of lysine acetylation in the PVAT from WD (2.8 fold ) and rWD group (2.0 fold) compared with controls. Despite reversal WD led to significant improvement of all metabolic parameters, including weight loss, this strategy was unable to reverse vascular dysfunction and elevated blood pressure caused by WD consumption. Decreased PPAR-γ expression in PVAT associated with hyperacetylation will be further examined as a potential mechanism underlying persistent vascular dysfunction in WD-induced MS.

Abstract P139: Ft3 Level Correlates with Arterial Stiffness and Systolic Blood Pressure: A Cross-sectional Study

Background: Previous studies have suggested that thyroid dysfunction was associated with numerous risk factors of cardiovascular diseases, but whether thyroid function status could influence arterial stiffness and blood pressure (BP) has not been investigated sufficiently.

Methods: From January to December 2011, we enrolled 1732 patients who took physical examination in our center consecutively. The exclusion criteria were: previous histories of cardiovascular and cerebrovascular diseases, current usage of any anti-hypertensive drugs, anti-thyroid drugs, or thyroxin. All patients underwent testing for thyroid function status, brachial-ankle pulse wave velocity (baPWV), and ankle brachial index (ABI). We investigated the relationship between thyroid hormone levels, arterial stiffness markers (baPWV and ABI) and BP.

Results: There were 97 patients (5.6%) who had thyroid dysfunction, including low-T3-syndrome (11 patients, 0.64%), subclinical hypothyroidism (51 patients, 2.94%) and clinical hypothyroidism (19 patients, 1.10%), subclinical hyperthyroidism (16 patients, 0.92%). After adjusting for conventional risk factors (age, gender, smoking, diabetes mellitus, dyslipidemia, previous hypertension), free triiodothyronine (FT3) was negatively correlated with baPWV (r=-0.482, P<0.001) and positively correlated with ABI (r=0.290, P<0.001), indicating that the lower FT3 level correlates with arterial stiffening. FT3 also had a moderate negative correlation with systolic BP (r=-0.375, P<0.001). TSH was significantly associated with baPWV (r=0.327, P=0.002), but it did not have any relationship with ABI and BP. No significant correlation was found between other thyroid hormone levels (TT4, FT4 and TT3), baPWV, ABI and BP.

Conclusions: Lower FT3 and higher TSH were associated with arterial stiffening markers. In addition, FT3 is negatively correlated with systolic BP. These results indicate that thyroid hormone levels play an important role in arterial stiffness and hypertension. Further study is warranted to investigate whether thyroid hormone therapy could benefit people with arterial stiffening and hypertension.