In vitro and in vivo models to assess kidney toxicity of environmental carcinogens

The etiology of sporadic kidney cancer in humans is unclear. However, it is known that VHL tumor suppressor gene mutations are found in the majority of human renal tumors, even in the earliest stages, and play an important role in kidney cancer development. Evidence suggests that VHL may be a target for environmental carcinogens such as trichloroethylene (TCE), which is associated with a specific point mutation in the VHL gene. Co-exposures to elevated levels of TCE and inorganic arsenic through groundwater and dietary sources are frequently found in human populations and are thought to cause multiple organ toxicities. We hypothesize that there is a mechanistic link between environmental co-exposures to TCE- and arsenic-induced renal toxicity that can be elucidated using genetically engineered model systems. Here we have generated both an in vitro model system of the TCE-associated VHL mutation in embryonic stem cells, as well as a unique F3 mouse population derived from the cross between FVB/N-Abcb1a/1b-/-, a multi-drug resistant transporter knockout, and CAST/EiJ, a wild-derived strain from a different subspecies of Mus musculus. We have employed these systems to elucidate the genetic and environmental components critical for the development of renal cell carcinoma due to environmental co-exposures to TCE and arsenic

Regulation of KLF4 Turnover Reveals an Unexpected Tissue-Specific Role of pVHL in Tumorigenesis

The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell fate decision, including cell cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue specific tumor suppressor or oncogene. Here we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and show that pVHL depletion in colorectal cancer cells leads to cell cycle arrest concomitant with increased transcription of the KLF4-dependent p21 gene. Finally, immunohistochemical staining revealed elevated pVHL and reduced KLF4 levels in colon cancer tissues. We therefore propose that unexpectedly pVHL, via the degradation of KLF4, is a facilitating factor in colorectal tumorigenesis

Silent cerebral infarcts in patients with atrial fibrillation: Clinical implications of an imaging-adjusted CHA2DS2-VASc score

Background: The CHA2DS2-VASc score does not include silent infarcts on neuroimaging in stroke risk estimation for patients with atrial fibrillation (AF). The inclusion of silent infarcts into CHA2DS2-VASc scoring and its impact on stroke prophylaxis recommendations in patients with AF has not been previously studied. The present study sought to quantify the prevalence of silent infarcts in patients with AF and describe potential changes in management based on magnetic resonance imaging (MRI) findings. Methods: Participants from the Mayo Clinic Study of Aging with AF and brain MRI were included. Silent infarcts were identified. “Standard” CHA2DS2-VASc scores were calculated for each subject based on clinical history alone and “imaging-adjusted” CHA2DS2-VASc scores based on evidence of cerebral infarction on MRI. Standard and imaging-adjusted scores were compared. Results: 147 participants (average age 77, 28% female) were identified with AF, MRI, and no clinical history of stroke. Overall, 41 (28%) patients had silent infarcts on MRI, corresponding with a 2-point increase in CHA2DS2-VASc score. Of these participants, only 39% (16/41) with silent infarct were on anticoagulation despite that standard CHA2DS2-VASc scores supportive of anticoagulation. After incorporating silent infarcts, 13% (19/147) would have an indication for periprocedural bridging compared to 0.6% (1/147) at baseline. Conclusions: Incorporation of silent infarcts into the CHA2DS2-VASc score may change the risk-benefit ratio of anticoagulation. It may also increase the number of patients who would benefit from periprocedural bridging. Future research should examine whether an anticoagulation strategy based on imaging-adjusted CHA2DS2-VASc scores could result in a greater reduction of stroke and cognitive decline

Regulation of KLF4 Turnover Reveals an Unexpected Tissue-Specific Role of pVHL in Tumorigenesis

The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell fate decision, including cell cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue specific tumor suppressor or oncogene. Here we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and show that pVHL depletion in colorectal cancer cells leads to cell cycle arrest concomitant with increased transcription of the KLF4-dependent p21 gene. Finally, immunohistochemical staining revealed elevated pVHL and reduced KLF4 levels in colon cancer tissues. We therefore propose that unexpectedly pVHL, via the degradation of KLF4, is a facilitating factor in colorectal tumorigenesis

Race and sex effects on the association between muscle strength, soft tissue, and bone mineral density in healthy elders: The Health, Aging, and Body Composition Study

Two factors generally reported to influence bone density are body composition and muscle strength. However, it is unclear if these relationships are consistent across race and sex, especially in older persons. If differences do exist by race and/or sex, then strategies to maintain bone mass or minimize bone loss in older adults may need to be modified accordingly. Therefore, we examined the independent effects of bone mineral-free lean mass (LM), fat mass (FM), and muscle strength on regional and whole body bone mineral density (BMD) in a cohort of 2619 well-functioning older adults participating in the Health, Aging, and Body Composition (Health ABC) Study with complete measures. Participants included 738 white women, 599 black women, 827 white men, and 455 black men aged 70-79 years. BMD (g/cm(2)) of the femoral neck, whole body, upper and lower limb, and whole body and upper limb bone mineral-free LM and FM was assessed by dual-energy X-ray absorptiometry (DXA). Handgrip strength and knee extensor torque were determined by dynamometry. In analyses stratified by race and sex and adjusted for a number of confounders, LM was a significant (p < 0.001) determinant of BMD, except in white women for the lower limb and whole body. In women, FM also was an independent contributor to BMD at the femoral neck, and both PM and muscle strength contributed to limb BMD. The following were the respective Beta-weights (regression coefficients for standardized data, Std beta) and percent difference in BMD per unit (7.5 kg) LM: femoral neck, 0.202-0.386 and 4.7-6.9 %; lower limb,.0.209-0.357 and 2.9-3.5%; whole body, 0.239-0.484 and 3.0-4.7 %; and upper limb (unit = 0.5 kg), 0.231-0.407 and 3.1-3.4%. Adjusting for bone size (bone mineral apparent density [BMAD]) or body size BMD/height) diminished the importance of LM, and the contributory effect of FM became more pronounced. These results indicate that LM and FM were associated with bone mineral depending on the bone site and bone index used. Where differences did occur, they were primarily by sex not race. To preserve BMD, maintaining or increasing LM in the elderly would appear to be an appropriate strategy, regardless of race or sex

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline