Faculty Bibliography

Baboons regularly drink surface waters derived from atmospheric precipitation, or meteoric water. As a result, the oxygen isotope (delta(18)O) composition of their tissues is expected to reflect that of local meteoric waters. Animal proxies of the oxygen isotope composition of meteoric water have practical applications as paleoenvironmental recorders because they can be used to infer aridity and temperature in historic and fossil systems. To explore this premise, we measured the delta(18)O values of hair from two baboon species, Papio anubis and Papio hamadryas, inhabiting Awash National Park, Ethiopia. The hybridizing taxa differ in their ranging behavior and physiological response to heat. Papio hamadryas ranges more widely in the arid thornbush and is inferred to ingest a greater proportion of leaf water that is enriched in (18)O as a result of evaporative fractionation. It is also better able to conserve body water, which reduces its dependence on meteoric waters depleted in (18)O. Taken together, these factors would predict relatively higher delta(18)O values in the hair (delta(18)O(hair)) of P. hamadryas. We found that the delta(18)O(hair) values of P. hamadryas were higher than those of P. anubis, yet the magnitude of the difference was marginal. We attribute this result to a common source of drinking water, the Awash River, and the longer drinking bouts of P. hamadryas. Our findings suggest that differences in delta(18)O values among populations of Papio (modern or ancient) reflect different sources of drinking water (which might have ecological significance) and, further, that Papio has practical value as a paleoenvironmental recorder.

The neurotrophin brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase TrkB serve important regulatory roles for multiple aspects of the biology of neurons including cell death, survival, growth, differentiation, and plasticity. Regulation of the local availability of BDNF/TrkB at distinct subcellular domains such as soma, dendrites, axons, growth cones, nerve terminals, and spines appears to contribute to their specific functions. In view of the variance in size and shape of neurons and their compartments, previous quantitative studies of the BDNF/TrkB protein and mRNA lacked a robust normalization procedure. To overcome this problem, we have established methods that use immunofluorescence detection of alpha-tubulin as a normalization factor for the quantitative analysis of protein and mRNA in primary rat cortical and striatal neurons in culture. The efficacy of this approach is demonstrated by studying the dynamic distribution of proteins and mRNA at different growth stages or conditions. Treatment of cultured neurons with KCl resulted in increased levels of TrkB protein, reduced levels of BDNF mRNA (composite of multiple transcripts) and a slight reduction in BDNF protein levels in the dendrites from the cortex. The KCl treatment also lowered the percentage of BDNF and TrkB proteins in the soma indicative of protein transport. Finally, analysis of the rat cortical and striatal neurons demonstrated comparable or even higher levels of BDNF/TrkB protein and BDNF mRNA in the neurons from the striatum. Thus, in contrast to previous observations made in vivo, striatal neurons are capable of synthesizing BDNF mRNA when cultured in growth media in vitro. The analytical approach presented here provides a detailed understanding of BDNF/TrkB levels in response to a variety of neuronal activities. Our methods could be used broadly, including applications in cell and tissue cytometry, to yield accurate quantitative data of gene expression in cellular and subcellular contexts. (c) 2012 International Society for Advancement of Cytometry.

Most commonly, arrhythmogenic cardiomyopathy (also known as arrhythmogenic right ventricular cardiomyopathy, or ARVC) is caused by mutations in desmosomal proteins. The question arises as to the mechanisms by which mutations in mechanical junctions, affect the rhythm of the heart. We have proposed that a component of the arrhythmogenic substrate may include changes in the function of both, gap junctions and sodium channels. Here, we review the relevant literature on this subject.

There is abundant evidence showing that connexins form gap junctions. Yet this does not exclude the possibility that connexins can exert other functions, separate from that of gap junction (or even a permeable hemichannel) formation. Here, we focus on these noncanonical functions of connexin43 (Cx43), particularly in the heart. We describe two specific examples: the importance of Cx43 on intercellular adhesion, and the role of Cx43 in the function of the sodium channel. We propose that these two functions of Cx43 have important repercussions on the propagation of electrical activity in the heart, irrespective of the presence of permeable gap junction channels. Overall, the gap junction-independent functions of Cx43 in cardiac electrophysiology emerge as an exciting area of future research.

OBJECTIVE: The study aimed determining whether assessment of cartilage oligomeric matrix protein (COMP) degradation products could serve as a serological disease course and therapeutic response predictor in arthritis. METHODS: We generated a panel of monoclonal antibodies against COMP fragments and developed a novel capture enzyme-linked immunosorbent assay (ELISA) for detecting COMP fragments in patients with osteoarthritis (OA) and rheumatoid arthritis (RA). This test was also used to monitor COMP fragments in surgically-induced OA, collagen-induced arthritis (CIA), and tumor necrosis factor (TNF) transgenic animal models. RESULTS: Compared with a commercial COMP ELISA kit that detected no significant difference in COMP levels between OA and control groups, a significant increase of the COMP fragments were noted in the serum of OA patients assayed by this newly established ELISA. In addition, serum COMP fragment levels were well correlated with severity in OA patients and the progression of surgically-induced OA in murine models. Furthermore, the serum levels of COMP fragments in RA patients, mice with CIA, and TNF transgenic mice were significantly higher when compared with their controls. Interestingly, treatment with TNFalpha inhibitors and methotrexate led to a significant decrease of serum COMP fragments in RA patients. Additionally, administration of Atsttrin [Tang, et al., Science 2011;332(6028):478] also resulted in a significant reduction in COMP fragments in arthritis mice models. CONCLUSION: A novel sandwich ELISA is capable of reproducibly measuring serum COMP fragments in both arthritic patients and rodent arthritis models. This test also provides a valuable means to utilize serum COMP fragments for monitoring the effects of interventions in arthritis.

BACKGROUND: Mesenchymal stem cells (MSCs) have shown significant therapeutic potential in preclinical animal models of wound healing. However, the translation of MSC-based therapeutics to clinical practice has been delayed by questions including the mechanisms of MSC homing, engraftment, and ultimate function. THE PROBLEM: Experimental models of MSC-based wound therapies often involve intravenous injection of cells followed by sacrifice of animals at various time points and detection of MSCs in wounds by histological methods. However, this methodology is limited by its sampling of only specific tissue at a single time point and provides no information about how exogenously transplanted MSCs home to the wound environment. BASIC/CLINICAL SCIENCE ADVANCES: Most systemically injected MSCs initially become entrapped within the lungs before migrating out to the liver and spleen in the normal state. When an injury is present, after the initial lung entrapment, MSCs migrate in response to inflammatory mediators and home to sites of wounding. CLINICAL CARE RELEVANCE: As MSC-based wound therapies continue to advance toward clinical trials, the availability of noninvasive methods to track cells after injection into patients affords the opportunity to monitor stem cell behavior post-transplantation. CONCLUSION: MSCs have demonstrated great promise as an emerging therapeutic for wound management. However, further preclinical studies will be needed to elucidate the reparative mechanisms of these cells and to determine how to optimize their regenerative potential.

Prolactinomas are the most prevalent type of secreting pituitary tumors in humans and generally respond well to a medical therapy with dopamine agonists. However, for patients exhibiting resistance to dopaminergic drugs, alternative treatments are desired. Antiangiogenic strategies might represent a potential therapy for these tumors. Thrombospondin 1 (TSP-1) is a large multifunctional glycoprotein involved in multiple biological processes including angiogenesis, apoptosis, and activation of TGF-beta1. Because tumors that overexpress TSP-1 grow more slowly, have fewer metastases, and have decreased angiogenesis, TSP-1 provides a novel target for cancer treatment. ABT-510 and ABT-898 are TSP-1 synthetic analogs that mimic its antiangiogenic action. In the present study, we explored the potential effect of ABT-510 and ABT-898 on experimental prolactinomas induced by chronic diethylstilbestrol (DES) treatment in female rats. We demonstrated that a 2-wk treatment with ABT-510 and ABT-898 counteracted the increase in pituitary size and serum prolactin levels as well as the pituitary proliferation rate induced by DES. These inhibitory effects on tumor growth could be mediated by the antiangiogenic properties of the drugs. We also demonstrated that ABT-510 and ABT-898, in addition to their described antiangiogenic effects, increased active TGF-beta1 level in the tumors. We postulate that the recovery of the local cytokine activation participates in the inhibition of lactotrope function. These results place these synthetic TSP-1 analogs as potential alternative or complementary treatments in dopamine agonist-resistant prolactinomas.

PURPOSE OF REVIEW: Raising HDL cholesterol (HDL-C) has become an attractive therapeutic target to lower cardiovascular risk in addition to statins. Inhibition of the cholesteryl ester transfer protein (CETP), which mediates the transfer of cholesteryl esters from HDL to apolipoprotein B-containing particles, leads to a substantial increase in HDL-C levels. Various CETP inhibitors are currently being evaluated in phase II and phase III clinical trials. However, the beneficial effect of CETP inhibition on cardiovascular outcome remains to be established. RECENT FINDINGS: Torcetrapib, the first CETP inhibitor tested in a phase III clinical trial (ILLUMINATE), failed in 2006 because of an increase in all-cause mortality and cardiovascular events that subsequently were attributed to nonclass-related off-target effects (particularly increased blood pressure and low serum potassium) related to the stimulation of aldosterone production. Anacetrapib, another potent CETP inhibitor, raises HDL-C levels by approximately 138% and decreases LDL cholesterol (LDL-C) levels by approximately 40%, without the adverse off-targets effects of torcetrapib (DEFINE study). The CETP modulator dalcetrapib raises HDL-C levels by approximately 30% (with only minimal effect on LDL-C levels) and proved safety in the dal-VESSEL and dal-PLAQUE trials involving a total of nearly 600 patients. Evacetrapib, a relatively new CETP inhibitor, exhibited favorable changes in the lipid profile in a phase II study. SUMMARY: The two ongoing outcome trials, dal-OUTCOMES (dalcetrapib) and REVEAL (anacetrapib), will provide more conclusive answers for the concept of reducing cardiovascular risk by raising HDL-C with CETP inhibition.

Genome-wide association studies (GWAS) have identified a genetic variant at a locus on chromosome 1p13 that is associated with reduced risk of myocardial infarction, reduced plasma levels of LDL cholesterol (LDL-C), and markedly increased expression of the gene sortilin-1 (SORT1) in liver. Sortilin is a lysosomal sorting protein that binds ligands both in the Golgi apparatus and at the plasma membrane and traffics them to the lysosome. We previously reported that increased hepatic sortilin expression in mice reduced plasma LDL-C levels. Here we show that increased hepatic sortilin not only reduced hepatic apolipoprotein B (APOB) secretion, but also increased LDL catabolism, and that both effects were dependent on intact lysosomal targeting. Loss-of-function studies demonstrated that sortilin serves as a bona fide receptor for LDL in vivo in mice. Our data are consistent with a model in which increased hepatic sortilin binds intracellular APOB-containing particles in the Golgi apparatus as well as extracellular LDL at the plasma membrane and traffics them to the lysosome for degradation. We thus provide functional evidence that genetically increased hepatic sortilin expression both reduces hepatic APOB secretion and increases LDL catabolism, providing dual mechanisms for the very strong association between increased hepatic sortilin expression and reduced plasma LDL-C levels in humans.