Issue published November 1, 2003

T he 146 member nations of the World Trade Organization recently came to an agreement that will allow poor nations to avoid patent restrictions and import generic versions of urgently needed medicines, but this accord has been met with criticism from international aid organizations. What effects will this agreement have on reducing the burden of disease in the developing world, and also on the pharmaceutical industry?

I n a time of emerging genetic tests and technologies, genetic counselors are faced with the challenge of translating complex genomic data into information that will aid their client’s ability to learn about, understand, make, and cope with decisions relating to genetic diagnoses. The first of two companion articles in this issue examines the role of the genetic counselor, particularly in counseling individuals at risk for or diagnosed with breast cancer, in an era of high-tech health care and gene patents.

A s the definition of genetic counseling continues to evolve , so does the application of genetic counseling services in all areas of medicine and throughout the human life cycle. While governmental policy, economics, ethics, and religion continue to influence society’s views regarding the necessity of testing germ cells for mutations to prevent the birth of an affected child or predicting whether healthy adults will develop future life-threatening illness, patient autonomy in the choice of whether to know, or not know, one’s genetic make-up remains a core principle of genetic counseling.

T he existence of species-specific and interspecies bacterial cell-cell communication and group organization was only recently accepted. Researchers are now realizing that the ability of these microbial teams to communicate and form structures, known as biofilms, at key times during the establishment of infection significantly increases their ability to evade both host defenses and antibiotics. This Perspective series discusses the known signaling mechanisms, the roles they play in both chronic Gram-positive and Gram-negative infections, and promising therapeutic avenues of investigation.

U ntil recently, bacteria were considered to live rather asocial, reclusive lives. New research shows that, in fact, bacteria have elaborate chemical signaling systems that enable them to communicate within and between species. One signal, termed AI-2, appears to be universal and facilitates interspecies communication. Many processes, including virulence factor production, biofilm formation, and motility, are controlled by AI-2. Strategies that interfere with communication in bacteria are being explored in the biotechnology industry with the aim of developing novel antimicrobials. AI-2 is a particularly attractive candidate for such studies because of its widespread use in the microbial kingdom.

T raditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. A major concern with this approach is the frequently observed development of resistance to antimicrobial compounds. The discovery of bacterial-communication systems (quorum-sensing systems), which orchestrate important temporal events during the infection process, has afforded a novel opportunity to ameliorate bacterial infection by means other than growth inhibition. Compounds able to override bacterial signaling are present in nature. Herein we discuss the known signaling mechanisms and potential antipathogenic drugs that specifically target quorum-sensing systems in a manner unlikely to pose a selective pressure for the development of resistant mutants.

M ice haploinsufficient for elastin develop structural changes in vessel walls similar to those seen in patients with mutations in the elastin gene. A new study demonstrates that due to mechanical changes in the vessel wall, these animals exhibit increased mean arterial pressures. The results evoke the possibility that alterations in elastin may contribute to the development of essential hypertension in patients.

N aturally arising CD4⁺ regulatory T cells, which engage in the maintenance of immunologic self-tolerance, specifically express FOXP3, which encodes a transcription-repressor protein. Genetic defects in FOXP3 cause IPEX, an X-linked autoimmune/inflammatory syndrome. With FOXP3 as a specific marker for regulatory CD4⁺ T cells in humans, it is now possible to determine their origin and developmental pathway .

I ntestinal colonic crypts are derived from a stem cell population located at the base of each crypt. A new analysis of mitochondrial function and of the rates of mitochondrial DNA (mtDNA) mutation in individual crypts shows that mtDNA mutations arise in stem cells — and at a surprisingly high frequency. Because crypts turn over extremely rapidly (about once per week), somatic mtDNA mutations can “take over the system” and even become homoplasmic, in a manner similar to what has been shown to occur in tumors.

A ntigen-specific lymphocytes are involved in synovial proliferation within inflamed joints. Activated lymphocytes and synoviocytes from patients with rheumatoid arthritis express receptors that can bind TNF-related apoptosis-inducing ligand (TRAIL). A new study demonstrates that DCs pulsed with collagen and transduced with an adenovirus-based vector able to express TRAIL limit the incidence of arthritis in a model of collagen-induced arthritis and joint inflammation. These results suggest that gene-modified cell therapy represents a therapeutic option for systemic rheumatic diseases.

O steopontin (OPN) is expressed in atherosclerotic lesions, particularly in diabetic patients. To determine the role of OPN in atherogenesis, ApoE^–/–OPN^+/+, ApoE^–/–OPN^+/–, and ApoE^–/–OPN^–/– mice were infused with Ang II, inducing vascular OPN expression and accelerating atherosclerosis. Compared with ApoE^–/–OPN^+/+ mice, ApoE^–/–OPN^+/– and ApoE^–/–OPN^–/– mice developed less Ang II–accelerated atherosclerosis. ApoE^–/– mice transplanted with bone marrow derived from ApoE^–/–OPN^–/– mice had less Ang II–induced atherosclerosis compared with animals receiving ApoE^–/–OPN^+/+ cells. Aortae from Ang II–infused ApoE^–/–OPN^–/– mice expressed less CD68, C-C-chemokine receptor 2, and VCAM-1. In response to intraperitoneal thioglycollate, recruitment of leukocytes in OPN^–/– mice was impaired, and OPN^–/– leukocytes exhibited decreased basal and MCP-1–directed migration. Furthermore, macrophage viability in atherosclerotic lesions from Ang II–infused ApoE^–/–OPN^–/– mice was decreased. Finally, Ang II–induced abdominal aortic aneurysm formation in ApoE^–/–OPN^–/– mice was reduced and associated with decreased MMP-2 and MMP-9 activity. These data suggest an important role for leukocyte-derived OPN in mediating Ang II–accelerated atherosclerosis and aneurysm formation.

P reviously, we described an APC-adenovirus (APC-Ad) FasL cell gene therapy method which could be used to deplete autoreactive T cells in vivo. FasL was toxic, however, and controlled regulation of FasL was not achieved. Here we describe an improved approach to delivering TNF-related apoptosis-inducing ligand (TRAIL) in vivo in which collagen II–induced (CII-induced) arthritis–susceptible (CIA-susceptible) DBA/1j mice were treated with CII-pulsed DCs that had been transfected with a novel Ad system. The Ad was engineered to exhibit inducible TRAIL under the control of the doxycycline-inducible (DOX-inducible) tetracycline response element (TRE). Four groups of mice were treated with CII-DC-AdTRAIL+DOX, CII-DC-AdTRAIL (no DOX), CII-DC-AdGFP+DOX, or DC-AdTRAIL+DOX (no CII), beginning 2 weeks after priming with CII in CFA. The incidence of arthritis and infiltration of T cells in the joint was significantly decreased in CII-DC-AdTRAIL+DOX–treated mice. The in vitro splenic T cell proliferative response and induction of IFN-γ to bovine CII stimulation were also significantly reduced in mice treated with CII-DC-AdTRAIL+DOX. AdTRAIL+DOX was not toxic to DCs or mice but could induce activated T cells to undergo apoptosis in the spleen. Our results suggest that CII-DC-AdTRAIL+DOX cell gene therapy is a safe and effective method for inhibiting the development of CIA.

I ncreasing evidence suggests that atherosclerosis is an inflammatory disease promoted by hypercholesterolemia. The role of adaptive immunity has been controversial, however. We hypothesized that proatherogenic T cells are controlled by immunoregulatory cytokines. Among them, TGF-β has been implied in atherosclerosis, but its mechanism of action remains unclear. We crossed atherosclerosis-prone ApoE-knockout mice with transgenic mice carrying a dominant negative TGF-β receptor II in T cells. The ApoE-knockout mice with disrupted TGF-β signaling in T cells exhibited a sixfold increase in aortic lesion surface area, a threefold increase in aortic root lesion size, and a 125-fold increase in aortic IFN-γ mRNA when compared with age-matched ApoE-knockout littermates. When comparing size-matched lesions, those of mice with T cell–specific blockade of TGF-β signaling displayed increased T cells, activated macrophages, and reduced collagen, consistent with a more vulnerable phenotype. Ab’s to oxidized LDL, circulating T cell cytokines, and spleen T cell activity were all increased in ApoE-knockout mice with dominant negative TGF-β receptors in T cells. Taken together, these results show that abrogation of TGF-β signaling in T cells increases atherosclerosis and suggest that TGF-β reduces atherosclerosis by dampening T cell activation. Inhibition of T cell activation may therefore represent a strategy for antiatherosclerotic therapy.

T he mitochondrial genome encodes 13 essential subunits of the respiratory chain and has remarkable genetics based on uniparental inheritance. Within human populations, the mitochondrial genome has a high rate of sequence divergence with multiple polymorphic variants and thus has played a major role in examining the evolutionary history of our species. In recent years it has also become apparent that pathogenic mitochondrial DNA (mtDNA) mutations play an important role in neurological and other diseases. Patients harbor many different mtDNA mutations, some of which are mtDNA mutations, some of which are inherited, but others that seem to be sporadic. It has also been suggested that mtDNA mutations play a role in aging and cancer, but the evidence for a causative role in these conditions is less clear. The accumulated data would suggest, however, that mtDNA mutations occur on a frequent basis. In this article we describe a new phenomenon: the accumulation of mtDNA mutations in human colonic crypt stem cells that result in a significant biochemical defect in their progeny. These studies have important consequences not only for understanding of the finding of mtDNA mutations in aging tissues and tumors, but also for determining the frequency of mtDNA mutations within a cell.

C D4⁺ helper T cells play a critical role in the production of the antinuclear autoantibodies that characterize systemic lupus erythematosus in mice and humans. A key issue is whether this help is derived from a diverse repertoire of autoreactive CD4⁺ T cells or from a select number of T cells of limited specificity. We used the chronic graft-versus-host disease model to define the diversity of the CD4⁺ T cell repertoire required to induce the autoantibody response. By transferring clonally restricted versus clonally diverse populations of MHC class II–reactive CD4⁺ T cells, we show that the loss of B cell tolerance to nuclear antigens has two distinct components with different CD4⁺ cell requirements. Activation of limited repertoires of CD4⁺ T cells was sufficient for the expansion of anergized anti–double-stranded DNA B cells and production of IgM autoantibodies. Unexpectedly, we found that CD4⁺ T cell diversity was necessary for CD4⁺ T cell trafficking into the follicle and for the generation of isotype-switched IgG autoantibodies. Importantly, combining two limited repertoires of T cells provides sufficient CD4⁺ T cell diversity to drive antinuclear Ab production. These data demonstrate that a diverse CD4⁺ T cell repertoire is required to generate a sustained effector B cell response capable of mediating systemic autoimmunity.

A ryl hydrocarbon receptor nuclear translocator (ARNT), a transcription factor of the Per/AHR/ARNT/Sim family, regulates gene expression in response to environmental stimuli including xenobiotics and hypoxia. To examine its role in the epidermis, the Cre-loxP system was used to disrupt the Arnt gene in a keratinocyte-specific manner. Gene-targeted, newborn mice with almost normal appearance died neonatally of severe dehydration caused by water loss. Histology showed small changes in the architecture of cornified layers, with apparently preserved intercorneocyte lamellar structures responsible for the skin barrier function. In contrast, HPLC/ion-trap mass spectrometry revealed significant alterations in the compositions of ceramides, the major components of the lamellae. The murine epidermal ceramides normally contain 4-sphingenine and 4-hydroxysphinganine. In Arnt-null epidermis, 4-sphingenine was largely replaced by sphinganine and the amounts of ceramides with 4-hydroxysphinganine were greatly decreased, suggesting deficiency of dihydroceramide desaturases that catalyze the formation of both 4-sphingenyl and 4-hydroxysphinganyl moieties. A desaturase isoenzyme, DES-1, prefers desaturation, but DES-2 catalyzes both reactions to a similar extent. Transcript levels of Des-2, but not Des-1, were considerably decreased in cultured keratinocytes from Arnt-null epidermis. These results indicate that proper ceramide compositions through 4-desaturation regulated by ARNT are crucial for maintaining the epidermal barrier function.

A ngiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II–induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47^phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen α1(I) mRNA expression, and secretion of TGF-β1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47^phox–/– mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47^phox–/– mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle α-actin and expression of TGF-β1 were reduced in p47^phox–/– mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.

T hioredoxin 1 (Trx1) has redox-sensitive cysteine residues and acts as an antioxidant in cells. However, the extent of Trx1 contribution to overall antioxidant mechanisms is unknown in any organs. We generated transgenic mice with cardiac-specific overexpression of a dominant negative (DN) mutant (C32S/C35S) of Trx1 (Tg-DN-Trx1 mice), in which the activity of endogenous Trx was diminished. Markers of oxidative stress were significantly increased in hearts from Tg-DN-Trx1 mice compared with those from nontransgenic (NTg) mice. Tg-DN-Trx1 mice exhibited cardiac hypertrophy with maintained cardiac function at baseline. Intraperitoneal injection of N-2-mercaptopropionyl glycine, an antioxidant, normalized cardiac hypertrophy in Tg-DN-Trx1 mice. Thoracic aortic banding caused greater increases in myocardial oxidative stress and enhanced hypertrophy in Tg-DN-Trx1 compared with NTg mice. In contrast, transgenic mice with cardiac-specific overexpression of wild-type Trx1 did not show cardiac hypertrophy at baseline but exhibited reduced levels of hypertrophy and oxidative stress in response to pressure overload. These results demonstrate that endogenous Trx1 is an essential component of the cellular antioxidant mechanisms and plays a critical role in regulating oxidative stress in the heart in vivo. Furthermore, inhibition of endogenous Trx1 in the heart primarily stimulates hypertrophy, both under basal conditions and in response to pressure overload through redox-sensitive mechanisms.

S tem cell factor (SCF) is a molecule with known proliferative effects on hematopoietic cells. More recent studies suggest that this molecule may also have effects on cellular differentiation and proliferation in other types of cells. The current investigations demonstrate that there is a large reservoir of SCF in the liver, that hepatic SCF levels change dramatically following partial hepatectomy in mice, and that SCF blockade, either by administration of anti-SCF antibodies or by using genetically altered, SCF-deficient mice, inhibits hepatocyte proliferation after partial hepatectomy; if SCF is replaced in the genetically SCF-deficient mice after partial hepatectomy, hepatocyte proliferation is restored to that seen in WT animals. Furthermore, SCF administration to IL-6 knockout mice also restores hepatocyte proliferation to normal. In vitro studies using primary mouse hepatocytes demonstrate that SCF causes hepatocyte proliferation and is induced by IL-6 and that treatment with anti-SCF antibodies inhibits IL-6–induced hepatocyte proliferation. Further in vivo studies in IL-6 knockout mice demonstrate that SCF administration to these animals increases p-stat3 levels, suggesting that the SCF-induced increase in hepatocyte proliferation in this system is stat3-mediated.

S upravalvular aortic stenosis is an autosomal-dominant disease of elastin (Eln) insufficiency caused by loss-of-function mutations or gene deletion. Recently, we have modeled this disease in mice (Eln^+/–) and found that Eln haploinsufficiency results in unexpected changes in cardiovascular hemodynamics and arterial wall structure. Eln^+/– animals were found to be stably hypertensive from birth, with a mean arterial pressure 25–30 mmHg higher than their wild-type counterparts. The animals have only moderate cardiac hypertrophy and live a normal life span with no overt signs of degenerative vascular disease. Examination of arterial mechanical properties showed that the inner diameters of Eln^+/– arteries were generally smaller than wild-type arteries at any given intravascular pressure. Because the Eln^+/– mouse is hypertensive, however, the effective arterial working diameter is comparable to that of the normotensive wild-type animal. Physiological studies indicate a role for the renin-angiotensin system in maintaining the hypertensive state. The association of hypertension with elastin haploinsufficiency in humans and mice strongly suggests that elastin and other proteins of the elastic fiber should be considered as causal genes for essential hypertension.

L arge amounts of calcium are transferred to offspring by milk. This demand results in negative calcium balance in lactating mothers and is associated with rapid bone loss. The mechanisms of bone loss during lactation are only partly understood. Several studies have suggested that parathyroid hormone–related protein (PTHrP) might be secreted into the circulation by the lactating mammary gland and regulate bone turnover during lactation. Because mammary development fails in the absence of PTHrP, conventional PTHrP knockout mice cannot be used to address this possibility. To examine this hypothesis, we therefore used mice carrying a β-lactoglobulin promoter-driven Cre transgene, one null PTHrP allele, and one floxed PTHrP allele. Expression of Cre specifically in mammary epithelial cells during late pregnancy and lactation resulted in efficient deletion of the PTHrP gene; mammary gland PTHrP mRNA and milk PTHrP protein were almost completely absent. Removal of PTHrP from the lactating mammary glands resulted in reductions in levels of circulating PTHrP and 1,25-dihydroxy vitamin D and urinary cAMP. In addition, bone turnover was reduced and bone loss during lactation was attenuated. We conclude that during lactation mammary epithelial cells are a source of circulating PTHrP that promotes bone loss by increasing rates of bone resorption.

C D4⁺CD25⁺ regulatory T (T_R) cells have been described in both humans and mice. In mice, T_R are thymically derived, and lack of T_R leads to organ-specific autoimmunity. Recently, the forkhead/winged helix transcription factor, FoxP3, has been shown to be important for the function of T_R cells in mice. In this study, human T_R cells were examined and, in results similar to those of studies done in mice, expression of FoxP3 was found exclusively in CD4⁺CD25⁺ T cells and correlated with the suppressive activity of these cells. In contrast to the mouse studies, activation of human CD4⁺CD25^– T cells led to expression of FoxP3. Expression of FoxP3 in activated human CD4⁺CD25⁺ cells also correlated with suppression of proliferation by these cells in freshly isolated CD4⁺CD25^– T cells from the same donor. This suppression was cell-contact dependent and cytokine independent. Thus, in humans, during activation of CD4⁺CD25^– T cells in an immune response, two populations of cells may arise, effector CD4⁺CD25⁺ and regulatory CD4⁺CD25⁺ T cells, with expression of FoxP3 correlated with regulatory activity. These data also raise the possibility that a failure to generate peripheral T_R cells properly may contribute to autoimmune disease and suggest a possible therapeutic role for FoxP3 in the treatment of such diseases.

T he α1β1 integrin, very late antigen-1 (VLA-1), is a collagen receptor expressed in many CD4⁺ T cells localizing to inflamed tissues. Here we show that the expression of VLA-1 is a stable marker of a distinct subset of CD4⁺ memory T cells. Thus, in human peripheral blood lymphocytes (PBLs), approximately 1–4% of the CD4⁺ T cells express VLA-1, and following T cell receptor activation ex vivo, the percentage of VLA-1⁺ cells increases within the CD45RO⁺ population. Importantly, the activated VLA-1⁺ and VLA-1^– cells can be isolated and maintained in culture as phenotypically stable subsets. Functionally, CD4⁺ memory T cells, operationally defined as the cells that divide rapidly following stimulation with a recall antigen, are highly enriched for VLA-1⁺ cells. Moreover, depletion of the small fraction of VLA-1⁺ cells present in CD4⁺ PBLs prior to stimulation significantly abrogated the proliferative response to recall antigens. Notably, the VLA-1⁺ cells in fresh CD4⁺ PBLs are composed of resting CD45RO⁺/RA^–, CCR7^–, CD62L⁺, CD25^–, and VLA-4^hi cells. Interestingly, this VLA-1⁺ subset is enriched for Th1-type cells, and Th1-polarizing conditions during T cell activation favor the emergence of VLA-1⁺ cells. Thus, VLA-1 expression is a stable marker of a unique subset of human memory CD4⁺ T cells that predominantly differentiates into Th1 cells.