Thermoregulatory phenotype of the Trpv1 knockout mouse: thermoeffector dysbalance with hyperkinesis.

This study aimed at determining the thermoregulatory phenotype of mice lacking transient receptor potential vanilloid-1 (TRPV1) channels. We used Trpv1 knockout (KO) mice and their genetically unaltered littermates to study diurnal variations in deep body temperature (T(b)) and thermoeffector activities under basal conditions, as well as thermoregulatory responses to severe heat and cold. Only subtle alterations were found in the basal T(b) of Trpv1 KO mice or in their T(b) responses to thermal challenges. The main thermoregulatory abnormality of Trpv1 KO mice was a different pattern of thermoeffectors used to regulate T(b). On the autonomic side, Trpv1 KO mice were hypometabolic (had a lower oxygen consumption) and hypervasoconstricted (had a lower tail skin temperature). In agreement with the enhanced skin vasoconstriction, Trpv1 KO mice had a higher thermoneutral zone. On the behavioral side, Trpv1 KO mice preferred a lower ambient temperature and expressed a higher locomotor activity. Experiments with pharmacological TRPV1 agonists (resiniferatoxin and anandamide) and a TRPV1 antagonist (AMG0347) confirmed that TRPV1 channels located outside the brain tonically inhibit locomotor activity. With age (observed for up to 14 months), the body mass of Trpv1 KO mice exceeded that of controls, sometimes approaching 60 g. In summary, Trpv1 KO mice possess a distinct thermoregulatory phenotype, which is coupled with a predisposition to age-associated overweight and includes hypometabolism, enhanced skin vasoconstriction, decreased thermopreferendum, and hyperkinesis. The latter may be one of the primary deficiencies in Trpv1 KO mice. We propose that TRPV1-mediated signals from the periphery tonically suppress the general locomotor activity.

Transplantation of allogeneic T cells alters iron homeostasis in NOD/SCID mice.

Iron overload is common in patients undergoing allogeneic hematopoietic cell transplantation (HCT), but the mechanisms leading to overload are unknown. Here, we determined iron levels and the expression of iron regulatory proteins in the liver and gut of nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice that underwent transplantation with syngeneic (histocompatible) or allogeneic (histoincompatible) T lymphocytes. Infusion of histoincompatible T cells resulted in a significant rise in serum iron levels and liver iron content. Iron deposition was accompanied by hepatocyte injury and intestinal villous damage. Feeding of low- or high-iron diet was associated with appropriate ferroportin 1 and hepcidin responses in mice given histocompatible T cells, whereas mice given histoincompatible T cells showed inappropriate up-regulation of duodenal ferroportin 1 and a loss of expression of hepatic hepcidin. These findings suggest that alloreactive T cell-dependent signals induced dysregulation of intestinal iron absorption, which contributed to liver iron overload after HCT.

A preclinical model of double- versus single-unit unrelated cord blood transplantation.

Cord blood transplantation (CBT) with units containing total nucleated cell (TNC) dose >2.5 x 10(7)/kg is associated with improved engraftment and decreased transplant-related mortality. For many adults no single cord blood units are available that meet the cell dose requirements. We developed a dog model of CBT to evaluate approaches to overcome the problem of low cell dose cord blood units. This study primarily compared double- versus single-unit CBT. Unrelated dogs were bred and cord blood units were harvested. We identified unrelated recipients that were dog leukocyte antigen (DLA)-88 (class I) and DLA-DRB1 (class II) allele-matched with cryopreserved units. Each unit contained

Transferrin fails to provide protection against Fas-induced hepatic injury in mice with deletion of functional transferrin-receptor type 2.

We reported previously that Fas-induced hepatic failure in normal mice was attenuated or prevented by exogenous transferrin (Tf), particularly apoTf. Here we show in C57BL6J/129 mice with genetic inactivation of transferrin receptor 2 (TfR2(Y245X)), that Fas-induced hepatotoxicity (apoptosis; rise in plasma aspartate aminotransferase (AST) levels) was comparable to that in wild-type mice, but was not modified by pretreatment with Tf. Rises in plasma AST were preceded by a decline in serum iron levels. AST elevations and iron declines were more profound in female than in male mice. Female mice also showed higher baseline levels of Bcl-xL in hepatocytes, which declined significantly upon treatment with agonistic anti-Fas antibody. These data confirm the cytoprotective function of Tf, and show a novel property of TfR2. Both apoptotic Fas responses and cytoprotective effects of Tf were associated with significant shifts in plasma iron levels, which quantitatively differed between male and female mice.

Neuroimmunomodulation and aging: a role for transferrin and the hypothalamus/thymus axis.

Advanced age is associated with an increased incidence of immune and degenerative disorders, mediated by metabolic changes, dysregulation of proinflammatory signals, and apoptosis. Concurrently, there is a progressive decline in self-recognition. Investigations on biologic functions of transferrin (Tf) other than iron transport showed that Tf has a profound cytoprotective (anti-apoptotic) effect on lympho-hematopoietic cells and the thymus, and interferes with stress-induced signals. Tf protects hepatocytes against Fas-induced cell death by reducing BID cleavage, inhibiting caspase-3 and -9 activation and up-regulating survival signals such as Bcl-xL. The involvement in the regulation of alloreactivity and apoptosis suggests that Tf participates in the maintenance of "self-identity" mechanisms, which are tightly linked to the capacity of the immune system to recognize and react against any noxious agent. Some of the disorders associated with aging are thought to be related to thymic involution, reflecting alterations in the interplay of neural, endocrine and immune factors. We established a murine model of thymic involution induced by stereotactically placed electrolytic lesions in the anterior hypothalamic area. The events observed in this model mimic those observed during senescence including thymus involution, i.e. enhanced glucocorticoid reaction to distress, and obesity. The described properties of Tf can be exploited to modify immune responses and provide cytoprotection against pro-apoptotic and cytotoxic signals when neuroimmunomodulatory mechanisms are impaired, as is the case with aging.

Effects of long-term intraperitoneal injection of thyrotropin-releasing hormone (TRH) on aging- and obesity-related changes in body weight, lipid metabolism, and thyroid functions.

Adult adipose mice, high fat diet-fed (HFD) mice, anterior hypothalamus-lesioned obese mice and genetically obese mice, were injected daily with thyrotropin releasing hormone (TRH). The treatment provoked a mobilization of triglycerides in the peripheral blood, a decrease of leptin and a loss of body weight. The weight loss did not depend on TSH-mediated stimulation of thyroid hormone secretion with consequent metabolic hyperthyroidism. The levels of blood cholesterol were not affected or even suppressed. Even at a very high dosage TRH did not affect the obesity of genetically obese mice. The ubiquitous tripeptide TRH may thus constitute a key element in the hormone-controlled regulation of body weight and fat stores in the adult and aging body.

NF-kappaB and FLIP in arsenic trioxide (ATO)-induced apoptosis in myelodysplastic syndromes (MDSs).

Tumor necrosis factor (TNF)-alpha, a potent stimulus of nuclear factor-kappaB (NF-kappaB), is up-regulated in myelodysplastic syndrome (MDS). Here, we show that bone marrow mononuclear cells (BMMCs) and purified CD34+ cells from patients with low-grade/early-stage MDS (refractory anemia/refractory anemia with ring sideroblasts [RA/RARS]) have low levels of NF-kappaB activity in nuclear extracts comparable with normal marrow, while patients with RA with excess blasts (RAEB) show significantly increased levels of activity (P = .008). Exogenous TNF-alpha enhanced NF-kappaB nuclear translocation in MDS BMMCs above baseline levels. Treatment with arsenic trioxide (ATO; 2-200 microM) inhibited NF-kappaB activity in normal marrow, primary MDS, and ML1 cells, even in the presence of exogenous TNF-alpha (20 ng/mL), and down-regulated NF-kappaB-dependent antiapoptotic proteins, B-cell leukemia XL (Bcl-XL), Bcl-2, X-linked inhibitor of apoptosis (XIAP), and Fas-associated death domain (FADD)-like interleukin-1beta-converting enzyme (FLICE) inhibitory protein (FLIP), leading to apoptosis. However, overexpression of FLIP resulted in increased NF-kappaB activity and rendered ML1 cells resistant to ATO-induced apoptosis. These data are consistent with the observed up-regulation of FLIP and resistance to apoptosis with advanced MDS, where ATO as a single agent may show only limited efficacy. However, the data also suggest that combinations of ATO with agents that interfere with other pathways, such as FLIP autoamplification via NF-kappaB, may have considerable therapeutic activity.

Prevention of Fas-mediated hepatic failure by transferrin.

Recent studies in lymphohemopoietic cells show that transferrin (Tf), a pivotal component of iron transport and metabolism, also exerts cytoprotective functions. We show here in a murine model that Tf interferes with Fas-mediated hepatocyte death and liver failure. The mechanism involves the downregulation of apoptosis via BID, cytochrome c, caspase-3 and caspase-9, and upregulation of antiapoptotic signals via Bcl-xL. The results obtained with iron-saturated Tf, Apo-Tf and the iron-chelator salicylaldehyde isonicotinoyl hydrazone indicate that the observed antiapoptotic effect of Tf was not mediated by iron alone. In conclusion, the data suggest that Tf has broader functions than previously recognized and may serve as a cytoprotective agent.