MAP kinase (ERK) translates cell surface signals into alterations in transcription. We have found that ERK also regulates hippocampal neuronal excitability during 5 Hz stimulation and thereby regulates forms of long-term potentiation (LTP) that do not require macromolecular synthesis. Moreover, ERK-mediated changes in excitability are selectively required for some forms of LTP but not others. ERK is required for the early phase of LTP elicited by brief 5 Hz stimulation, as well as for LTP elicited by more prolonged 5 Hz stimulation when paired with beta1-adrenergic receptor activation. By contrast, ERK plays no role in LTP elicited by a single 1 s 100 Hz train. Consistent with these results, we find that ERK is activated by beta-adrenergic receptors in CA1 pyramidal cell somas and dendrites.

alpha2-Adrenergic receptors (alpha2ARs) are essential components of the neural circuitry regulating cardiovascular function. The role of specific alpha2AR subtypes (alpha2a, alpha2b, and alpha2c) was characterized with hemodynamic measurements obtained from strains of genetically engineered mice deficient in either alpha2b or alpha2c receptors. Stimulation of alpha2b receptors in vascular smooth muscle produced hypertension and counteracted the clinically beneficial hypotensive effect of stimulating alpha2a receptors in the central nervous system. There were no hemodynamic effects produced by disruption of the alpha2c subtype. These results provide evidence for the clinical efficacy of more subtype-selective alpha2AR drugs.

␤-Adrenergic receptors (␤-ARs) are members of the superfamily of G-protein-coupled receptors that mediate the effects of catecholamines in the sympathetic nervous system. Three distinct ␤-AR subtypes have been identified (␤1-AR, ␤2-AR, and ␤3-AR). In order to define further the role of the different ␤-AR subtypes, we have used gene targeting to inactivate selectively the ␤2-AR gene in mice. Based on intercrosses of heterozygous knockout (␤2-AR ؉/؊) mice, there is no prenatal lethality associated with this mutation. Adult knockout mice (␤2-AR ؊/؊) appear grossly normal and are fertile. Their resting heart rate and blood pressure are normal, and they have a normal chronotropic response to the ␤-AR agonist isoproterenol. The hypotensive response to isoproterenol, however, is significantly blunted compared with wild type mice. Despite this defect in vasodilation, ␤2-AR ؊/؊ mice can still exercise normally and actually have a greater total exercise capacity than wild type mice. At comparable workloads, ␤2-AR ؊/؊ mice had a lower respiratory exchange ratio than wild type mice suggesting a difference in energy metabolism. ␤2-AR ؊/؊ mice become hypertensive during exercise and exhibit a greater hypertensive response to epinephrine compared with wild type mice. In summary, the primary physiologic consequences of the ␤2-AR gene disruption are observed only during the stress of exercise and are the result of alterations in both vascular tone and energy metabolism.

The activation state of ␤-adrenergic receptors (␤-ARs) in vivo is an important determinant of hemodynamic status, cardiac performance, and metabolic rate. In order to achieve homeostasis in vivo, the cellular signals generated by ␤-AR activation are integrated with signals from a number of other distinct receptors and signaling pathways. We have utilized genetic knockout models to test directly the role of ␤1-and/or ␤2-AR expression on these homeostatic control mechanisms. Despite total absence of ␤1-and ␤2-ARs, the predominant cardiovascular ␤-adrenergic subtypes, basal heart rate, blood pressure, and metabolic rate do not differ from wild type controls. However, stimulation of ␤-AR function by ␤-AR agonists or exercise reveals significant impairments in chronotropic range, vascular reactivity, and metabolic rate. Surprisingly, the blunted chronotropic and metabolic response to exercise seen in ␤1/ ␤2-AR double knockouts fails to impact maximal exercise capacity. Integrating the results from single ␤1-and ␤2-AR knockouts as well as the ␤1-/␤2-AR double knockout suggest that in the mouse, ␤-AR stimulation of cardiac inotropy and chronotropy is mediated almost exclusively by the ␤1-AR, whereas vascular relaxation and metabolic rate are controlled by all three ␤-ARs (␤1-, ␤2-, and ␤3-AR). Compensatory alterations in cardiac muscarinic receptor density and vascular ␤3-AR responsiveness are also observed in ␤1-/␤2-AR double knockouts. In addition to its ability to define ␤-AR subtype-specific functions, this genetic approach is also useful in identifying adaptive alterations that serve to maintain critical physiological setpoints such as heart rate, blood pressure, and metabolic rate when cellular signaling mechanisms are perturbed.

Women develop certain autoimmune diseases more often than men. It has been hypothesized that this may relate to the development of more robust T-helper (Th)1 responses in women. To test whether women exhibit a Th1 bias, we isolated naïve cluster of differentiation (CD)4 + T cells from peripheral blood of healthy women and men and measured the proliferation and cytokine production by these cells in response to submaximal amounts of anti-CD3 and anti-CD28. We observed that CD4 + T cells from women produced higher levels of IFNγ as well as tended to proliferate more than male CD4 + T cells. Intriguingly, male CD4 + T cells instead had a predilection toward IL-17A production. This sex dichotomy in Th cytokine production was found to be even more striking in the Swiss/Jackson Laboratory (SJL) mouse. Studies in mice and humans indicated that the sexual dimorphism in Th1 and Th17 cytokine production was dependent on the androgen status and the T-cell expression of peroxisome proliferator activated receptor (PPAR)α and PPARγ. Androgens increased PPARα and decreased PPARγ expression by human CD4 + T cells. PPARα siRNA-mediated knockdown had the effect of increasing IFNγ by male CD4 + T cells, while transfection of CD4 + T cells with PPARγ siRNAs increased IL-17A production uniquely by female T cells. Together, our observations indicate that human T cells exhibit a sex difference in the production of IFNγ and IL-17A that may be driven by expressions of PPARα and PPARγ. autoimmunity | cytokines | experimental autoimmune encephalomyelitis | gender | nuclear receptor

The T cell antigen receptor (TCR)-CD3 complex is unique in having ten cytoplasmic immunoreceptor tyrosine-based activation motifs (ITAMs). The physiological importance of this high TCR ITAM number is unclear. Here we generated 25 groups of mice expressing various combinations of wild-type and mutant ITAMs in TCR-CD3 complexes. Mice with fewer than seven wild-type CD3 ITAMs developed a lethal, multiorgan autoimmune disease caused by a breakdown in central rather than peripheral tolerance. Although there was a linear correlation between the number of wild-type CD3 ITAMs and T cell proliferation, cytokine production was unaffected by ITAM number. Thus, high ITAM number provides scalable signaling that can modulate proliferation yet ensure effective negative selection and prevention of autoimmunity.

beta-Adrenergic receptors (beta-AR) are essential regulators of cardiovascular homeostasis. In addition to their prominent function in the heart, beta-AR are located on vascular smooth muscle cells, where they mediate vasodilating effects of endogenous catecholamines. In this study, we have investigated in an isometric myograph different types of blood vessels from mice lacking beta(1)- and/or beta(2)-adrenergic receptor subtypes (beta(1)-KO, beta(2)-KO, beta(1)beta(2)-KO). In wild-type mice, isoproterenol induced relaxation of segments from thoracic aorta, carotid, femoral and pulmonary arteries, and portal vein. The relaxant effect of beta-receptor stimulation was absent in femoral and pulmonary arteries from beta(1)-KO mice. In aortic and carotid arteries and in portal veins, the vasodilating effect of isoproterenol was reduced in mice lacking beta(1)- or beta(2)-receptors. However, in these vessels the vasodilating effect was only abolished in double KO mice lacking both beta(1)- and beta(2)-receptors. Vessel relaxation induced by forskolin did not differ between wild-type and KO mice. Similar contributions of beta(1)- and beta(2)-receptors to isoproterenol-induced vasorelaxation were found when vessels from KO mice were compared with wild-type arteries in the presence of subtype-selective beta-receptor antagonists. These studies demonstrate that beta(1)-adrenergic receptors play a dominant role in the murine vascular system to mediate vasodilation. Surprisingly, beta(2)-receptors contribute to adrenergic vasodilation only in a few major blood vessels, suggesting that differential distribution of beta-adrenergic receptor subtypes may play an important role in redirection of tissue perfusion.

Pathological angiogenesis contributes to tobacco-related diseases such as malignancy, atherosclerosis and age-related macular degeneration. Nicotine acts on endothelial nicotinic acetylcholine receptors (nAChRs) to activate endothelial cells and to augment pathological angiogenesis. In the current study, we studied nAChR subunits involved in these actions. We detected mRNA for all mammalian nAChR subunits except α2, α4, γ and δ in four different types of ECs. Using siRNA methodology, we found that the α7 nAChR plays a dominant role in nicotine-induced cell signaling (assessed by intracellular calcium and NO imaging, and studies of protein expression and phosphorylation), as well as nicotine-activated EC functions (proliferation, survival, migration and tube formation). The α9 and α7 nAChRs have opposing effects on nicotine-induced cell proliferation and survival. Our studies reveal a critical role for the α7 nAChR in mediating the effects of nicotine on the endothelium. Other subunits play a modulatory role. These findings may have therapeutic implications for diseases characterized by pathological angiogenesis.