The Hypothalamic-Pituitary-Adrenal Axis: A Brief History

The hypothalamic-pituitary-adrenal (HPA) axis is central to homeostasis, stress responses, energy metabolism, and neuropsychiatric function. The history of this complex system involves discovery of the relevant glands (adrenal, pituitary, hypothalamus), hormones (cortisol, corticotropin, corticotropin-releasing hormone), and the receptors for these hormones. The adrenal and pituitary were identified by classical anatomists, but most of this history has taken place rather recently, and has involved complex chemistry, biochemistry, genetics, and clinical investigation. The integration of the HPA axis with modern neurology and psychiatry has cemented the role of endocrinology in contemporary studies of behavior.

[The century of the receptor, history of ideas that launched psychopharmacology]

Nowadays, the term receptor is obvious in psychopharmacology. However, this was not so obvious a century ago. To try to explain how drugs act, European scientists began to develop theories that turned into deeds with the scientific progress. Thus, the receptor concept and their applications in medicine and psychiatry began to gain substance. In this paper we relate the facts that have led to the current knowledge of receptor, the cornerstone of pharmacology.

The receptor concept: pharmacology's big idea

Chemical signalling is the main mechanism by which biological function is controlled at all levels, from the single cell to the whole organism. Chemical recognition is the function of receptors, which, in addition to recognising endogenous chemical signals, are also the target of many important experimental and therapeutic drugs. Receptors, therefore, lie at the heart of pharmacology. This article describes the way in which the receptor concept originated early in the 20th century, and evolved through a highly innovative stage of quantitative theory based on chemical kinetics, to the point where receptors were first isolated and later cloned, until we now have a virtually complete catalogue of all the receptors present in the genome. Studies on signal transduction are revealing great complexity in the events linking ligand binding to the physiological or therapeutic response. Though some simple quantitative rules of 'receptor theory' are still useful, the current emphasis is on unravelling the pathways that link receptors to responses, and it will be some time before we know enough about them to embark on the next phase of 'receptor theory'.

Synthetic peptides as probes for conformational preferences of domains of membrane receptors

Peptide models have been widely used to investigate conformational aspects of domains of proteins since the early 1950s. A pioneer in this field was Dr. Murray Goodman, who applied a battery of methodologies to study the onset of structure in homooligopeptides. This article reviews some of Dr. Goodman's contributions, and reports recent studies using linear and constrained peptides corresponding to the first extracellular loop and linear peptides corresponding to the sixth transmembrane domain of a G-protein coupled receptor from the yeast Saccharomyces cerevisiae. Peptides containing 30-40 residues were synthesized using solid-phase methods and purified to near homogeneity by reversed phase high performance liquid chromatography. CD and NMR analyses indicated that the first extracellular loop peptides were mostly flexible in water, and assumed some helical structure near the N-terminus in trifluoroethanol and in the presence of micelles. Comparison of oligolysines with native loop residues revealed that three lysines at each terminus of a peptide corresponding to the sixth transmembrane domain of the alpha-factor receptor resulted in better aqueous solubility and greater helicity than the native loop residues.

TLRs: Professor Mechnikov, sit on your hat

Toll-like receptors (TLRs) are sensors of foreign microbial products, which initiate host defense responses in all multicellular organisms examined to date. They are the target for most adjuvants, are essential for the establishment of memory in T and B cells and provoke inflammation. They program dendritic cells in their interaction with Th1 cells and their signalling pathways enable a tailoring of host defense responses to the provoking microbe previously unsuspected in the innate arm of immunity. Their discovery and characterisation fills a void in immunology and is the culmination of an effort that began with one of immunology's founding fathers, Elie Mechnikov. Targeting TLRs therapeutically now has the potential to impact on how we treat infectious and inflammatory diseases.

Liposomes as Protein Carriers in Immunology

Liposomes are excellent carriers for protein antigens since they can contain large amounts of antigen, potentially in association with adjuvants. Liposomes may be made to mimic the pathogens that stimulated the evolution of the immune system. As such, numerous mechanisms exist to promote their uptake by antigen presenting cells and exposure of encapsulated antigens to the lymphocytes of the immune system for the induction of responses. The review is intended to describe the 30 year history of the use of liposomes are carriers of protein antigens, notably from the perspective of what we have learned about the immune system using liposomes.

Innate immune sensing and its roots: the story of endotoxin

How does the host sense pathogens? Our present concepts grew directly from longstanding efforts to understand infectious disease: how microbes harm the host, what molecules are sensed and, ultimately, the nature of the receptors that the host uses. The discovery of the host sensors--the Toll-like receptors--was rooted in chemical, biological and genetic analyses that centred on a bacterial poison, termed endotoxin.