Studies on steroid fever: I. Production of leukocyte pyrogen in vitro by etiocholanolone

Endocrine effects of heat exposure and relevance to climate change

Climate change is increasing both seasonal temperatures and the frequency and severity of heat extremes. As the endocrine system facilitates physiological adaptations to temperature changes, diseases with an endocrinological basis have the potential to affect thermoregulation and increase the risk of heat injury. The effect of climate change and associated high temperature exposure on endocrine axis development and function, and on the prevalence and severity of diseases associated with hormone deficiency or excess, is unclear. This Perspective summarizes current knowledge relating to the hormonal effects of heat exposure in species ranging from rodents to humans. We also describe the potential effect of high temperature exposures on patients with endocrine diseases. Finally, we highlight the need for more basic science, clinical and epidemiological research into the effects of heat on endocrine function and health; this research could enable the development of interventions for people most at risk, in the context of rising environmental temperatures.

The role of 5-reduction in physiology and metabolic disease: evidence from cellular, pre-clinical and human studies

The 5-reductases (5α-reductase types 1, 2 and 3 [5αR1-3], 5β-reductase [5βR]) are steroid hormone metabolising enzymes that hold fundamental roles in human physiology and pathology. They possess broad substrate specificity converting many steroid hormones to their 5α- and 5β-reduced metabolites, as well as catalysing crucial steps in bile acid synthesis. 5αRs are fundamentally important in urogenital development by converting testosterone to the more potent androgen 5α-dihydrotestosterone (5αDHT); inactivating mutations in 5αR2 lead to disorders of sexual development. Due to the ability of the 5αRs to generate 5αDHT, they are an established drug target, and 5αR inhibitors are widely used for the treatment of androgen-dependent benign or malignant prostatic diseases. There is an emerging body of evidence to suggest that the 5-reductases can impact upon aspects of health and disease (other than urogenital development); alterations in their expression and activity have been associated with metabolic disease, polycystic ovarian syndrome, inflammation and bone metabolism. This review will outline the evidence base for the extra-urogenital role of 5-reductases from in vitro cell systems, pre-clinical models and human studies, and highlight the potential adverse effects of 5αR inhibition in human health and disease.

5β-Reduced steroids and human Δ(4)-3-ketosteroid 5β-reductase (AKR1D1)

5β-Reduced steroids are non-planar steroids that have a 90° bend in their structure to create an A/B cis-ring junction. This novel property is required for bile-acids to act as emulsifiers, but in addition 5β-reduced steroids have remarkable physiology and may act as potent tocolytic agents, endogenous cardiac glycosides, neurosteroids, and can act as ligands for orphan and membrane bound receptors. In humans there is only a single 5β-reductase gene AKR1D1, which encodes Δ(4)-3-ketosteroid-5β-reductase (AKR1D1). This enzyme is a member of the aldo-keto reductase superfamily, but possesses an altered catalytic tetrad, in which Glu120 replaces the conserved His residue. This predominant liver enzyme generates all 5β-dihydrosteroids in the C19-C27 steroid series. Mutations exist in the AKR1D1 gene, which result in loss of protein stability and are causative in bile-acid deficiency.

Interleukin 1: the first interleukin

The name 'interleukin' and the designation of interleukin 1 (IL-1) derived from the Second International Lymphokine Workshop held in Switzerland in 1979. Since then interest in the original interleukin (IL-1) has increased exponentially as measured by the numbers of publications and meetings. The main reasons for this can be seen in the accompanying centrefold. The perception of IL-1 as a biological mediator in every organ system has attracted scientists from widely different backgrounds into this area and a steady succession of important and often surprising insights into IL-1 biology has ensured that interest has been sustained at a high level. This overview of the biology of IL-1 on the tenth anniversary of its turbulent life has been compiled by Franco di Giovine and Gordon Duff. It is of necessity selective and biased towards human IL-1 and begins with some general points (mainly cautionary) as a backdrop to the centrefold.

Immunomodulation following burn injury

Severe burn injury is accompanied by suppression of almost all the components of immunity; such suppression undoubedly contributes to infectious complications in the burned patient. There has now been substantial experimental progress made in devising approaches to prevent or minimize these immune defects; however, clinical application is still limited.

Molecular basis of fever in humans

This review presents several areas of research on the pathogenesis of fever in humans and updates new information concerning the role of fever in host defense mechanisms. Fever is mediated by a polypeptide of phagocytic cell origin called leukocytic pyrogen. Several agents and disease processes are associated with the synthesis and release of leukocytic pyrogen. Although the original studies on leukocytic pyrogen suggested that the neutrophil was the primary source, recent experiments indicate the mononuclear phagocyte to be the major producer of leukocytic pyrogen. The mechanism by which human monocytes are stimulated to produce leukocytic pyrogen is discussed, including the effects of corticosteroids, estrogens and antipyretics on the synthesis of leukocytic pyrogen in vitro. The ability of leukocytic pyrogen to alter the hypothalamic thermoregulatory center by increasing arachidonic acid metabolite levels is the most likely mechanism by which leukocytic pyrogen initiates fever. Antipyretics prevent the synthesis of certain cyclooxygenase metabolites, which accounts for their ability to reduce fever. Studies on the chemical and physical properties of human leukocytic pyrogen are reviewed and form the basis for current experiments on the similarities between leukocytic pyrogen and lymphocyte activating factor. These studies suggest that leukocytic pyrogen, in addition to producing fever, also stimulates non-hypothalamic cells involved in aspects of the acute-phase response. In this regard, leukocytic pyrogen may be an important mechanism for host defenses. Hyperthermia may also be beneficial to the host but is distinct from fever; the role of leukocytic pyrogen as well as hyperthermia as a defense mechanism is discussed.

Synthesis and pyrogenic effect of 3 alpha, 7 alpha-dihydroxy-5 beta-androstan-17-one and 3 alpha-hydroxy-5 beta-androstane-7, 17-dione

The first chemical synthesis of 3 alpha, 7 alpha-dihydroxy-5 beta-androstan-17-one and 3 alpha-hydroxy-5 beta-androstane-7, 17-dione is reported. In this method, the 17 beta-side chain of commercial chenodesoxycholic acid was degraded in 6 steps after selective protection of the hydroxyl groups: 3 alpha-OH by a tert-butyldimethylsilyl group and 7 alpha-OH by an acetoxy group. The capacity of 3 alpha, 7 alpha-dihydroxy-5 beta-androstan-17-one and 3 alpha-hydroxy-5 beta-androstane-7, 17-dione to release a pyrogen by human leukocytes was investigated by two independent methods: supernatants from leukocytes incubated with a steroid are injected to rabbits whose fever is measured, or tested by the Limulus Test (a pyrogen detection technique). The 7-keto substituted etiocholanolone still possessed pyrogenic activity, while the 7 alpha-hydroxyl substituted one did not.

Colchicine stimulation of pyrogen production by human blood leukocytes

The effect of colchicine, an anti-inflammatory agent, on endogenous pyrogen (EP) production by human blood leukocytes in vitro was examined. Colchicine not only failed to suppress EP production by human leukocytes stimulated by phagocytosis, but, in the absence of other stimuli, micromolar concentrations of the drug induced pyrogen production and release by both polymorphonuclear (PMN) and mononuclear leukocytes. The response was dose related, occurring at concentrations above 0.1 muM. Colcemid and vinblastine, other agents which bind to microtubular protein, also induced pyrogen release from human leukocytes, whereas lumicolchicine, a light-alerted derivative of colchicine without affinity for microtubules, was ineffective. Colchicine did not induce EP production by rabbit leukocytes, even at 100 muM concentration. Studies of the mechanism of PMN leukocyte activation by Colcemid indicated that although the time required for contact between drug and leukocyte was brief, pyrogen production and release did not begin for 6 or more hours. If added during this time, puromycin prevented subsequent production and release of pyrogen. These results indicated that agents which interfere with the assembly of microtubules induce EP production and secretion by human leukocytes in vitro.

Studies on the mechanism of endogenous pyrogen production. II. Role of cell products in the regulation of pyrogen release from blood leukocytes

Some characteristics of the process by which endogenous pyrogen (EP), the mediator of fever, is released from cells were examined by using human blood leukocytes incubated in vitro. Studies were designed to examine a possible role for leukocyte products, including EP, in the induction, augmentation, or suppression of pyrogen release by blood leukocytes. Products of stimulated leukocytes, including a partially purified preparation of EP, did not induce significant activation of nonstimulated cells. Also, no evidence was obtained that stimulated cell products either augment or inhibit pyrogen production by other stimulated cells. A feedback control of EP production was thus not observed. A crude preparation of EP, containing other products of activated cells, maintained its pyrogenicity when incubated at pH 7.4 but not at pH 5.0. These studies thus provide no support for hypothesized control mechanisms regulating production of EP by blood leukocytes. By contrast, local inactivation of EP at inflammatory sites may modify the amount of EP entering the blood, and hence fever.

Pyrogen release in vitro by lymphoid tissues from patients with Hodgkin's disease

The mechanism of fever in patients with Hodgkin's disease was investigated by examining endogenous pyrogen production by blood, spleen, and lymph node cells incubated in vitro. Blood leucocytes from febrile or afebrile patients with Hodgkin's disease did not produce pyrogen spontaneously. Spleen cells, however, frequently released pyrogen during initial incubations, unlike spleen cells from patients with non-malignant diseases. Pyrogen production occurred from spleens without observed pathologic infiltrates of Hodgkin's disease. Lymph nodes involved with Hodgkin's disease produced pyrogen more frequently than did nodes involved with other diseases. Pyrogen production by tissue cells was prolonged, required protein synthesis, and in some cases was due to mononuclear cells; it did not correlate with fever in the patient. These studies demonstrate spontaneous production of endogenous pyrogen in vitro by lymphoid tissue cells from patients with Hodgkin's disease.

Studies on the mechanism of fever accompanying delayed hypersensitivity. The role of the sensitized lymphocyte

Experiments have been carried out to investigate the possible role of the sensitized lymphocyte in mediating the fevers of delayed hypersensitivity. Rabbits were made delayed hypersensitive to one of several heterologous proteins (bovine gamma globulin, bovine serum albumin, or human serum albumin) by footpad injection of antigen or antigen conjugated with dinitrophenol and incorporated in complete Freund's adjuvant. At intervals after sensitization, various tissues were removed, and single cell suspensions were incubated overnight with either carrier protein or conjugate in vitro. Release of an endogenous pyrogen (EP) was assayed by intravenous injection of the supernatant fluid into unsensitized rabbits. Of the tissues tested only those containing both lymphocytes and pyrogen-producing cells, blood, spleen, and draining lymph nodes, released detectable amounts of EP when incubated with antigen in vitro. Incubation of normal blood cells with specifically sensitized lymphocytes and antigen also resulted in significant release of pyrogen. Similarly, blood leukocytes released EP in vitro after mixture with supernates derived from incubation of sensitized lymphocytes and antigen. Cells and supernatant fluids from draining lymph nodes were usually effective in activating normal blood leukocytes earlier after sensitization than were those from mesenteric lymph nodes, suggesting that such cells, or antigen, had migrated from the original site of sensitization. The activator was soluble, nonpyrogenic in the dosages tested, and required incubation of viable cells with specific antigen for its production. These properties suggest that it may belong to the class of "lymphokines," biologically active agents released from lymphocytes that have been activated by immunologic or certain nonimmunologic stimuli.

Studies on steroid fever. II. Pyrogenic and anti-pyrogenic activity in vitro of some endogenous steroids of man

The pyrogenic properties of some C-19 and C-21 steroids were examined by in vitro incubation of human blood leukocytes with serum-buffer solutions of the steroids and injection of the 18-hr supernatants into rabbits. In previous studies this method demonstrated release of leukocyte endogenous pyrogen by etiocholanolone. With two exceptions, steroids known to cause fever in man, such as 11beta-OH etiocholanolone and 3alpha-hydroxy-5beta-pregnane-20-one were also pyrogenic in vitro. All steroids tested which are nonpyrogenic in man, such as androsterone, 3beta-OH etiocholanolone, and 3alpha, 17alpha-dihydroxy-5beta-pregnan-20-one were also nonpyrogenic in vitro. Solubility in aqueous solution did not correlate with pyrogenic capacity. Inhibition of pyrogen release from human leukocytes in vitro by hydrocortisone and estradiol was demonstrated. Hydrocortisone-treated leukocytes released less pyrogen than did normal leukocytes when stimulated either by etiocholanolone or by phagocytosis of heat-killed staphylococci. On the other hand, estradiol-treated blood leukocytes and mononuclear cells showed significant suppression of pyrogen release when phagocytosis, but not etiocholanolone, was used as the stimulus. When blood cells were incubated with progesterone, greater than normal amounts of pyrogen were released following phagocytosis, and the inhibiting effect of estradiol could be partially reversed. Neither estradiol nor hydrocortisone appeared to act on rabbit leukocytes. These studies indicate that a variety of naturally-occurring steroids may alter pyrogen release from leukocytes. Alterations in steroid balance in man may influence normal temperature regulation and contribute to clinical fevers.

Studies on the origin of human leukocytic pyrogen

Release of the protein molecule, leukocytic pyrogen, is one of the many reactions exhibited by leukocytes after phagocytosis. After the ingestion of heat-killed S. albus, a 3-4 hr latent period exists, during which human peripheral leukocytes release no pyrogen, yet cellular metabolism is altered in such a way that pyrogen output may subsequently occur in the absence of further phagocytosis. Transcription of messenger RNA and translation of new protein are initial events in the. activation process, since addition of the inhibitors, actinomycin D, and cycloheximide or puromycin, during this period markedly depressed or abolished subsequent pyrogen release. These effects were noted to be dependent upon the time of addition of the inhibitors. None of the inhibitor drugs interfered with cell viability as measured by phagocytosis and hexose monophosphate shunt activity, nor did they alter the pyrogenicity of preformed leukocytic pyrogen. Vincristine did not inhibit pyrogen formation, consistent with its reported failure to alter RNA synthesis in mature human granulocytes. The glycolytic inhibitor, sodium fluoride, blocked pyrogen release both when added prior to particle ingestion or 1 hr after the initiation of phagocytosis. Whereas inhibition of phagocytosis would explain the sodium fluoride effect prior to 1 hr, this was not observed in leukocyte preparations incubated for 1 hr with S. albus before adding sodium fluoride. When sodium fluoride was added to preparations 2 hr after the start of incubation, the LP production was unimpaired. Potassium cyanide had no effect on cell activation or pyrogen release. These findings suggest that the primary energy supply for the activation process is derived from high energy phosphate bonds provided by anaerobic glycolysis. Since the major amount of cell activation appears to occur in the 1st hr after phagocytosis, this energy might be involved in the induction of a genome leading to the transcription of m-RNA and its translation into new protein or is required for polysome integrity during protein synthesis. It is suggested that this new protein may be leukocytic pyrogen itself, or an enzyme responsible for cleaving it from an inactive precursor.

Species specificity of leukocytic pyrogens

Polymorphonuclear neutrophilic leukocytes of the dog, cat, and goat release leukocytic pyrogen under the same conditions as the heterophile polymorphonuclear leukocytes of the rabbit. The characteristics of the febrile response to an intravenous injection of homologous leukocytic pyrogen in all four species are very similar: a brisk monophasic fever reaching a peak between 30 and 50 min with smooth defervescence to the baseline by 3 hr. Shivering, which is not obvious in the rabbit, is noted in the dog, cat, and goat during the first 30 min. Quantitative differences in response reveal the cat to be the most sensitive of of these species to homologous leukocytic pyrogen, followed by the rabbit, dog, and goat. The response to heterologous pyrogen is in most cases markedly diminished compared to that after equal doses of homologous protein, suggesting the operation of species specificity, although canine and feline pyrogen behaved very similarly in all tests. Species specificity of leukocytic pyrogen is probably related to amino acid substitutions in different species of a common mammalian protein effector molecule.

Recurrent fever of unknown etiology: failure to demonstrate association between fever and plasma unconjugated etiocholanolone

A sensitive method for determination of plasma unconjugated etiocholanolone by double-isotope-derivative dilution has been described. The mean values for normal subjects was 0.038+/-0.003 (SEM) mug/100 ml.40 patients, 20 with familial Mediterranean fever and 20 with other diseases characterized by recurrent fever were studied. The over-all mean concentration of plasma unconjugated etiocholanolone for the patients (febrile or afebrile) was 0.101 +/-0.012 mug/100 ml, significantly above that of normals. Mean plasma values for the patients while they were febrile did not differ from the mean values when they were afebrile. It is suggested that the concentration of plasma unconjugated etiocholanolone is not related to fever in these patients.