Effect of interferon-gamma treatment on 24-hour variations in plasma ACTH, growth hormone, prolactin, luteinizing hormone and follicle-stimulating hormone of male rats

Complement Has Brains-Do Intracellular Complement and Immunometabolism Cooperate in Tissue Homeostasis and Behavior?

The classical liver-derived and serum-effective complement system is well appreciated as a key mediator of host protection via instruction of innate and adaptive immunity. However, recent studies have discovered an intracellularly active complement system, the complosome, which has emerged as a central regulator of the core metabolic pathways fueling human immune cell activity. Induction of expression of components of the complosome, particularly complement component C3, during transmigration from the circulation into peripheral tissues is a defining characteristic of monocytes and T cells in tissues. Intracellular complement activity is required to induce metabolic reprogramming of immune cells, including increased glycolytic flux and OXPHOS, which drive the production of the pro-inflammatory cytokine IFN-γ. Consequently, reduced complosome activity translates into defects in normal monocyte activation, faulty Th1 and cytotoxic T lymphocyte responses and loss of protective tissue immunity. Intriguingly, neurological research has identified an unexpected connection between the physiological presence of innate and adaptive immune cells and certain cytokines, including IFN-γ, in and around the brain and normal brain function. In this opinion piece, we will first review the current state of research regarding complement driven metabolic reprogramming in the context of immune cell tissue entry and residency. We will then discuss how published work on the role of IFN-γ and T cells in the brain support a hypothesis that an evolutionarily conserved cooperation between the complosome, cell metabolism and IFN-γ regulates organismal behavior, as well as immunity.

Individual and interactive sex-specific effects of acute restraint and systemic IFN-γ treatment on neurochemistry

Compelling evidence supports the involvement of the pro-inflammatory cytokines, IL-6, IFN-α and TNF-α in depression and related stress-associated pathologies. A role has also been suggested for the Th1-type cytokine, IFN-γ, with most mechanistic accounts focusing on the cytokine's capacity to induce indoleamine 2,3-dioxygenase (IDO), leading to diminished tryptophan and the generation of kynurenine metabolites. Beyond these IDO-dependent routes, there is surprisingly little evidence directly linking IFN-γ to alterations of brain regional monoamine activity and HPA axis functioning. Our specific aims in the present study were twofold: 1) assess the behavioural, plasma corticosterone and brain regional monoamine effects of acute systemic IFN-γ, with or without short duration restraint stress (15 min), and 2) determine the sex-specific nature of these effects. As predicted, IFN-γ stimulated monoaminergic activity within a number of stressor-sensitive limbic brain regions, most notably the paraventricular nucleus of the hypothalamus, central amygdala and prefrontal cortex. While several of these effects were sex-specific, there was little in the way of synergism between the cytokine and stressor treatments. Nonetheless, IFN-γ did synergistically interact with acute restraint stress to increase plasma corticosterone concentrations, and this effect was most pronounced in the male mice. These data are among the first to show that systemically administered IFN-γ can alone or in conjunction with psychologically relevant stressor, modify brain regional monoamine activity and the plasma corticosterone response.

Responses of the mammary transcriptome of dairy cows to altered photoperiod during late gestation

Cows exposed to short day photoperiod (SD, 8L:16D) during the 60-day nonlactating period prior to parturition produce more milk in their subsequent lactation compared with cows exposed to long day photoperiod (LD, 16L:8D). Although this response is well established in dairy cows, the underlying mechanisms are not understood. We hypothesized that differential gene expression in cows exposed to SD or LD photoperiods during the dry period could be used to identify the functional basis for the subsequent increase in milk production during lactation. Pregnant, multiparous cows were maintained on an SD or LD photoperiod for 60 days prior to parturition. Mammary biopsies were obtained on days -24 and -9 relative to parturition and Affymetrix GeneChip Bovine Genome Arrays were used to quantify gene expression. Sixty-four genes were differentially expressed (P ≤ 0.05 and fold-change ≥ |1.5|) between SD and LD treatments. Many of these genes were associated with cell growth and proliferation, or immune function. Ingenuity Pathway Analysis predicted upstream regulators to include TNF, TGF-β1, interferon-γ, and several interleukins. In addition, expression of 125 genes was significantly different between day -24 and day -9; those genes were associated with milk component metabolism and immune function. The interaction of photoperiod and time affected 32 genes associated with insulin-like growth factor I signaling. Genes differentially expressed in response to photoperiod were associated with mammary development and immune function consistent with the enhancement of milk yield in the ensuing lactation. Our results provide insight into the mechanisms by which photoperiod affects the mammary gland and subsequently lactation.

Tumour necrosis factor alpha, interferon gamma and substance P are novel modulators of extrapituitary prolactin expression in human skin

Human scalp skin and hair follicles (HFs) are extra-pituitary sources of prolactin (PRL). However, the intracutaneous regulation of PRL remains poorly understood. Therefore we investigated whether well-recognized regulators of pituitary PRL expression, which also impact on human skin physiology and pathology, regulate expression of PRL and its receptor (PRLR) in situ. This was studied in serum-free organ cultures of microdissected human scalp HFs and skin, i.e. excluding pituitary, neural and vascular inputs. Prolactin expression was confirmed at the gene and protein level in human truncal skin, where its expression significantly increased (p = 0.049) during organ culture. There was, however, no evidence of PRL secretion into the culture medium as measured by ELISA. PRL immunoreactivity (IR) in female human epidermis was decreased by substance P (p = 0.009), while neither the classical pituitary PRL inhibitor, dopamine, nor corticotropin-releasing hormone significantly modulated PRL IR in HFs or skin respectively. Interferon (IFN) γ increased PRL IR in the epithelium of human HFs (p = 0.044) while tumour necrosis factor (TNF) α decreased both PRL and PRLR IR. This study identifies substance P, TNFα and IFNγ as novel modulators of PRL and PRLR expression in human skin, and suggests that intracutaneous PRL expression is not under dopaminergic control. Given the importance of PRL in human hair growth regulation and its possible role in the pathogenesis of several common skin diseases, targeting intracutaneous PRL production via these newly identified regulatory pathways may point towards novel therapeutic options for inflammatory dermatoses.

Neuroendocrine-immune correlates of circadian physiology: studies in experimental models of arthritis, ethanol feeding, aging, social isolation, and calorie restriction

Virtually all neuroendocrine and immunological variables investigated in animals and humans display biological periodicity. Circadian rhythmicity is revealed for every hormone in circulation as well as for circulating immune cells, lymphocyte metabolism and transformability, cytokines, receptors, and adhesion molecules. Clock genes, notably the three Period (Per1/Per2/Per3) genes and two Cryptochrome (Cry1/Cry2) genes, are present in immune and endocrine cells and are expressed in a circadian manner in human cells. This review discusses the circadian disruption of hormone release and immune-related mechanisms in several animal models in which circulating cytokines are modified including rat adjuvant arthritis, social isolation in rats and rabbits and alcoholism, the aging process and calorie restriction in rats. In every case the experimental manipulation used perturbed the temporal organization by affecting the shape and amplitude of a rhythm or by modifying the intrinsic oscillatory mechanism itself.

Role of prophet of Pit1 (PROP1) in gonadotrope differentiation and puberty

The prophet of Pit1 (PROP1) gene is essential for normal gonadotropin production in both humans and mice. Transgenic mice that overexpress PROP1 in gonadotropes and thyrotropes have transient hypogonadotropic hypogonadism and increased risk of pituitary adenomas. Here we report a temporal study of pituitary gonadotrope terminal differentiation and hypogonadism, delayed onset of puberty, and transient growth insufficiency in the transgenic males. The Prop1 transgenic mice recover from their abnormalities and exhibit normal size and fertility at 3 months. The relatively normal expression pattern of GnRH receptor (Gnrhr) suggests that the pituitary gonadotrope cell lineage is appropriately specified, but the ability to synthesize LH and FSH is impaired by excess PROP1. We report no obvious abnormalities in expression of the transcription factors early growth response 1, NR5A1, GATA2, TBX19, and NR0B1, or the TGFbeta pathway members including activin, inhibin, and activin receptors. Thus, overexpression of PROP1 may influence gonadotrope development by a novel mechanism. Microarray analysis identified the inhibitory transmembrane receptor gene Klrg1 and the protease gene Prss28 as candidates for involvement in this process. We hypothesize that variation in PROP1 expression could affect the growth spurt and the onset of puberty in humans.