Perioperative steroids
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Manual of Neuroanesthesia, 2017
Steroids are generally given when there is alteration in the steroid regulation of synthesis. So there are many tests that are developed for assessment of the hypothalamic–pituitary–adrenal (HPA) axis. They are as follows: Single measurement of serum cortisol and urinary free cortisolRandom cortisol estimationShort Synacthen test (SST)Insulin tolerance test (ITT)Corticotropin-releasing hormone (CRH) testOvernight metyrapone testGlucagon stimulation test
Testosterone signaling in spermatogenesis, male fertility and infertility
Rajender Singh in Molecular Signaling in Spermatogenesis and Male Infertility, 2019
Testicular Leydig cells synthesize the male sex steroid hormones, which are low molecular weight compounds derived from cholesterol, under the regulation of LH. While Leydig cells are capable of de novo synthesis of cholesterol from acetyl coenzyme A, the main source of cholesterol comes from lipoprotein particles transported through the blood into the Leydig cells. Steroid synthesis commences with the transportation of cytosolic cholesterol from the outer membrane to the inner membrane of the mitochondria, which also serves as the rate-limiting step in the process of steroidogenesis. A number of proteins assist in the transportation of the hydrophobic cholesterol, which is unable to simply diffuse through the membrane on its own. The most important of these proteins is the steroidogenic acute regulatory protein StAR (4), consisting of a family of 37 kDa (precursor) and 30 kDa (mature) mitochondrial proteins (5). It mainly detects the response of Leydig cells against tropic hormones and other external stimuli and helps in transporting free cholesterol inside mitochondria of the Leydig cells, stimulating steroidogenesis.
Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Sheryl S. Smith in Neurosteroid Effects in the Central Nervous System, 2003
The first, rate-limiting, and hormonally regulated step in the synthesis of all steroid hormones is the conversion of cholesterol to pregnenolone (Figure 1.1). This reaction is catalyzed by the mitochondrial enzyme cholesterol side chain cleavage, P450scc, in three successive chemical reactions: 20α -hydroxylation, 22-hydroxylation, and scission of the c20–c22 carbon bond cholesterol. These three reactions occur on a single active site that is in contact with the hydrophobic bilayer membrane. The products of this reaction are pregnenolone and isocaproic acid. Homozygous deletion of the gene for P450scc in the rabbit eliminates all steroidogenesis,5,6 confirming that all steroidogenesis is initiated by this single enzyme, including the brain.7,8 Homozygous inactivation of P450scc is probably incompatible with human fetal development, and haploinsufficiency of P450scc due to heterozygous mutation causes a lateonset form of congenital lipoid adrenal hyperplasia.9
Human ovarian granulosa cells use clathrin-mediated endocytosis for LDL uptake: immunocytochemical and electron microscopic study
Published in Ultrastructural Pathology, 2023
Aynur Abdulova, Merjem Purelku, Hakan Sahin, Gamze Tanrıverdi
Steroidogenesis is a complex process between multiple enzymes and substrates by which cholesterol is converted into steroid hormones. Cholesterol is stored in lipid droplets (LDs) as cholesterol esters (CEs) within the steroidogenic tissue. The cholesterol that is required for steroidogenesis which is being initiated in response to a hormonal stimulus is provided by the mobilization of these stored CEs within the cells.3 There are two different forms of cholesterol which are known as high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Studies are focused on the fact that granulosa cells use the LDL-receptor (LDLR)-mediated endocytic pathway for steroid biosynthesis. LDLR is an important protein that functions to mediate the uptake of LDL cholesterol, which is a specific substrate for steroid hormone production.3–5 Many different endocytic pathways have been described in eukaryotic cells, but the main pathway for LDL transport has been reported to be the clathrin-mediated endocytosis pathway.6,7 However, no study that clarifies LDL internalization in human granulosa cells and whether the clathrin-mediated endocytic pathway is functional in this process has yet been published.
Oxytocin modulates steroidogenesis-associated genes and estradiol levels in the placenta
Published in Systems Biology in Reproductive Medicine, 2023
Sung-Min An, Min Jae Kim, Jea Sic Jeong, So Young Kim, Da Som Kim, Beum-Soo An, Seung Chul Kim
Steroid hormones are primarily produced by a biological process called steroidogenesis, which is the process by which cholesterol is converted into several other steroid hormones. Humans and various mammals use cholesterol to synthesize steroid hormones in the reproductive glands and placenta (Payne and Hales 2004). During pregnancy, multiple steroid hormones released by the placenta perform a variety of roles, including placental trophoblast differentiation, expansion and maturation of the placental vessels, and uterine endovascular invasion by the placental trophoblast (extravillous cytotrophoblast) (Pepe and Albrecht 2008). One study demonstrated that CTB isolated form human placentas are capable of differentiating and fusing spontaneously to form functional STB as well as producing steroid hormones (Kliman et al. 1986). In addition, various studies have conducted research on synthesis of steroid hormones using JEG-3 cells (Samson et al. 2009; Cao et al. 2017; Karahoda et al. 2021). Since the process of synthesizing steroid hormones in the placenta has a large impact on the mother and fetus during pregnancy, in-depth studies on placental steroidogenesis are inevitable.
Proteomic profiling of RAW264.7 macrophage cells exposed to graphene oxide: insights into acute cellular responses
Published in Nanotoxicology, 2019
Xiaoliang Yang, Yan Zhang, Wenjia Lai, Zhichu Xiang, Bin Tu, Dan Li, Xiaohui Nan, Chunying Chen, Zhiyuan Hu, Qiaojun Fang
Figure 5(B) shows that the up-regulated proteins were also significantly over-represented in the ‘hematopoietic cell lineage’ and ‘steroid biosynthesis’ pathways, based on the results from all three analysis methods. The ‘hematopoietic cell lineage’ pathway reflects the development of blood cells from a hematopoietic stem cell in the immune response. RAW 264.7 cell is one type of myeloid cell that can undergo acute phase response and be activated upon stimulation. As shown in Figure 6(B,C), the increase in the mRNA levels of C-reactive protein (Crp), Tnfα, and Il-6, together with the changes in cell morphology and aggregation, confirmed the acute phase response and activation of cells after GO treatment. FDFT1 which increased by 1.73-fold and MSMO1 by 1.35-fold are involved in steroid biosynthesis. The steroid biosynthesis pathway is an anabolic pathway that produces steroids from simple precursors. Steroids and their metabolites can function as signal molecules and components of the cell membrane. Three proteins – ITGB2 (average ratio: 1.37), ITGAM (average ratio: 1.52), and ATP6V0A1 (average ratio: 1.35) – are related to phagocytosis in the phagosome pathway and the tuberculosis pathway. Phagosome formation is crucial for tissue homeostasis and for both innate and adaptive host defense against stimulations. The phagosome vesicles containing GO increased in a GO concentration-dependent manner (Figure 6(D)), as confirmed by the TEM images of the cells.
Related Knowledge Centers
- Animal
- Membrane Fluidity
- Organic Compound
- Signal Transduction
- Sterol
- Cell Membrane
- Bile
- Cholesterol
- Bicyclic Molecule
- Molecular Configuration