International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.

Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist

The John Hughes Memorial Lecture: aspects of sperm physiology-oxidative stress and the functionality of stallion spermatozoa

Spermatozoa are vulnerable to oxidative attack because they contain an abundance of polyunsaturated fatty acids that are susceptible to lipid peroxidation. In addition, functionally important proteins and DNA are also subject to oxidative modification and adduction by aldehydes, such as 4-hydroxynonenal (4HNE), generated as a consequence of the peroxidative process. The proteins adducted by 4HNE include elements of the mitochondrial electron transport chain, such as succinic acid dehydrogenase. The net result of such electrophilic attack is to stimulate generation of mitochondrial reactive oxygen species (ROS) in a self-perpetuating lipid peroxidation–ROS generation cycle that ultimately triggers the intrinsic apoptotic pathway, leading to a rapid loss of motility and cell death. A major point of difference between apoptosis in spermatozoa and somatic cells is that in the former, nuclear DNA is located in a compartment (the head) separate from the mitochondria and most of the cytoplasm (the midpiece). As a result, nucleases activated and released in the midpiece during apoptosis cannot gain access to the DNA in the sperm head in order to cleave the DNA. However, the ROS generated during apoptosis can readily gain access to the sperm nucleus and generate oxidative base adducts, typically 8-hydroxy, 2′-deoxyguanosine (8OHdG), which are converted into abasic sites by 8-oxoguanine glycosylase (OGG1), the only enzyme of the base excision repair pathway possessed by spermatozoa. These abasic sites subsequently become the foci of DNA fragmentation. Because defective sperm function and DNA damage are frequently associated with oxidative stress, there is a great deal of interest in the use of antioxidants in a therapeutic context. This presentation examines the fundamental relationships between oxidative stress and sperm function and considers the implications of recent findings for the management of sperm function and fertility in stallions

Capacitation in the presence of methyl-β-cyclodextrin results in enhanced zona pellucida-binding ability of stallion spermatozoa

While IVF has been widely successful in many domesticated species, the development of a robust IVF system for the horse remains an elusive and highly valued goal. A major impediment to the development of equine IVF is the fact that optimised conditions for the capacitation of equine spermatozoa are yet to be developed. Conversely, it is known that stallion spermatozoa are particularly susceptible to damage arising as a consequence of capacitation-like changes induced prematurely in response to semen handling and transport conditions. To address these limitations, this study sought to develop an effective system to both suppress and promote the in vitro capacitation of stallion spermatozoa. Our data indicated that the latter could be achieved in a bicarbonate-rich medium supplemented with a phosphodiesterase inhibitor, a cyclic AMP analogue, and methyl-β-cyclodextrin, an efficient cholesterol-withdrawing agent. The populations of spermatozoa generated under these conditions displayed a number of hallmarks of capacitation, including elevated levels of tyrosine phosphorylation, a reorganisation of the plasma membrane leading to lipid raft coalescence in the peri-acrosomal region of the sperm head, and a dramatic increase in their ability to interact with heterologous bovine zona pellucida (ZP) and undergo agonist-induced acrosomal exocytosis. Furthermore, this functional transformation was effectively suppressed in media devoid of bicarbonate. Collectively, these results highlight the importance of efficient cholesterol removal in priming stallion spermatozoa for ZP binding in vitro