SalmonellaEnteritidis Infection Slows Steroidogenesis and Impedes Cell Growth in Hen Granulosa Cells

Abstract

Infection by Salmonella Enteritidis (SE) causes decreased egg production in laying hens. Immunoresponse, steroidogenesis, and cell proliferation by chicken granulosa cells (cGCs) are of particular interest because these changes are involved in follicular growth, atresia, and ovulation. To elucidate the possible mechanisms underlying these changes, transcriptional alterations in cGCs at distinct stages of follicular maturity were studied. Luteinizing hormone (LH)-and follicle-stimulating hormone (FSH) were applied to the cGCs isolated from hierarchical and prehierarchical follicles, respectively, to imitate the effects of gonadotropin during in vitro SE infection. Results showed that the expression of Toll-like receptor 15 was dependent on the follicular maturity, with mature cells having a more significant and progressively stronger immunoresponse. Attenuated responses to LH and FSH as well as retardant steroidogenesis due to down-regulated LH receptor, FSH receptor, and the P450 side-chain cleavage system were observed and may have led to delayed hierarchical follicular growth. Deteriorated cell viability of prehierarchical follicles may occur, as the proliferation of stimulator heparin-binding epidermal growth factor was reduced significantly. Furthermore, the infection led to a higher probability of cGCs from the smaller follicles undergoing apoptosis than those from F1 follicles. Collectively, the data provide evidence of a tendency toward pathogen elimination in F1 follicles by induction of a strong immune response and cell apoptosis in smaller follicles to avoid bacterial transovarian infection. It is our speculation that slowed steroidogenesis and impeded follicular growth may play essential roles in decreased ovulation rate as well as further decreased egg production during SE infection.

The impact ofSalmonellaEnteritidis on lipid accumulation in chicken hepatocytes

“…Therefore, a further in vivo study is needed to support the observation. Our previous studies revealed that SE infection negatively affects steroidogenesis, cell proliferation of granulosa cells from the prehierarchical and hierarchical follicles, and innate immune function (Tsai et al, 2010;Wang et al, 2013aWang et al, , 2014. The results of this study consistently revealed that SE infection may not only cause abnormal hepatic lipid metabolism, but also diminish lipoprotein deposition.…”

“…Salmonella enterica serovar Enteritidis ATCC 13076 (American Type Culture Collection, Manassas, VA, USA) was used in this study and has previously been characterized in studies of the interactions between SE and egg production (Wang et al, 2013a(Wang et al, , 2014. Bacteria were cultured in brain heart infusion broth (Difco, Detroit, MI, USA) at 37°C for 18 h, and then centrifuged (5 min, 1500 × g).…”

“…intestine, liver, spleen, lung, ovary, and oviduct) (Hoop & Pospischil, 1993). Infection with SE increases chick mortality and disrupts egg formation to reduce egg production in laying hens without obvious clinical signs (Shivaprasad et al, 1990;Wang et al, 2014). SE can be recovered from 53% of chicken liver, and SE can persist in the liver as a chronic infection for up to 5 weeks after oral inoculation of Leghorn hens (Gast & Holt, 2000).…”

“…Results of our previous studies indicated that infection with SE retards steroidogenesis of chicken ovarian granulosa cells ex vivo. The resultant decrease in progesterone production may be the cause of decreased egg production in hens infected with SE (Wang et al, 2013a(Wang et al, , 2014. Lipid metabolism in the liver has also been regarded as having an important role in egg maturation and production.…”

Genetic Basis of Salmonella Enteritidis Pathogenesis in Chickens

“…The age, sexual maturation, and differential expression of immune mediators are suspected as potential underlying factors (Anastasiadou et al, 2013;Ebers et al, 2009;Withanage et al, 2003). This may also partially explain the differential susceptibility of ovarian follicles at different maturation stages (Wang et al, 2014). Thus, it is imperative to establish a standardized in vitro cell culture system to study interaction between SE and the avian RT, which may also serve as a model to study other relevant avian pathogens (e.g., avian coronavirus infectious bronchitis virus) with RT tissue tropism (Mork et al, 2014).…”