Effects of Tumor Necrosis Factor .ALPHA. and Interferon .GAMMA. on the Viability and mRNA Expression of TNF Receptor Type I in Endothelial Cells from the Bovine Corpus Luteum

Abstract

Abstract. The corpus luteum (CL) is mainly composed of luteal steroidogenic cells (LSCs) and luteal endothelial cells (LECs). Cell death of LSCs and LECs is essential for structural luteolysis. Therefore, it is important to understand the mechanisms regulating cell death in both types of luteal cells. We previously reported that a treatment combining tumor necrosis factor α (TNF) and interferon γ (IFNG) induced cell death in LSCs and that LECs express TNF receptor type I (TNFRI). To investigate the mechanism of cell death in LECs, in the present study we determined the effects of the same cytokines on cell viability and TNFRI mRNA expression in cultured LECs. To induce cell death in LECs, LECs were treated with TNF or IFNG (0, 0.05, 0.5, 1.0, 2.5 nM) and a combination of TNF (0.5 nM) and IFNG (0.5 nM) for 24 h. The viability of LECs was reduced by a single treatment with TNF or IFNG dose-dependently (P<0.05). Cell viability was further decreased by treatment with a combination of TNF and IFNG (P<0.05). Cells with DNA fragmentation (TUNEL-positive cells) were observed after the treatment with TNF and IFNG. Semi-quantitative RT-PCR analysis revealed that treatment with IFNG alone or in combination with TNF increased the expression of TNFRI mRNA compared with the control (P<0.05). In summary, TNF and IFNG increased cell death in cultured bovine LECs. The upregulation of TNFRI mRNA expression by IFNG suggests that TNF and IFNG synergistically affect the death of LECs resulting in acute luteolysis. Key words: Bovine, Cell death, Corpus luteum, Luteal endothelial cell, Luteolysis (J. Reprod. Dev. 56: [515][516][517][518][519] 2010) he corpus luteum (CL) is a transient organ that forms from the wall of a Graafian follicle following ovulation and secretes progesterone (P4) [1]. It reaches structural and functional maturity by the mid luteal phase and then begins to regress after Day 17 postovulation of a non-fertile cycle. In cows, luteal regression is characterized by a reduction in P4 production (functional luteolysis) and tissue degeneration by apoptosis (structural luteolysis) [2,3].Development of the bovine CL is associated with intensive angiogenesis [4], so that the mature CL becomes one of the most highly vascularized organs in the body [5][6][7], and vascular endothelial cells account for up to 50% of the total cells of the mid CL [8,9]. Recently, capillaries without smooth muscle and a few blood vessels with smooth muscle were found in the center of the mid bovine CL [10], and we reported that the capillaries disappeared, but not the large blood vessels during luteolysis [11]. Luteal endothelial cells (LECs) are the first cells to undergo programmed cell death (apoptosis) during luteal regression, resulting in the loss of capillaries [12,13].The number of leukocytes in the bovine CL (e.g., T lymphocytes, macrophages) increases at the time of luteolysis [14], and leukocytes are known to produce a variety of cytokines, including tumor necrosis factor α (TNF) and interferon γ (IFNG). A combination of IFNG and ...

Programmed necrosis - a new mechanism of steroidogenic luteal cell death and elimination during luteolysis in cows

“…Furthermore, although type I IFNs, such as IFN α and β, can stimulate necroptosis in cancer cells and macrophages4748, a single treatment with IFNG also did not affect RIPKs mRNA expression in bovine LSCs. IFNG induces expression of TNF superfamily receptors in several cells104950 including bovine LSCs7, and the combination of TNF and IFNG can stimulate acute apoptosis and luteolysis71051. Based on the above findings, we hypothesized that TNF in combination with IFNG can stimulate RIPK-dependent cell death.…”

“…Apoptosis occurs through two main signaling cascades, namely, the extrinsic apoptotic route and intrinsic apoptotic cascade1415. Some studies have revealed that TNF and IFNG strongly stimulate the extrinsic apoptotic route via stimulating several cytokine receptors, such as TNFRI and FAS, in bovine LSCs67910. Furthermore, another major apoptotic pathway, the intrinsic apoptotic cascade, is regulated by members of the Bcl-protein family, which is composed of antiapoptotic ( e.g ., Bcl-2) and proapoptotic ( e.g ., Bax) proteins41552.…”

“…Generally, caspase-dependent apoptosis, also known as type I programmed cell death5, in the cells that form the CL, such as luteal steroidogenic cells (LSC) and luteal endothelial cells (LEC), is thought to be the predominant pathway for cell death during luteolysis in several species including cattle34. A large number of factors have been implicated in structural and functional regression of bovine CL67891011. Apoptosis of luteal cells and CL vascular regression are regulated/modulated by pro-inflammatory cytokines, i.e., tumor necrosis factor-α (TNF), interferon-γ (IFNG), FAS ligand (FASL) and nitric oxide (NO)678910.…”

“…A large number of factors have been implicated in structural and functional regression of bovine CL67891011. Apoptosis of luteal cells and CL vascular regression are regulated/modulated by pro-inflammatory cytokines, i.e., tumor necrosis factor-α (TNF), interferon-γ (IFNG), FAS ligand (FASL) and nitric oxide (NO)678910. On the other hand, P4, cortisol and luteotropic PGs (PGE2 and PGI2) protect LSCs against apoptosis111213.…”

“…During the past several decades, apoptosis is considered to be the most studied local mechanism regulating structural luteolysis of the bovine CL. Thus, a great number of studies have been focused on type-I programmed cell death of steroidogenic and accessory luteal cells678910111213. However, luteolysis, especially exogenous PGF-induced luteolysis, is a very rapid process and the bovine CL completely disappears from the ovary within 2 days after PGF injection.…”