Mammary glands of Aly mice: developmental changes and lactation-related expression of specific proteins, alpha-casein, GLyCAM-1 and MAdCAM-1

The intestine: A highly dynamic microenvironment for IgA plasma cells

To achieve longevity, IgA plasma cells require a sophisticated anatomical microenvironment that provides cytokines, cell-cell contacts, and nutrients as well as metabolites. The intestinal epithelium harbors cells with distinct functions and represents an important defense line. Anti-microbial peptide-producing paneth cells, mucus-secreting goblet cells and antigen-transporting microfold (M) cells cooperate to build a protective barrier against pathogens. In addition, intestinal epithelial cells are instrumental in the transcytosis of IgA to the gut lumen, and support plasma cell survival by producing the cytokines APRIL and BAFF. Moreover, nutrients are sensed through specialized receptors such as the aryl hydrocarbon receptor (AhR) by both, intestinal epithelial cells and immune cells. However, the intestinal epithelium is highly dynamic with a high cellular turn-over rate and exposure to changing microbiota and nutritional factors. In this review, we discuss the spatial interplay of the intestinal epithelium with plasma cells and its potential contribution to IgA plasma cell generation, homing, and longevity. Moreover, we describe the impact of nutritional AhR ligands on intestinal epithelial cell-IgA plasma cell interaction. Finally, we introduce spatial transcriptomics as a new technology to address open questions in intestinal IgA plasma cell biology.

Preparation and Preliminary Application of MAdCAM-1 Polyclonal Antibody in Dairy Cows with Subclinical Mastitis

MAdCAM-1 plays an important role in mediating immune response and inflammation. This study aimed to express and purify a fusion protein of MAdCAM-1 in prokaryotic cells and to prepare rat anti-bovine MAdCAM-1 polyclonal antibodies. Prokaryotic expression vector pGEX-4T-1-MAdCAM-1 and pET-28a-MAdCAM-1 were constructed, respectively. The above plasmids were transformed into BL21 Escherichia coli strain. These recombinant strains were induced by IPTG and identified by Western blot analysis and SDS-PAGE. Wistar rats were immunized with recombinant protein (pET-28a-MAdCAM-1) emulsified with Freund's adjuvant, and antibody titers were measured by indirect ELISA. Antibody titers reached the highest value (1:128,000) after the third immunization. Western blot showed that rat anti-bovine MAdCAM-1 polyclonal antibody can not only recognize recombinant MAdCAM-1 protein expressed in E. coli but also recognizes natural MAdCAM-1 protein extracted from bovine tissues. However, commercial anti-mouse MAdCAM-1 monoclonal antibodies did not recognize the recombinant MAdCAM-1 protein or natural protein, which indicated no cross-reactivity between bovine MAdCAM-1 and mouse MAdCAM-1. Real-time fluorescence quantitative polymerase chain reaction and Western blot analysis showed that MAdCAM-1 expression was limited in mammary lymphoid nodes of subclinical mastitis in dairy cows. We speculate that MAdCAM-1 expression is inconsistent in different periods of the dairy cows. The successful preparation of rat anti-bovine MAdCAM-1 polyclonal antibody and its preliminary application in dairy cows provide the foundation for further study of the mechanism of anti-inflammation of MAdCAM-1 in dairy cows with subclinical mastitis.

The CD markers of camel (Camelus dromedarius) milk cells during mastitis: the LPAM-1 expression is an indication of possible mucosal nature of the cellular trafficking

Studying the cellular populations of the camel mammary glands through the expression pattern of the CD markers and adhesion molecules is a mean to define whether the cellular trafficking pathway is peripheral or mucosal nature. Camel milk cells from 8 Gram-positive and 5 Gram-negative infected camels were examined with flow cytometry using cross-reacting antibodies like, anti-CD4(+), CD8(+), WC+1(+)γδ, CD62L, CD11a(+)/CD18, LPAM-1, CXCR2. The overall results indicated high flow cytometry output of most of the CD makers. The statistical analysis of the mean percentage of the expressed CD markers has shown that CD62L, CXCR-2, LPAM-1, CD11a/CD18, CD8(+), IL-6R and CD20(+) were expressed in significant differences in either type of the infection. The LPAM-1 expression has provided further support to the notion that the lymphocyte trafficking is of the mucosal nature. The mucosal origin of cellular trafficking has important implications on the vaccine design and therapeutical approaches to mastitis.

Constitutive activation of nuclear factor-kappaB is preferentially involved in the proliferation of basal-like subtype breast cancer cell lines

Constitutive nuclear factor (NF)-kappaB activation is thought to be involved in survival, invasion, and metastasis in various types of cancers. However, neither the subtypes of breast cancer cells with constitutive NF-kappaB activation nor the molecular mechanisms leading to its constitutive activation have been clearly defined. Here, we quantitatively analyzed basal NF-kappaB activity in 35 human breast cancer cell lines and found that most of the cell lines with high constitutive NF-kappaB activation were categorized in the estrogen receptor negative, progesterone receptor negative, ERBB2 negative basal-like subtype, which is the most malignant form of breast cancer. Inhibition of constitutive NF-kappaB activation by expression of IkappaBalpha super-repressor reduced proliferation of the basal-like subtype cell lines. Expression levels of mRNA encoding NF-kappaB-inducing kinase (NIK) were elevated in several breast cancer cell lines, and RNA interference-mediated knockdown of NIK reduced NF-kappaB activation in a subset of the basal-like subtype cell lines with upregulated NIK expression. Taken together, these results suggest that constitutive NF-kappaB activation, partially dependent on NIK, is preferentially involved in proliferation of basal-like subtype breast cancer cells and may be a useful therapeutic target for this subtype of cancer.

Humoral and cellular factors of maternal immunity in swine

Immunoglobulins cannot cross the placenta in pregnant sows. Neonatal pigs are therefore agammaglobulinemic at birth and, although immunocompetent, they cannot mount rapid immune responses at systemic and mucosal sites. Their survival depends directly on the acquisition of maternal immunity via colostrum and milk. Protection by maternal immunity is mediated by a number of factors, including specific systemic humoral immunity, involving mostly maternal IgG transferred from blood to colostrum and typically absorbed within the first 36 h of life. Passive mucosal immunity involves local humoral immunity, including the production of secretory IgA (sIgA), which is transferred principally via milk until weaning. The mammary gland (MG) produces sIgA, which is, then secreted into the milk via the poly-Ig receptor (pIgR) of epithelial cells. These antibodies are produced in response to intestinal and respiratory antigens, including pathogens and commensal organisms. Protection is also mediated by cellular immunity, which is transferred via maternal cells present in mammary secretions. The mechanisms underlying the various immunological links between MG and the mucosal surfaces involve hormonally regulated addressins and chemokines specific to these compartments. The enhancement of colostrogenic immunity depends on the stimulation of systemic immunity, whereas the enhancement of lactogenic immunity depends on appropriate stimulation at induction sites, an increase in cell trafficking from the gut and upper respiratory tract to the MG and, possibly, enhanced immunoglobulin production at the effector site and secretion in milk. In addition, mammary secretions provide factors other than immunoglobulins that protect the neonate and regulate the development of mucosal immunity--a key element of postnatal adaptation to environmental antigens.

Molecular cloning and functional characterization of porcine CCL28: Possible involvement in homing of IgA antibody secreting cells into the mammary gland

Constitutive expression of chemokines by epithelial cells controls the recruitment and the localization of specialized lymphocytes. Mucosae associated-epithelial chemokine (MEC/CCL28) cloned from porcine salivary gland and colon tissues consisted of an open reading frame (ORF) of 384-bp coding for 127 amino-acids protein with 22 residues signal sequence. The resulting mature protein is composed of 105 aa with 4 conserved cysteine residues. CCL28 shows aa sequence identity with rat, mouse, macaque and human ranging from 67 to 87%. Using plasmid pQETris-CCL28 injection, a rabbit anti-serum was produced and showed a specific reactivity towards non-reduced form of CCL28 recombinant protein. Comparatively to CCL25 mRNA expression, RT-PCR analysis showed that CCL28 is expressed in various mucosal tissues, but most abundantly in nasal mucosa, colon, salivary and mammary gland (MG). Immunohistochemical analysis showed that CCL28 is produced by epithelial cells of these tissues suggesting that this chemokine can play an important role by linking homing mechanisms between the gut, nasal mucosa and MG. In addition, mRNA of CCL28 was up-regulated in the MG at late gestation and during lactation but was not found at weaning. CCL28 protein was excreted in sow's milk sustaining that this chemokine plays a key role of IgA-ASCs accumulation in this tissue and thus controls the passive transfer level of IgA antibodies from mother to infant.

RelB/p52 NF-kappaB complexes rescue an early delay in mammary gland development in transgenic mice with targeted superrepressor IkappaB-alpha expression and promote carcinogenesis of the mammary gland

Classical NF-kappaB (p65/p50) transcription factors display dynamic induction in the mammary gland during pregnancy. To further elucidate the role of NF-kappaB factors in breast development, we generated a transgenic mouse expressing the IkappaB-alpha S32/36A superrepressor (SR) protein under control of the mouse mammary tumor virus (MMTV) long terminal repeat promoter. A transient delay in mammary ductal branching was observed in MMTV-SR-IkappaB-alpha mice early during pregnancy at day 5.5 (d5.5) and d7.5; however, development recovered by mid- to late pregnancy (d14.5). Recovery correlated with induction of nuclear cyclin D1 and RelB/p52 NF-kappaB complexes. RelB/p52 complexes induced cyclin D1 and c-myc promoter activities and failed in electrophoretic mobility shift assay to interact with IkappaB-alpha-glutathione S-transferase, indicating that their weak interaction with IkappaB-alpha can account for the observed recovery of mammary gland development. Activation of IKKalpha and NF-kappaB-inducing kinase was detected by d5.5, implicating the alternative NF-kappaB signaling pathway in RelB/p52 induction. Constitutively active IKKalpha induced p52, RelB, and cyclin D1 in untransformed mammary epithelial cells. Moreover, mouse mammary tumors induced by 7,12-dimethylbenz(a)anthracene treatment displayed increased RelB/p52 activity. Inhibition of RelB in breast cancer cells repressed cyclin D1 and c-Myc levels and growth in soft agar. These results implicate RelB/p52 complexes in mammary gland development and carcinogenesis.

Cyclin D1 represses p300 transactivation through a cyclin-dependent kinase-independent mechanism

Cyclin D1 encodes a regulatory subunit, which with its cyclin-dependent kinase (Cdk)-binding partner forms a holoenzyme that phosphorylates and inactivates the retinoblastoma protein. In addition to its Cdk binding-dependent functions, cyclin D1 regulates cellular differentiation in part by modifying several transcription factors and nuclear receptors. The molecular mechanism through which cyclin D1 regulates the function of transcription factors involved in cellular differentiation remains to be clarified. The histone acetyltransferase protein p300 is a co-integrator required for regulation of multiple transcription factors. Here we show that cyclin D1 physically interacts with p300 and represses p300 transactivation. We demonstrated further that the interaction of the two proteins occurs at the peroxisome proliferator-activated receptor gamma-responsive element of the lipoprotein lipase promoter in the context of the local chromatin structure. We have mapped the domains in p300 and cyclin D1 involved in this interaction. The bromo domain and cysteine- and histidine-rich domains of p300 were required for repression by cyclin D1. Cyclin D1 repression of p300 was independent of the Cdk- and retinoblastoma protein-binding domains of cyclin D1. Cyclin D1 inhibits histone acetyltransferase activity of p300 in vitro. Microarray analysis identified a signature of genes repressed by cyclin D1 and induced by p300 that promotes cellular differentiation and induces cell cycle arrest. Together, our results suggest that cyclin D1 plays an important role in cellular proliferation and differentiation through regulation of p300.

Osteoclast differentiation is impaired in the absence of inhibitor of kappa B kinase alpha

Signaling through the receptor activator of nuclear factor kappa B (RANK) is required for both osteoclast differentiation and mammary gland development, yet the extent to which RANK utilizes similar signaling pathways in these tissues remains unclear. Mice expressing a kinase-inactive form of the inhibitor of kappa B kinase alpha (IKK alpha) have mammary gland defects similar to those of RANK-null mice yet have apparently normal osteoclast function. Because mice that completely lack IKK alpha have severe skin and skeletal defects that are not associated with IKK alpha-kinase activity, we wished to directly examine osteoclastogenesis in IKK alpha(-/-) mice. We found that unlike RANK-null mice, which completely lack osteoclasts, IKK alpha(-/-) mice did possess normal numbers of TRAP(+) osteoclasts. However, only 32% of these cells were multinucleated compared with 57% in wild-type littermates. A more profound defect in osteoclastogenesis was observed in vitro using IKK alpha(-/-) hematopoietic cells treated with colony-stimulating factor 1 and RANK ligand (RANKL), as the cells failed to form large, multinucleated osteoclasts. Additionally, overall RANKL-induced global gene expression was significantly blunted in IKK alpha(-/-) cells, including osteoclast-specific genes such as TRAP, MMP-9, and c-Src. IKK alpha was not required for RANKL-mediated I kappa B alpha degradation or phosphorylation of mitogen-activated protein kinases but was required for RANKL-induced p100 processing. Treatment of IKK alpha(-/-) cells with tumor necrosis factor alpha (TNF alpha) in combination with RANKL led to partial rescue of osteoclastogenesis despite a lack of p100 processing. However, the ability of TNF alpha alone or in combination with transforming growth factor beta to induce osteoclast differentiation was dependent on IKK alpha, suggesting that synergy between RANKL and TNFalpha can overcome p100 processing defects in IKK alpha(-/-) cells.

The donor splice site mutation in NFkappaB-inducing kinase of alymphoplasia (aly/aly) mice

The alymphoplasia (aly/aly) mouse has a spontaneous mutation maintained on a C57BL/6xAEJ ( H-2(b)) background that results in an absence of extrasplenic secondary lymphoid tissues. The cDNA defect has previously been shown to reside in a point mutation causing a G855R substitution in NFkappaB-inducing kinase (NIK). Since the aly/aly female cannot lactate, the strain must be bred by intercrossing heterozygous females with homozygous males and the offspring typed by serum IgA levels at the age of 4-6 weeks. We originally determined the genomic location of the alymphoplasia mutation by sequencing boundaries of regions homologous to human NIK exons, although recently the entire genomic sequence of murine C57BL/6 NIK has become available through the mouse genome project. The aly mutation is at position -1 of an intron donor consensus splice site. Exon-connexion PCR confirmed that splicing does occur across this site. Using the genomic information, we also developed a method of PCR typing of aly/aly mice from tail clips, and used this to derive an aly/aly muMT double-mutant strain in which antibody independent typing is essential. Genetic typing should considerably simplify husbandry and manipulation of the aly/aly genetic background, which is widely used as a recipient in lymphocyte transfer experiments to permit examination of the relative role of secondary lymphoid structures in immune responses.

IKKalpha provides an essential link between RANK signaling and cyclin D1 expression during mammary gland development

To identify functions of the IKKalpha subunit of IkappaB kinase that require catalytic activity, we generated an Ikkalpha(AA) knockin allele containing alanines instead of serines in the activation loop. Ikkalpha(AA/AA) mice are healthy and fertile, but females display a severe lactation defect due to impaired proliferation of mammary epithelial cells. IKKalpha activity is required for NF-kappaB activation in mammary epithelial cells during pregnancy and in response to RANK ligand but not TNFalpha. IKKalpha and NF-kappaB activation are also required for optimal cyclin D1 induction. Defective RANK signaling or cyclin D1 expression results in the same phenotypic effect as the Ikkalpha(AA) mutation, which is completely suppressed by a mammary specific cyclin D1 transgene. Thus, IKKalpha is a critical intermediate in a pathway that controls mammary epithelial proliferation in response to RANK signaling via cyclin D1.

Regulation of glycosylation-dependent cell adhesion molecule 1 (GlyCAM-1) gene in the mouse mammary gland differs from that of casein genes

Mouse glycosylation-dependent cell adhesion molecule 1 (GlyCAM-1), also known as mC26 and homologous to bovine PP3, is a milk protein synthesized in the mammary gland. Several studies have investigated the regulation of casein, the major milk protein, gene in the mammary gland, but little is known about GlyCAM-1. Here we examined GlyCAM-1 gene expression in mouse mammary epithelial cells. First, we detected GlyCAM-1 expression in mammary epithelial cells in situ by immunohistochemistry; almost all mammary epithelial cells of the lactating mouse expressed GlyCAM-1. Second, mammary epithelial cells were digested with collagenase and cultured with insulin, prolactin and/or glucocorticoid. alpha-Casein and beta-casein genes were expressed following treatment with insulin, prolactin and glucocorticoid. In contrast, GlyCAM-1 expression could not be detected with any combination of these three hormones. We also analyzed changes in the levels of GlyCAM-1 and caseins mRNAs in cultured cells. The addition of hormones to the culture medium increased casein mRNAs, but surprisingly reduced GlyCAM-1 mRNA. Our results suggest that the mechanisms that regulate GlyCAM-1 gene in mammary cells of lactating mice are different from those involved in the regulation of casein genes.