Establishment of SLC7A11-knockout mouse and its preliminary investigation in melanoma

Solute carrier family 7 member 11 (SLC7A11)/xCT is an amino acid transporter that mediates the cystine uptake and glutamate export, participates in several malignant tumors' progression. However, the role of SLC7A11 on the occurrence and development of melanoma still remains unclear. Here, the transcribed mRNA encoding for Cas9 and sgRNA targeting SLC7A11 in vitro were microinjected into zygotes, to establish the SLC7A11 knockout (KO) mice (SLC7A11-/-). Further, we conducted melanoma-bearing mice using the metastatic melanoma cell line (B16-F10) to observe the melanoma development. There was no off-target in KO mice detected by T7E1 cleavage assay. The results showed that the tumor volume of KO mice was significantly lower than that of SLC7A11+/+ (WT) mice at 8d, 10d, 12d, 14d, and 16d (P < 0.05). The tumors of WT appeared to more disorganized morphology, more unbalanced nuclear-cytoplasmic ratio, less defined boundary, and increased tumor necrosis. And after SLC7A11 deletion, the expression of CXCL9 and TLR6 were significantly up-regulated, and that of NOS2 and CCL8 were significantly down-regulated (P < 0.01). Additionally, Ki67 immunostaining revealed lower proliferating cells in the tumors of SLC7A11 KO mice compared to WT mice. In summary, the deletion of SLC7A11 significantly inhibited the development of melanoma. Our results provide direct evidence to identify SLC7A11 as a novel target for molecular therapy and prognosis judgment of melanoma.

Redox Regulation of Microglial Inflammatory Response: Fine Control of NLRP3 Inflammasome through Nrf2 and NOX4

The role of inflammation and immunity in the pathomechanism of neurodegenerative diseases has become increasingly relevant within the past few years. In this context, the NOD-like receptor protein 3 (NLRP3) inflammasome plays a crucial role in the activation of inflammatory responses by promoting the maturation and secretion of pro-inflammatory cytokines such as interleukin-1β and interleukin-18. We hypothesized that the interplay between nuclear factor erythroid 2-related factor 2 (Nrf2) and NADPH oxidase 4 (NOX4) may play a critical role in the activation of the NLRP3 inflammasome and subsequent inflammatory responses. After priming mixed glial cultures with lipopolysaccharide (LPS), cells were stimulated with ATP, showing a significant reduction of IL1-β release in NOX4 and Nrf2 KO mice. Importantly, NOX4 inhibition using GKT136901 also reduced IL-1β release, as in NOX4 KO mixed glial cultures. Moreover, we measured NOX4 and NLRP3 expression in wild-type mixed glial cultures following LPS treatment, observing that both increased after TLR4 activation, while 24 h treatment with tert-butylhydroquinone, a potent Nrf2 inducer, significantly reduced NLRP3 expression. LPS administration resulted in significant cognitive impairment compared to the control group. Indeed, LPS also modified the expression of NLRP3 and NOX4 in mouse hippocampus. However, mice treated with GKT136901 after LPS impairment showed a significantly improved discrimination index and recovered the expression of inflammatory genes to normal levels compared with wild-type animals. Hence, we here validate NOX4 as a key player in NLRP3 inflammasome activation, suggesting NOX4 pharmacological inhibition as a potent therapeutic approach in neurodegenerative diseases.

Knockout of IL-6 mitigates cold water-immersion restraint stress-induced intestinal epithelial injury and apoptosis

Background

Interleukin-6 (IL-6) is essential for maintaining intestinal epithelial homeostasis. Although cold water-immersion restraint (CWIR) stress is commonly used to induce in vivo gastric injury, it also affects intestinal epithelial permeability. Although IL-6 is increased in response to acute physiological and psychological stress, its exact effects on the pathophysiology of the intestinal epithelium in response to acute CWIR stress remain unknown.

Methods

We used IL-6 knockout (KO) mice with acute CWIR modeling to investigate the effect of IL-6 deficiency on intestinal epithelial morphology and pathological damage using histological staining assays under the acute stress. We detected jejunal epithelial apoptosis using TUNEL and standard molecular experiments.

Results

CWIR caused intestinal epithelial damage, which was alleviated by the absence of IL-6, as evidenced by morphological changes and goblet cell and intestinal permeability alteration. IL-6 KO also reduced CWIR-mediated inflammatory levels and improved stress defense. Meanwhile, IL-6 deficiency decreased the intestinal epithelial apoptosis induced by CWIR administration. This IL-6 KO-led effect depended more on mitochondrial AIF signaling rather than the traditional caspase pathway.

Conclusion

As a result, we concluded that acute CWIR-induced severe intestinal damage and jejunal epithelium apoptosis could be alleviated by IL-6 deficiency, implying a protective effect of IL-6 deficiency on the intestines under acute stress. The findings shed new light on treating CWIR-induced intestinal disorders by inhibiting IL-6 signaling.

CXCL5 inhibits excessive oxidative stress by regulating white adipocyte differentiation

Chemokines have been well-documented as a major factor in immune cell migration and the regulation of immune responses. However, recent studies have reported that chemokines have diverse roles, both in immune cells and other cell types, including adipocytes. This study investigated the molecular functions of C-X-C motif chemokine ligand 5 (CXCL5) in white adipose cells using Cxcl5 knock-out (KO) mice fed a high-fat diet (HFD). The expression of Cxcl5 decreased by 90% during adipocyte differentiation and remained at a low level in mature adipocytes. Moreover, adipogenesis was enhanced when adipocytes were differentiated from the stromal vascular fraction (SFV) of Cxcl5 KO mice. Feeding an HFD increased the generation of reactive oxygen species (ROS) and promoted abnormal adipogenesis in Cxcl5 KO mice. Oxidative stress and insulin resistance occurred in Cxcl5 KO mice due to decreased antioxidant enzymes and failure to remove ROS. These results indicate the principal roles of CXCL5 in adipogenesis and ROS regulation in adipose tissue, further suggesting that CXCL5 is a valuable chemokine for metabolic disease research.

The Hippo Pathway Effectors YAP and TAZ Regulate LH Release by Pituitary Gonadotrope Cells in Mice

The Hippo transcriptional coactivators YAP and TAZ exert critical roles in morphogenesis, organ size determination and tumorigenesis in many tissues. Although Hippo kinase cascade activity was recently reported in the anterior pituitary gland in mice, the role of the Hippo effectors in regulating gonadotropin production remains unknown. The objective of this study was therefore to characterize the roles of YAP and TAZ in gonadotropin synthesis and secretion. Using a conditional gene targeting approach (cKO), we found that gonadotrope-specific inactivation of Yap and Taz resulted in increased circulating levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in adult male mice, along with increased testosterone levels and testis weight. Female cKO mice had increased circulating LH (but not FSH) levels, which were associated with a hyperfertility phenotype characterized by higher ovulation rates and larger litter sizes. Unexpectedly, the loss of YAP/TAZ did not appear to affect the expression of gonadotropin subunit genes, yet both basal and GnRH-induced LH secretion were increased in cultured pituitary cells from cKO mice. Likewise, pharmacologic inhibition of YAP binding to the TEAD family of transcription factors increased both basal and GnRH-induced LH secretion in LβT2 gonadotrope-like cells in vitro without affecting Lhb expression. Conversely, mRNA levels of ChgA and SgII, which encode key secretory granule cargo proteins, were decreased following pharmacologic inhibition of YAP/TAZ, suggesting a mechanism whereby YAP/TAZ regulate the LH secretion machinery in gonadotrope cells. Together, these findings represent the first evidence that Hippo signaling may play a role in regulating pituitary LH secretion.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Ablation of All Synaptobrevin vSNAREs Blocks Evoked But Not Spontaneous Neurotransmitter Release at Neuromuscular Synapses

Synaptic transmission occurs when an action potential triggers neurotransmitter release via the fusion of synaptic vesicles with the presynaptic membrane, driven by the formation of SNARE complexes composed of the vesicular (v)-SNARE synaptobrevin and the target (t)-SNAREs Snap-25 and syntaxin-1. Neurotransmitters are also released spontaneously, independent of an action potential, through the fusion of synaptic vesicles with the presynaptic membrane. The major neuronal vSNAREs, synaptobrevin-1 and synaptobrevin-2, are expressed at the developing neuromuscular junction (NMJ) in mice, but their specific roles in NMJ formation and function remain unclear. Here, we examine the NMJs in mutant mouse embryos lacking either synaptobrevin 1 (Syb1^lew/lew ) or synaptobrevin 2 (Syb2 ^-/-), and those lacking both (Syb1^lew/lewSyb2 ^-/-). We found that, compared with controls: (1) the number and size of NMJs was markedly increased in Syb2 ^-/- and Syb1^lew/lewSyb2 ^-/- mice, but not in Syb1^lew/lew mice; (2) synaptic vesicle density was markedly reduced in Syb1^lew/lewSyb2 ^-/- NMJs; and (3) evoked neurotransmission was markedly reduced in Syb2 ^-/- NMJs and completely abolished in Syb1^lew/lewSyb2 ^-/- NMJs. Surprisingly, however, spontaneous neurotransmission persists in the absence of both Syb1 and Syb2. Furthermore, spontaneous neurotransmission remains constant in Syb1^lew/lewSyb2 ^-/- NMJs despite changing Ca²⁺ levels. These findings reveal an overlapping role for Syb1 and Syb2 (with Syb2 being dominant) in developing NMJs in mice. Moreover, because spontaneous release becomes Ca²⁺-insensitive in Syb1^lew/lewSyb2 ^-/- NMJs, our findings suggest that synaptobrevin-based SNARE complexes play a critical role in conferring Ca²⁺ sensitivity during spontaneous release.SIGNIFICANCE STATEMENT Neurotransmitters can be released at synapses with (evoked) or without (spontaneous) the influence of action potentials. Whereas evoked neurotransmission requires Ca²⁺ influx, those underlying the spontaneous neurotransmission may occur with or without Ca²⁺ Our findings show that, in the absence neuronal vSNARE synaptobrevin-1 and synaptobrevin-2, evoked neurotransmission is completely abolished; however, spontaneous synaptic transmission not only persists but even increased. Furthermore, spontaneous synaptic transmission that is normally highly Ca²⁺-sensitive became Ca²⁺-independent upon deletion of vSNARE synaptobrevin-1 and synaptobrevin-2. These findings reveal distinct mechanisms for evoked and spontaneous neurotransmitter release. Moreover, these findings suggest that synaptobrevin-based SNARE complexes play critical roles in conferring Ca²⁺ sensitivity during spontaneous neurotransmission at developing neuromuscular synapses in mice.

Targeting Phospholipase D Genetically and Pharmacologically for Studying Leukocyte Function

Phospholipase D (PLD), is a protein that breaks down phospholipids, maintaining structural integrity and remodeling of cellular or intracellular membranes, as well as mediating protein trafficking and cytoskeletal dynamics during cell motility. One of the reaction products of PLD action is phosphatidic acid (PA). PA is a mitogen involved in a large variety of physiological cellular functions, such as cell growth, cell cycle progression, and cell motility. We have chosen as cell models the leukocyte polymorphonuclear neutrophil and the macrophage as examples of cell motility. We provide a three-part method for targeting PLD genetically and pharmacologically to study its role in cell migration. In the first part, we begin with genetically deficient mice PLD1-KO and PLD2-KO. We describe bone marrow neutrophil (BMN) isolation; BMN is labeled fluorescently and can be used for studying tissue-damaging neutrophilia in ischemia-reperfusion injury (IRI). In the second part, we begin also with PLD1-KO and PLD2-KO and prepare bone marrow-derived macrophages (BMDM), first from monocytes and then inducing macrophage differentiation in culture with continuous incubation of cytokines. We use BMDM to find experimentally if PLD woul play a role in cholesterol phagocytosis, which is the first step in atherosclerosis progression. In the third part, we study PLD function in BMN and BMDM with PLD enzyme pharmacological inhibitors instead of genetically deficient mice, to ascertain the particular contributions of isoforms PLD1 and PLD2 on leukocyte function. By using the three-step thorough approach, we could understand the molecular underpinning of PLD in the pathological conditions indicated above, IRI-neutrophilia and atherosclerosis.

Estradiol regulates AQP2 expression in the collecting duct: a novel inhibitory role for estrogen receptor α

While there is evidence that sex hormones influence multiple systems involved in salt and water homeostasis, the question of whether sex hormones regulate aquaporin-2 (AQP2) and thus water handling by the collecting duct has been largely ignored. Accordingly, the present study investigated AQP2 expression, localization and renal water handling in intact and ovariectomized (OVX) female rats, with and without estradiol or progesterone replacement. OVX resulted in a significant increase in urine osmolality and increase in p256-AQP2 in the renal cortex at 7 days post-OVX, as well as induced body weight changes. Relative to OVX alone, estradiol repletion produced a significant increase in urine output, normalized urinary osmolality and reduced both total AQP2 (protein and mRNA) and p256-AQP2 expression, whereas progesterone repletion had little effect. Direct effects of estradiol on AQP2 mRNA and protein levels were further tested in vitro using the mpkCCD principal cell line. Estradiol treatment of mpkCCD cells reduced AQP2 at both the mRNA and protein level in the absence of deamino-8-d-AVP (dDAVP) and significantly blunted the dDAVP-induced increase in AQP2 at the protein level only. We determined that mpkCCD and native mouse collecting ducts express both estrogen receptor (ER)α and ERβ and that female mice lacking ERα displayed significant increases in AQP2 protein compared with wild-type littermates, implicating ERα in mediating the inhibitory effect of estradiol on AQP2 expression. These findings suggest that changes in estradiol levels, such as during menopause or following reproductive surgeries, may contribute to dysregulation of water homeostasis in women.

Behavioral characterization of striatal-enriched protein tyrosine phosphatase (STEP) knockout mice

Striatal-enriched protein tyrosine phosphatase (STEP) has been described as a regulator of multiple kinases and glutamate receptor subunits critical for synaptic plasticity. Published behavioral and biochemical characterization from the founder line of STEP knockout (KO) mice revealed superior cognitive performance, with enhanced phosphorylation of substrates such as ERK, Fyn and GluN2B; suggesting that inhibitors of STEP may have potential as therapeutic agents for the treatment of neuropsychiatric disorders. The objectives of this work aimed to replicate and extend the previously reported behavioral consequences of STEP knockout. Consistent with previous reported data, STEP KO mice demonstrated exploratory activity levels and similar motor coordination relative to WT littermate controls as well as intact memory in a Y-maze spatial novelty test. Interestingly, KO mice demonstrated deficits in pre-pulse inhibition as well as reduced seizure threshold relative to WT controls. Immunohistochemical staining of brains revealed the expected gene-dependent reduction in STEP protein confirming knockout in the mice. The present data confirm expression and localization of STEP and the absence in KO mice, and describe functional downstream implications of reducing STEP levels in vivo.

Osteopontin is an initial mediator of inflammation and liver injury during obstructive cholestasis after bile duct ligation in mice

Osteopontin (OPN) is a chemotactic factor which can be cleaved to the pro-inflammatory form by matrix metalloproteinases (MMPs). To test the hypothesis that OPN can modulate inflammatory liver injury during cholestasis, wild-type (WT) C57BL/6 and OPN knockout (OPN-KO) mice underwent bile duct ligation (BDL). OPN-KO mice showed significant reduction in liver injury (plasma ALT and necrosis) and neutrophil recruitment compared with WT animals at 24h but not 72h after BDL. In WT mice, a 4-fold increase in hepatic MMP-3 mRNA and elevated MMP activities and cleaved OPN levels were observed in bile. WT mice subjected to BDL in the presence of the MMP inhibitor BB-94 showed reduced liver injury, less neutrophil extravasation and diminished levels of cleaved OPN in bile. Thus, during obstructive cholestasis, OPN released from biliary epithelial cells could be cleaved by MMPs in bile. When the biliary system leaks, cleaved OPN enters the parenchyma and attracts neutrophils. In the absence of OPN, other chemoattractants, e.g. chemokines, mediate a delayed inflammatory response and injury. Taken together, our data suggest that OPN is the pro-inflammatory mediator that initiates the early neutrophil-mediated injury phase during obstructive cholestasis in mice.

The role of melanin-concentrating hormone and its receptors in energy homeostasis

Extensive studies in rodents with melanin-concentrating hormone (MCH) have demonstrated that the neuropeptide hormone is a potent orexigen. Acutely, MCH causes an increase in food intake, while chronically it leads to increased weight gain, primarily as an increase in fat mass. Multiple knockout mice models have confirmed the importance of MCH in modulating energy homeostasis. Animals lacking MCH, MCH-containing neurons, or the MCH receptor all are resistant to diet-induced obesity. These genetic and pharmacologic studies have prompted a large effort to identify potent and selective MCH receptor antagonists, initially as tool compounds to probe pharmacology in models of obesity, with an ultimate goal to identify novel anti-obesity drugs. In animal models, MCH antagonists have consistently shown efficacy in reducing food intake acutely and inhibiting body-weight gain when given chronically. Five compounds have proceeded into clinical testing. Although they were reported as well-tolerated, none has advanced to long-term efficacy and safety studies.