Chronic Lithium Treatment Enhances the Number of Quiescent Neural Progenitors but Not the Number of DCX-Positive Immature Neurons

Background:

The term adult neurogenesis constitutes a series of developmental steps including the birth, survival, differentiation, maturation, and even death of newborn progenitor cells within neurogenic niches. Within the hippocampus progenitors reside in the neurogenic niche of the subgranular zone in the dentate gyrus subfield. At the different stages, designated type-I, type-IIa, type-IIb, type-III, and granule cell neurons, the cells express a series of markers enabling their identification and visualization. Lithium has been shown to increase hippocampal cell proliferation in the subgranular zone of the hippocampal dentate gyrus subfield of adult rodents and to stimulate the proliferation of hippocampal progenitor cells in vitro, but data regarding lithium’s ability to increase neuronal differentiation and survival is equivocal.

Methods:

To clarify the effect of lithium on adult hippocampal neurogenesis, we identified the effect of chronic lithium treatment on distinct stages of hippocampal progenitor development using adult Nestin-green fluorescent protein transgenic mice and immunofluorescent techniques.

Results:

The present observations confirm that lithium targets the initial stages of progenitor development enhancing the turnover of quiescent neural progenitors/putative stem-cells, corroborating previous reports. However, the enhanced quiescent neural progenitor-turnover does not translate into an increased number of immature neurons. We also observed a steep decline in the number of type-III immature neurons with complex tertiary-dendrites, suggesting that lithium alters the morphological maturation of newborn neurons.

Conclusions:

Our results do not corroborate previous reports of lithium-induced enhanced numbers of newly generated neurons.     

Deleting the BAFF receptor TACI protects against systemic lupus erythematosus without extensive reduction of B cell numbers

B cell-activating factor of the TNF family (BAFF) is an essential B cell survival factor. However, high levels of BAFF promote systemic lupus erythematosus (SLE) in mice and humans. Belimumab (anti-human BAFF) limits B cell survival and is approved for use in patients with SLE. Surprisingly, the efficacy of rituximab (anti-human CD20) in SLE remains controversial, despite depleting B cells more potently than belimumab. This raises the question of whether B cell depletion is really the mechanism of action of belimumab. In BAFF transgenic mice, SLE development is T cell-independent but relies on innate activation of B cells via TLRs, and TLR expression is modulated by the BAFF receptor TACI. Here, we show that loss of TACI on B cells protected against BAFF-mediated autoimmune manifestations while preserving B cells, suggesting that loss of BAFF signaling through TACI rather than loss of B cells may underpin the effect of belimumab in the clinic. Therefore, B cell-sparing blockade of TACI may offer a more specific and safer therapeutic alternative to broad B cell depletion in SLE.     

Islet amyloid polypeptide in the islets of Langerhans: friend or foe?

Islet amyloid polypeptide (IAPP), or amylin, was originally discovered as the constituent peptide in amyloid occurring in human insulinomas and in pancreatic islets in human subjects with Type II (non-insulin-dependent) diabetes mellitus. Its normal expression in beta cells and its co-secretion with insulin in response to nutrient stimuli, suggest a metabolic function for the peptide. Specifically, IAPP has most frequently been shown to inhibit insulin secretion, implying that IAPP has a role in the regulation of islet hormone homeostasis. The physiological significance of IAPP in islets has been difficult to assess; very high IAPP concentrations are required to alter insulin secretion. Moreover, until recently, IAPP receptors have not been characterised at the molecular level, thus leaving the actual target cells for IAPP unidentified. Furthermore, in experimental diabetes in rodents, the ratio of IAPP expression to that of insulin invariably is increased. In view of the pleiotropic effects attributed to IAPP, such regulation could be both adverse and beneficial in diabetes. Metabolic characterisation of mice carrying a null mutation in the IAPP gene or which overexpress IAPP in beta cells have recently confirmed that IAPP is a physiological inhibitor of insulin secretion. Based on experiments in which IAPP-deficient mice develop a more severe form of alloxan-induced diabetes, we argue that the action of IAPP in the islets normally is beneficial for beta-cell function and survival; thus, the established up regulation of IAPP expression compared with that of insulin in experimental rodent diabetes could serve to protect islets under metabolically challenging circumstances. [Diabetologia (2000) 43: 687–695]     

Interleukin-18 overproduction exacerbates the development of colitis with markedly infiltrated macrophages in interleukin-18 transgenic mice

BACKGROUND AND AIM: The authors have previously shown that production of interleukin (IL)-18 was increased in the inflamed mucosa of patients with Crohn's disease (CD) and blockade of IL-18 ameliorated the murine model of CD. This demonstrated that IL-18 plays a significant role during intestinal inflammation. However, the initial role of IL-18 during intestinal inflammation was unclear; therefore the susceptibility of IL-18 transgenic (Tg) mice to acute dextran sulfate sodium (DSS)-induced colitis was examined. METHODS: Interleukin-18 Tg and wild-type (WT) mice were fed 2.0% of DSS for 8 days. The total clinical scores (bodyweight loss, stool consistency, and rectal bleeding), colon length and histological scores were assessed. The expressions of surface markers and IL-18 on infiltrating lamina propria mononuclear cells were analyzed immunohistochemistrically. Mesenteric lymph node (MLN) cells were isolated and the expressions of CD4+ T-cell activation markers (CD69, CD25 and IL18R) were analyzed by flow cytometry. RESULTS: The IL-18 Tg mice exhibited an increased susceptibility to DSS-induced colitis, as shown by significantly increased clinical, histological scores, and more severe colonic shortening compared with WT mice. Immunohistochemical analysis revealed a significant increase of IL-18 production and CD11b+ macrophages but not CD4+ T cells in the inflamed mucosa in DSS-fed IL-18 Tg compared with DSS-fed WT mice. Furthermore, MLN cells revealed no evidence of increased CD4+ T-cell activation in DSS-fed IL-18 Tg. CONCLUSIONS: These findings suggest that IL-18 overproduction in the mucosa plays an important role in the marked infiltration of macrophages and exacerbates colitis in IL-18 Tg mice.     

HBV转基因小鼠暴露ATB-1后肝脏ATB-1-DNA加成物水平的测定

目的探讨ＨＢＶ与ＡＴＢ１协同致肝癌的机理．方法用ＲＩＡ法测定ＨＢＶ转基因小鼠与正常小鼠暴露ＡＴＢ１后０，０５，１，２，４，８，２４ｈ７个不同时相肝脏ＡＴＢ１ＤＮＡ加成物的含量变化．结果暴露ＡＴＢ１后，ＨＢＶ转基因小鼠肝脏ＡＴＢ１ＤＮＡ加成物含量在各时相均高于正常小鼠，尤以１ｈ高峰时相值（５５９２ｐｍｏｌ／ｍｇ±４１５ｐｍｏｌ／ｍｇ比４１３６ｐｍｏｌ／ｍｇ±２８２ｐｍｏｌ／ｍｇＤＮＡ，Ｐ＜００１）及２４ｈ时相值（２４８７±２０３比９８９±８５，Ｐ＜００１）最显著．２４ｈ后，转基因小鼠肝脏ＡＴＢ１ＤＮＡ加成物仍维持高水平，但正常小鼠已基本恢复至暴露前水平．结论ＨＢＶ转基因小鼠暴露ＡＴＢ１后肝脏ＡＴＢ１ＤＮＡ加成物含量增加可能为ＨＢＶ与ＡＴＢ１协同致肝癌的直接原因．     

HBsAg基因修饰的树突状细胞诱导HBV转基因小鼠的免疫应答

目的探讨HBsAg重组腺病毒Ad—S转染的小鼠树突状细胞（DC）诱导HBV转基因（Tg）小鼠免疫应答的作用特点及其可能的治疗作用。方法Tg小鼠的骨髓细胞体外扩增为DC，转染Ad—S或被HBsAg蛋白冲击后，与pcDNA3．1（＋）-S质粒分别免疫Tg鼠，用流式细胞术、乳酸脱氢酶释放法、酶联免疫分析（ELISA），荧光定量聚合酶链反应（PCR）等分别检测脾脏T细胞内细胞因子和细胞毒性T淋巴细胞（CTL）活性、血清HBsAg，抗-HBs、HBVDNA及丙氨酸转氨酶（ALT）水平；病理和免疫组化分析肝脏组织学及HBsAg和HBcAg表达。结果免疫后1～2周，DC／Ad-S比DC／HBsAg和pcDNA3．1（＋）-S诱导rrc分泌干扰素7（IFN-g）和特异性CTL均显著增强，而DC／HBsAg组CTL较pcDNA3．1（＋）-S组增强（P〈0．05）；DC／HBsAg免疫后1、2、4周CTL迅速减弱，DC／Ad-S在1、2周CTL差异不明显，但至4周时明显减弱。免疫后1～4周，对Tg鼠血清HBsAg、HBVDNA及肝组织HBcAg和HBsAg表达的抑制作用最强为DC／Ad-S免疫，其次为DC／HBsAg，显著强于pcDNA3．1（＋）-S（P〈0．05或P〈0．01）。肝脏组织学、血清抗-HBs和ALT水平各组差异无统计学意义。结论Ad—S转染的DC比HBsAg冲击的DC和DNA疫苗诱导更强的Tcl和CTL应答，能较迅速抑制HBV转基因小鼠血清HBsAg、HBVDNA和肝脏HBcAg和HBsAg表达。     

Overexpressed growth hormone (GH) synergistically promotes carcinogen‐initiated liver tumour growth by promoting cellular proliferation in emerging hepatocellular neoplasms in female and male GH‐transgenic mice

Abstract: Background/Aims: Growth hormone (GH), when overexpressed in male and female GH‐transgenic mice, is known to induce liver tumours within 1 year. This study aimed to gain a clearer understanding of the interaction between GH and tumour cells in vivo. Methods/Results: The carcinogen diethylnitrosomine (DEN) was administered to neo‐natal transgenic and non‐transgenic mice maintained in a “hepatocarcinogenesis resistant” genetic background (C57BL/6J). Macroscopic, microscopic and liver weight/body weight ratio analyses revealed that carcinogen‐induced hepatocarcinogenesis was dramatically accelerated in young GH‐transgenic mice compared to non‐transgenic counterparts. Image analysis of microscopic hepatocellular neoplasms showed rapidly increasing tumour burdens, and neoplastic foci size over time in young adult GH‐transgenic mice. The magnitude of enhanced tumour growth was equivalent in both male and female transgenic mice, whereas much lower and sexually dimorphic tumour growth rates (males>females) were observed in non‐transgenic mice treated with DEN. BrdU labelling experiments demonstrated that rapid tumour growth in carcinogen‐treated GH‐transgenic mice was due to the promotion of cell proliferation in emerging lesions. Tumour cell proliferation in young GH‐transgenic mice was 2.6‐ and 4‐fold higher, respectively, than that observed in similar age male and female non‐transgenic mice. Interestingly, both GH‐transgenic and non‐transgenic mice displayed progressively slower tumour growth rates in older animals. Conclusion: Overall, GH synergistically promotes carcinogen‐induced hepatocarcinogenesis in both sexes of GH‐transgenic mice by stimulating tumour cell proliferation.     

Recipient Myd88 Deficiency Promotes Spontaneous Resolution of Kidney Allograft Rejection

The myeloid differentiation protein 88 (MyD88) adapter protein is an important mediator of kidney allograft rejection, yet the precise role of MyD88 signaling in directing the host immune response toward the development of kidney allograft rejection remains unclear. Using a stringent mouse model of allogeneic kidney transplantation, we demonstrated that acute allograft rejection occurred equally in MyD88-sufficient (wild-type [WT]) and MyD88^−/− recipients. However, MyD88 deficiency resulted in spontaneous diminution of graft infiltrating effector cells, including CD11b⁻Gr-1⁺ cells and activated CD8 T cells, as well as subsequent restoration of near-normal renal graft function, leading to long-term kidney allograft acceptance. Compared with T cells from WT recipients, T cells from MyD88^−/− recipients failed to mount a robust recall response upon donor antigen restimulation in mixed lymphocyte cultures ex vivo. Notably, exogenous IL-6 restored the proliferation rate of T cells, particularly CD8 T cells, from MyD88^−/− recipients to the proliferation rate of cells from WT recipients. Furthermore, MyD88^−/− T cells exhibited diminished expression of chemokine receptors, specifically CCR4 and CXCR3, and the impaired ability to accumulate in the kidney allografts despite an otherwise MyD88-sufficient environment. These results provide a mechanism linking the lack of intrinsic MyD88 signaling in T cells to the effective control of the rejection response that results in spontaneous resolution of acute rejection and long-term graft protection.