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Zonis S, Pechnick RN, Ljubimov VA, Mahgerefteh M, Wawrowsky K, Michelsen KS, Chesnokova V. Chronic intestinal inflammation alters hippocampal neurogenesis. J Neuroinflammation 2015; 12:65. [PMID: 25889852 PMCID: PMC4403851 DOI: 10.1186/s12974-015-0281-0] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 03/11/2015] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Adult neurogenesis in the subgranular zone of the hippocampus is involved in learning, memory, and mood control. Decreased hippocampal neurogenesis elicits significant behavioral changes, including cognitive impairment and depression. Inflammatory bowel disease (IBD) is a group of chronic inflammatory conditions of the intestinal tract, and cognitive dysfunction and depression frequently occur in patients suffering from this disorder. We therefore tested the effects of chronic intestinal inflammation on hippocampal neurogenesis. METHODS The dextran sodium sulfate (DSS) mouse model of IBD was used. Mice were treated with multiple-cycle administration of 3% wt/vol DSS in drinking water on days 1 to 5, 8 to 12, 15 to 19, and 22 to 26. Mice were sacrificed on day 7 (acute phase of inflammation) or day 29 (chronic phase of inflammation) after the beginning of the treatment. RESULTS During the acute phase of inflammation, we found increased plasma levels of IL-6 and TNF-α and increased expression of Iba1, a marker of activated microglia, accompanied by induced IL-6 and IL-1β, and the cyclin-dependent kinase inhibitor p21(Cip1) (p21) in hippocampus. During the chronic phase of inflammation, plasma levels of IL-6 were elevated. In the hippocampus, p21 protein levels were continued to be induced. Furthermore, markers of stem/early progenitor cells, including nestin and brain lipid binding protein (BLBP), and neuronal marker doublecortin (DCX) were all down-regulated, whereas glial fibrillary acidic protein (GFAP), a marker for astroglia, was induced. In addition, the number of proliferating precursors of neuronal lineage assessed by double Ki67 and DCX staining was significantly diminished in the hippocampus of DSS-treated animals, indicating decreased production of new neurons. CONCLUSIONS We show for the first time that chronic intestinal inflammation alters hippocampal neurogenesis. As p21 arrests early neuronal progenitor proliferation, it is likely that p21 induction during acute phase of inflammation resulted in the reduction of hippocampal neurogenesis observed later, on day 29, after the beginning of DSS treatment. The reduction in hippocampal neurogenesis might underlie the behavioral manifestations that occur in patients with IBD.
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Affiliation(s)
- Svetlana Zonis
- Department of Medicine, Cedars-Sinai Medical Center, Davis Bldg., Room 3019, 8700 Beverly Blvd., Los Angeles, CA, 90048, USA.
| | - Robert N Pechnick
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA, 91766, USA.
| | - Vladimir A Ljubimov
- Department of Medicine, Cedars-Sinai Medical Center, Davis Bldg., Room 3019, 8700 Beverly Blvd., Los Angeles, CA, 90048, USA.
| | - Michael Mahgerefteh
- Department of Medicine, Cedars-Sinai Medical Center, Davis Bldg., Room 3019, 8700 Beverly Blvd., Los Angeles, CA, 90048, USA.
| | - Kolja Wawrowsky
- Department of Medicine, Cedars-Sinai Medical Center, Davis Bldg., Room 3019, 8700 Beverly Blvd., Los Angeles, CA, 90048, USA.
| | - Kathrin S Michelsen
- F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.
| | - Vera Chesnokova
- Department of Medicine, Cedars-Sinai Medical Center, Davis Bldg., Room 3019, 8700 Beverly Blvd., Los Angeles, CA, 90048, USA.
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Zonis S, Ljubimov VA, Mahgerefteh M, Pechnick RN, Wawrowsky K, Chesnokova V. p21Cip restrains hippocampal neurogenesis and protects neuronal progenitors from apoptosis during acute systemic inflammation. Hippocampus 2013; 23:1383-94. [PMID: 23966332 DOI: 10.1002/hipo.22192] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 11/06/2022]
Abstract
Altered neurogenesis in adult hippocampus is implicated in cognition impairment and depression. Inflammation is a potent inhibitor of neurogenesis. The cyclin-dependent kinase inhibitor p21(Cip1) (p21) restrains cell cycle progression and arrests the cell in the G1 phase. We recently showed that p21 is expressed in neuronal progenitors and regulates proliferation of these cells in the subgranular zone of the dentate gyrus of hippocampus where adult neurogenesis occurs. The current study suggests that p21 is induced in vivo in the hippocampus of WT mice in response to acute systemic inflammation caused by LPS injections, restrains neuronal progenitor proliferation and protects these cells from inflammation-induced apoptosis. In intact p21-/- hippocampus, neuronal progenitors proliferate more actively as assessed by BrdU incorporation, and give rise to increased number of DCX positive neuroblasts. However, when mice were treated with LPS, the number of neuroblasts decreased due to induced subgranular zone apoptosis. In vitro, differentiating Tuj-1 positive neuroblasts isolated from p21-/- hippocampus exhibited increased proliferation rate, measured by Ki-67 staining, as compared to WT cells (p<0.05). In WT neuronal progenitors treated with IL-6, the number of p21-positive cells was increased (p<0.05), and this led to Tuj-1(+) cell proliferation restraint, whereas the number of proliferating GFAP(+) astrocytes was increased ~ 2-fold. Thus, when p21 is intact, inflammation might divert neuronal progenitors towards astrogliogenesis by inducing p21. At the same time, when p21 is lacking, no effects of IL-6 on proliferation of Tuj-1(+) cells or GFAP(+) cells are detected in differentiating p21-/- neuronal progenitors. These results underscore the important role of p21 controlling hippocampal neuronal differentiation during inflammation.
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Affiliation(s)
- Svetlana Zonis
- Department of Medicine, Division of Endocrinology, Cedars-Sinai Medical Center, Los Angeles, CA
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