Protective effects of the salt-induced kinase inhibitor HG-9-91-01 on sepsis-associated cognitive dysfunction in mice and the underlying mechanisms / 中南大学学报(医学版)

Objective:Sepsis-associated cognitive dysfunction is a common complication in patients with sepsis and lack of effective treatment.Its pathological mechanisms remain unclear.Salt-induced kinase(SIK)is an important molecule in the regulation of metabolism,immunity,and inflammatory response.It is associated with the development of many neurological diseases.This study aims to investigate the expression of SIK in the hippocampus of septic mice,and to evaluate the role and mechanism of the SIK inhibitor HG-9-91-01 in sepsis-associated cognitive dysfunction. Methods:Firstly,C57BL/6 mice were randomly divided into a control group(Con group)and a sepsis model group[lipopolysaccharide(LPS)group].The model group was injected intraperitoneally with LPS at a dose of 8 mg/kg and the Con group was injected with an equal volume of normal saline.Hippocampal tissues were harvested at 1,3,and 6 days after injection and the expressions of SIK1,SIK2,and SIK3 were detected by real-time fluorescence quantitative PCR(qPCR)and Western blotting.Secondly,C57BL/6 mice were randomly divided into a Con group,a LPS group,and a SIK inhibitor group(HG group).The LPS and HG groups were injected with LPS to establish a sepsis model;in the HG group,HG-9-91-01(10 mg/kg)was injected intraperitoneally at 3-6 days after LPS injection,and the LPS group was injected with the same volume of vehicle.Cognitive function was assessed at 7-11 days after LPS injection using the Morris water maze(MWM).Hippocampal tissues were harvested after the behavioral tests,and the mRNA levels of inflammatory factors and microglial markers were assessed by qPCR.The protein levels of inducible nitric oxide synthase(iNOS),CD68,ionized calcium binding adaptor molecule 1(Iba-1),N-methyl-D-aspartate(NMDA)receptor(NR)subunit,cAMP response element-binding protein(CREB)-regulated transcription coactivator 1(CRTC1),and insulin-like growth factor 1(IGF-1)were detected by Western blotting.Immunohistochemistry(IHC)was used to detect the expression of Iba-1 positive cells in the CA1,CA3 and dentate gyrus(DG)of the hippocampus,followed by Sholl analysis. Results:Compared with the Con group,the mRNA and protein levels of SIK1,SIK2,and SIK3 in the hippocampus were increased in the LPS group(all P<0.05).Compared with the Con group,mice in the LPS group had a significantly longer escape latency,a lower percentage of target quadrant dwell time and a reduced locomotor speed(all P<0.05);the HG group had a decreased escape latency and an increased percentage of time spent in the target quadrant in comparison with the LPS group(both P<0.05).The mRNA levels of inflammatory factors[tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β),interleukin-6(IL-6)],and the M1-type microglial markers iNOS and CD68 in the hippocampus of the LPS group were increased in comparison with the Con group,while the M2-type microglial markers CD206 and arginase-1(Arg-1)were decreased.Compared with the LPS group,the mRNA levels of TNF-α,IL-1β,IL-6,and iNOS were downregulated,while the levels of CD206 and Arg-1 were upregulated in the HG group(all P<0.05).The protein levels of iNOS,CD68,and Iba-1 in the hippocampus of the LPS group were increased in comparison with the Con group,but they were downregulated in the HG group in comparison with the LPS group(all P<0.05).The number of Iba-1 positive cells in CA1,CA3,and DG of the hippocampus was increased in the LPS group in comparison with the Con group,but they were decreased in the HG group in comparison with the LPS group(all P<0.05).Sholl analysis showed that the number of intersections at all radii between 8-38 μm from the microglial soma was decreased in the LPS group in comparison with the Con group(all P<0.05).Compared with the LPS group,the number of intersections at all radii between 14-20 μm was significantly increased in the HG group(all P<0.05).The protein levels of NR subunit NR1,NR2A,NR2B,and IGF-1 were downregulated in the hippocampus of the LPS group in comparison with the Con group,while the expression of phosphorylated CRTC1(p-CRTC1)was increased.Compared with the LPS group,the levels of NR1,NR2A,NR2B,and IGF-1 were upregulated,while p-CRTC1 was downregulated in the HG group(all P<0.05). Conclusion:SIK expression is upregulated in the hippocampus of septic mice.The SIK inhibitor HG-9-91-01 ameliorates sepsis-associated cognitive dysfunction in mice,and the mechanism may involve in the activation of the CRTC1/IGF-1 pathway,inhibition of neuroinflammation,and enhancement of synaptic plasticity.

Salt-inducible kinase 2 regulates energy metabolism in rats with cerebral ischemia-reperfusion / 浙江大学学报·医学版

To investigate the effects of salt-inducible kinase 2 (SIK2) on energy metabolism in rats with cerebral ischemia-reperfusion. Adult SD male rats were divided into 5 groups: sham group, ischemia group, reperfusion group, adenovirus no-load group, and SIK2 overexpression group with 5 animals in each group. The middle cerebral artery occlusion (MCAO) was induced with the modified Zea-Longa line thrombus method to establish the cerebral ischemia reperfusion model. Eight days before the MCAO, SIK2 overexpression was induced by injecting 7 μL adenovirus in the right ventricle, then MCAO was performed for followed by reperfusion HE staining was used to observe the pathological changes of cerebral tissue in rats; TTC staining was used to observe the volume of cerebral infarct. The levels of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) in rat brain tissue were detected by ELISA; the levels of SIK2 and hypoxia-inducible factor 1α (HIF-1α) in the rat brain tissues were detected by RT-qPCR and Western blotting. Compared with the sham group, SIK2 level was decreased in the ischemia group, and it was further declined in the reperfusion group (<0.05). Compared with the sham group and ischemic group, the pathological injury in reperfusion group were more severe, and the infarct size was larger; compared with the reperfusion group and adenovirus no-load group, the pathological injury of the SIK2 overexpression group was milder, and the infarct size is less. Compared with the sharn group, HIF-1α was increased in both ischemia group and reperfusion group, especially in ischemia group (all <0.05); HIF-1α level in the SIK2 overexpression group was higher than that in the reperfusion group and adenovirus no-load group (all <0.05). ATP level in ischemia group and reperfusion group was lower than that in the sham group, and the reperfusion group decreased more significantly than the ischemia group (<0.05); ADP content was increased in the ischemia and reperfusion group, and the ADP content in reperfusion group was significantly higher than that in the ischemia group (<0.05). ATP level in the SIK2 overexpression group was higher than that in the reperfusion group and adenovirus no-load group (all <0.05), and ADP was decreased in the SIK2 overexpression group (all <0.05). SIK2 can up-regulate the ATP level and down-regulate the ADP level in rat brain tissue and alleviate cerebral ischemia-reperfusion injury by increase the level of HIF-1α.

Relationship between salt-inducible kinase 2 (SIK2) and lymph node metastasis in colorectal cancer patients complicated with chronic schistosomiasis / 浙江大学学报·医学版

To investigate the relationship between salt-inducible kinase 2 (SIK2) and lymph node metastasis in colorectal cancer patients complicated with chronic schistosomiasis. Tissue specimens were collected from 363 patients who were diagnosed as colorectal cancer by clinical and pathological examination in Wuhu Second People's Hospital from June 2015 to June 2020. Fifty-six patients were colorectal cancer complicated with schistosomiasis (CRC-S) and 307 patients were colorectal cancer not complicated with schistosomiasis (CRC-NS). The clinical and pathological data of the patients were analyzed to explore the relationship between chronic schistosomiasis and colorectal cancer. Immunohistochemistry and Western blotting were used to detect the distribution and expression of SIK2 in colorectal cancer specimens. The relationship between SIK2 and lymph node metastasis of CRC-S was analyzed. The rate of lymph node metastasis in CRC-S group was significantly higher than that in CRC-NS group (62.5% vs. 47.2%, <0.05). In CRC-S patients with lymph node metastasis, schistosome eggs were distributed mainly in tumor tissues (25/35, 71.4%), while in patients with CRC-S without lymph node metastasis, schistosome eggs were distributed mainly in paracancerous tissues (17/21, 81.0%) (14.243, <0.01). The SIK2 was mainly located in cytosol, and its expression in tumor tissues was higher than that in paracancerous tissues. Compared with CRC-NS patients, the expression of SIK2 in CRC-S patients was significantly increased; the expression of SIK2 in patients with lymph node metastasis was higher than that in patients without lymph node metastasis; and the expression of SIK2 in patients with schistosome eggs in cancer tissues was higher than that in patients with schistosome eggs in paracancerous tissues (all <0.01). Lymph node metastasis is more likely to be occurred in colorectal cancer patients with schistosomiasis, especially in those with schistosome eggs in tumor tissues. The expression of SIK2 may be correlated with chronic schistosomiasis, egg distribution and lymphatic metastasis.

Salt-induced kinase 1 and tumors / 国际肿瘤学杂志

Salt-inducible kinase 1 (SIK1) is closely related to tumorigenesis.The expressions of SIK1 in hepatocellular carcinoma,pancreatic cancer,gastric cancer,lung cancer,ovarian cancer and other tumors are specific,and their abnormal expressions can inhibit or promote the occurrence,development and metastasis of tumor.Abnormal expressions of SIK1 are expected to provide a new method for the diagnosis and treatment of tumors,and provide guidance for clinical prognosis.

Effect of salt-inducible kinase 2 on checkpoint in response to γ-ray irradiation / 中华放射医学与防护杂志

Objective To investigate the effect of salt-induced kinase 2 (SIK2) in the G2/M checkpoint in response to ionizing radiation and the possible mechanism.Methods HeLa cells were irradiated with 60Co γ-rays.The cell model of knockdown SIK2 expression was constrcuted by transfecting HeLa cells with a pSicoR-based lentivirus vector of expressing SIK2 shRNA by lipofectamin 2000.Western blot and flow cytometry were performed to measure the changes of SIK2 protein level and cell cycle distribution.The phosphorylated histone protein H3 on Ser 10 was used as a molecular marker of mitotic cells for detecting the function of G2/M checkpoint.Results The expression level of SIK2 protein increased in HeLa cells after 60Co γ-ray irradiation.A cell model of knockdown SIK2 expression was successfully generated by transfecting the specific shRNA against SIK2.Depression of SIK2 significantly increased the cellular sensitivity at 1,2,4,6 Gy post-irradiation (t =-3.445,-2.581,-3.251,-2.553,P ＜0.05),and led cells to release earlier from the G2/M boundary arrest compared to control cells at 5,6 h post-irradiation (t =4.341,6.500,P ＜ 0.05).Western blot analysis indicated that the irradiation-induced phosphorylated CHK2/T68 in SIK2 knock-down cells was earlier than that in control cells.Conclusions salt-induced kinase 2 (SIK2) participates in the regulation of G2/M checkpoint induced by ionizing radiation and affects cellular radiosensitivity.

Construction of recombinant plasmids and their overexpression of SIK2 cDNA and its truncated mutants / 西安交通大学学报(医学版)

Objective To construct recombinant plasmids of SIK2 cDNA and its truncated mutants and induce its expression in E.coil.Methods We designed primers of SIK2 and its truncated mutants.The gene fragments of SIK2,SIK2-Δ1 (280-926),SIK2-Δ2 (400-926),SIK2-Δ3 (1-400),and SIK2-Δ4 (700-926)were amplified by polymerase chain reaction (PCR)and cloned into pGEX-4T-2 vector to construct recombinant plasmids with GST. The plasmids were transformed into E.coil BL2 1 respectively,and induced with IPTG to express fusion protein. The results were confirmed by Coomassie blue staining and Western blot.Results We successfully constructed recombinant plasmid of SIK2 cDNA and its truncated mutants.Coomassie blue staining and Western blot resutls showed that these plasmids were induced to be expressed in E.coil BL21.Conclusion SIK2 cDNA and its truncated mutants were overexpressed in E.coil BL2 1 ,which lays expereimental foundation for further study on the function of each domain of SIK2 .