MANF protein expression is upregulated in immune cells in the ischemic human brain and systemic recombinant MANF delivery in rat ischemic stroke model demonstrates anti-inflammatory effects

Mesencephalic astrocyte-derived neurotrophic factor (MANF) has cytoprotective effects on various injuries, including cerebral ischemia, and it can promote recovery even when delivered intracranially several days after ischemic stroke. In the uninjured rodent brain, MANF protein is expressed almost exclusively in neurons, but post-ischemic MANF expression has not been characterized. We aimed to investigate how endogenous cerebral MANF protein expression evolves in infarcted human brains and rodent ischemic stroke models. During infarct progression, the cerebral MANF expression pattern both in human and rat brains shifted drastically from neurons to expression in inflammatory cells. Intense MANF immunoreactivity took place in phagocytic microglia/macrophages in the ischemic territory, peaking at two weeks post-stroke in human and one-week post-stroke in rat ischemic cortex. Using double immunofluorescence and mice lacking MANF gene and protein from neuronal stem cells, neurons, astrocytes, and oligodendrocytes, we verified that MANF expression was induced in microglia/macrophage cells in the ischemic hemisphere. Embarking on the drastic expression transition towards inflammatory cells and the impact of blood-borne inflammation in stroke, we hypothesized that exogenously delivered MANF protein can modulate tissue recovery processes. In an attempt to enhance recovery, we designed a set of proof-of-concept studies using systemic delivery of recombinant MANF in a rat model of cortical ischemic stroke. Intranasal recombinant MANF treatment decreased infarct volume and reduced the severity of neurological deficits. Intravenous recombinant MANF treatment decreased the levels of pro-inflammatory cytokines and increased the levels of anti-inflammatory cytokine IL-10 in the infarcted cortex one-day post-stroke. In conclusion, MANF protein expression is induced in activated microglia/macrophage cells in infarcted human and rodent brains, and this could implicate MANF's involvement in the regulation of post-stroke inflammation in patients and experimental animals. Moreover, systemic delivery of recombinant MANF shows promising immunomodulatory effects and therapeutic potential in experimental ischemic stroke.

Human milk-derived MANF, as an immuno-nutritional factor, maintains the intestinal epithelial barrier and protects against necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of death in preterm infants. Compared to formula milk, breastfeeding protects against NEC. However, the composition of breast milk is quite complicated, and many immunological compositions remain unknown. In this study, we aimed to investigate the concentration of a secreted protein, Mesencephalic astrocyte-derived neurotrophic factor (MANF), in breastmilk and evaluate its immune-regulatory function in protecting the intestinal epithelial barrier. Our data indicated that MANF was secreted in human milk but could not be detected in infant formulas. More importantly, the amount of MANF in colostrum was higher than that in mature milk. We also clarified that MANF was mainly expressed in intestinal macrophages and was capable of inducing apoptosis and decreasing the inflammation of pro-inflammatory macrophages in both NEC intestinal tissues and BMDMs. Mechanismly, MANF protein significantly inhibited the apoptosis of intestinal epithelial cells and protected epithelial tight junctions through downregulation of the NF-κB pathway in pro-inflammatory macrophages. These results reveal the crucial function of human milk-derived MANF in intestinal macrophages, which contributes to downregulating the intestinal inflammatory response and protecting the homeostasis of intestinal epithelial cells. Our study not only demonstrates a potential mechanism underlying breastfeeding protective effects in NEC but also, more importantly, enables clinical translation, facilitating new strategies for the development of nutritional interventions in the prevention of NEC.

Navigating the Landscape of MANF Research: A Scientometric Journey with CiteSpace Analysis

This study employs bibliometric analysis through CiteSpace to comprehensively evaluate the status and trends of MANF (mesencephalic astrocyte-derived neurotrophic factor) research spanning 25 years (1997-2022). It aims to fill the gap in objective and comprehensive reviews of MANF research. MANF-related studies were extracted from the Web of Science database. MANF publications were quantitatively and qualitatively analyzed for various factors by CiteSpace, including publication volume, journals, countries/regions, institutions, and authors. Keywords and references were visually analyzed to unveil research evolution and hotspot. Analysis of 353 MANF-related articles revealed escalating annual publications, indicating growing recognition of MANF's importance. High-impact journals such as the International Journal of Molecular Sciences and Journal of Biological Chemistry underscored MANF's interdisciplinary significance. Collaborative networks highlighted China and the USA's pivotal roles, while influential figures and partnerships drove understanding of MANF's mechanisms. Co-word analysis of MANF-related keywords exposed key evolutionary hotspots, encompassing neurotrophic effects, cytoprotective roles, MANF-related diseases, and the CDNF/MANF family. This progression from basic understanding to clinical potential showcased MANF's versatility from cellular protection to therapy. Bibliometric analysis reveals MANF's diverse research trends and pathways, from basics to clinical applications, driving medical progress. This comprehensive assessment enriches understanding and empowers researchers for dynamic evolution, advancing innovation, and benefiting patients. Bibliometric analysis of MANF research. The graphical abstract depicts the bibliometric analysis of MANF research, highlighting its aims, methods, and key results.

MANF brakes TLR4 signaling by competitively binding S100A8 with S100A9 to regulate macrophage phenotypes in hepatic fibrosis

The mesencephalic astrocyte-derived neurotrophic factor (MANF) has been recently identified as a neurotrophic factor, but its role in hepatic fibrosis is unknown. Here, we found that MANF was upregulated in the fibrotic liver tissues of the patients with chronic liver diseases and of mice treated with CCl4. MANF deficiency in either hepatocytes or hepatic mono-macrophages, particularly in hepatic mono-macrophages, clearly exacerbated hepatic fibrosis. Myeloid-specific MANF knockout increased the population of hepatic Ly6Chigh macrophages and promoted HSCs activation. Furthermore, MANF-sufficient macrophages (from WT mice) transfusion ameliorated CCl4-induced hepatic fibrosis in myeloid cells-specific MANF knockout (MKO) mice. Mechanistically, MANF interacted with S100A8 to competitively block S100A8/A9 heterodimer formation and inhibited S100A8/A9-mediated TLR4-NF-κB signal activation. Pharmacologically, systemic administration of recombinant human MANF significantly alleviated CCl4-induced hepatic fibrosis in both WT and hepatocytes-specific MANF knockout (HKO) mice. This study reveals a mechanism by which MANF targets S100A8/A9-TLR4 as a "brake" on the upstream of NF-κB pathway, which exerts an impact on macrophage differentiation and shed light on hepatic fibrosis treatment.

Prognostic potential of serum mesencephalic astrocyte-derived neurotrophic factor in acute intracerebral hemorrhage: a prospective observational study

OBJECTIVE

Mesencephalic astrocyte-derived neurotrophic factor (MANF) expressions are dramatically up-regulated in injured brain tissues, thereby conferring neurological protective effects. We intended to determine significance of serum MANF as a prognostic biomarker of intracerebral hemorrhage (ICH).

METHODS

In this prospective, observational study done from February 2018 to July 2021, 124 patients with new-onset primary supratentorial ICH were consecutively enrolled. Also, a group of 124 healthy individuals constituted controls. Their serum MANF levels were detected using the Enzyme-Linked Immunosorbent Assay. National Institutes of Health Stroke Scale (NIHSS) and hematoma volume were designated as the two severity indicators. Early neurologic deterioration (END) was referred to as an increase of 4 or greater points in NIHSS scores or death at post-stroke 24 h. Post-stroke 90-day modified Rankin scale (mRS) scores of 3-6 was considered as a poor prognosis. Serum MANF levels were analyzed using multivariate analysis with respect to its association with stroke severity and prognosis.

RESULTS

Patients, in comparison to controls, displayed markedly elevated serum MANF levels (median, 24.7 versus 2.7 ng/ml; P < 0.001), and serum MANF levels were independently correlated with NIHSS scores (beta, 3.912; 95% confidence interval (CI), 1.623-6.200; VIF = 2.394; t = 3.385; P = 0.002), hematoma volumes (beta, 1.688; 95% CI, 0.764-2.612; VIF = 2.661; t = 3.617; P = 0.001) and mRS scores (beta, 0.018; 95% CI, 0.013-0.023; VIF = 1.984; t = 2.047; P = 0.043). Serum MANF levels significantly predicted END and poor 90-day prognosis with areas under receiver operating characteristic curve at 0.752 and 0.787 respectively. END and prognostic predictive abilities were similar between serum MANF levels and NIHSS scores plus hematoma volumes (all P > 0.05). Combination of serum MANF levels with NIHSS scores and hematoma volumes had significantly higher prognostic capability than each of them (both P < 0.05). Serum MANF levels above 52.5 ng/ml and 62.0 ng/ml distinguished development of END and poor prognosis respectively with median-high sensitivity and specificity values. Using multivariate analysis, serum MANF levels > 52.5 ng/ml predicted END with odds ratio (OR) value of 2.713 (95% CI, 1.004-7.330; P = 0.042) and > 62.0 ng/ml predicted a poor prognosis with OR value of 3.848 (95% CI, 1.193-12.417; P = 0.024). Using restricted cubic spline, there was a linear correlation between serum MANF levels and poor prognosis or END risk (both P > 0.05). Nomograms were well established to predict END and a poor 90-day prognosis. Under calibration curve, such combination models were comparatively stable (using Hosmer & Lemeshow test, both P > 0.05).

CONCLUSION

Increased serum MANF levels after ICH, in independent correlation with disease severity, independently distinguished risks of END and 90-day poor prognosis. Therefore, serum MANF may be a potential prognostic biomarker of ICH.

A prospective observational study on utility of serum mesencephalic astrocyte-derived neurotrophic factor as a promising prognostic biomarker of severe traumatic brain injury in humans

BACKGROUND

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is released under endoplasmic reticulum stress, thereby exerting neuroprotective effects. We determined whether serum MANF may be a prognostic biomarker of human severe traumatic brain injury (sTBI).

METHODS

Serum MANF concentrations of 137 sTBI patients and 137 controls were quantified in this prospective cohort study. Patients with extended Glasgow outcome scale (GOSE) scores of 1-4 at post-traumatic 6 months were considered to have poor prognosis. Relationships between serum MANF concentrations and severity plus prognosis were investigated using multivariate analyses. Area under receiver operating characteristic curve (AUC) was calculated for reflecting prognostic efficiency.

RESULTS

As compared to controls, there was a significant increase of serum MANF concentrations after sTBI (median, 18.5 ng/ml versus 3.0 ng/ml; P<0.001), which was independently correlated with Glasgow coma scale (GCS) scores [β, -3.000; 95% confidence interval (CI), -4.525--1.476; VIF, 2.216; P=0.001], Rotterdam computed tomography (CT) scores (β, 4.020; 95% CI, 1.446-6.593; VIF, 2.234; P=0.002) and GOSE scores (β, -0.056; 95% CI, -0.089--0.023; VIF, 1.743; P=0.011). Serum MANF concentrations substantially distinguished risk of poor prognosis with AUC of 0.795 (95% CI, 0.718-0.859) and its concentrations >23.9 ng/ml was predictive of poor prognosis with 67.7% sensitivity and 81.9% specificity. Serum MANF concentrations combined with GCS scores and Rotterdam CT scores displayed markedly higher prognostic predictive ability than each of them (all P<0.05). Using restricted cubic spline, there was a linear correlation between serum MANF concentrations and poor prognosis (P=0.256). Serum MANF concentrations > 23.9 ng/ml was independently associated with poor prognosis (odds ratio, 2.911; 95% CI, 1.057-8.020; P=0.039). A nomogram was built, where serum MANF concentrations > 23.9 ng/ml, GCS scores and Rotterdam CT scores were integrated. Hosmer and Lemeshow test, calibration curve and decision curve analysis demonstrated such a prediction model was comparatively stable and was of relatively high clinical benefit.

CONCLUSIONS

Substantially increased serum MANF concentrations after sTBI are highly correlated with traumatic severity and are independently predictive of long-term poor prognosis, suggesting that serum MANF may represent a useful prognostic biochemical marker of human sTBI.

Effects of mesencephalic astrocyte-derived neurotrophic factor on sepsis-associated acute kidney injury

BACKGROUND

To determine the protective role of mesencephalic astrocyte-derived neurotrophic factor (MANF) in regulating sepsis-associated acute kidney injury (S-AKI).

METHODS

A total of 96 mice were randomly divided into the control group, control+MANF group, S-AKI group, and S-AKI+MANF group. The S-AKI model was established by injecting lipopolysaccharide (LPS) at 10 mg/kg intraperitoneally. MANF (200 μg/kg) was administered to the control+MANF and S-AKI+MANF groups. An equal dose of normal saline was administered daily intraperitoneally in the control and S-AKI groups. Serum and kidney tissue samples were obtained for biochemical analysis. Western blotting was used to detect the protein expression of MANF in the kidney, and enzyme-linked immunosorbent assay (ELISA) was used to determine expression of MANF in the serum, pro-inflammatory cytokines (tumor necrosis factor-α [TNF-α] and interleukin-6 [IL-6]). Serum creatinine (SCr), and blood urea nitrogen (BUN) were examined using an automatic biochemical analyzer. In addition, the kidney tissue was observed for pathological changes by hematoxylin-eosin staining. The comparison between two groups was performed by unpaired Student's t-test, and statistics among multiple groups were carried out using Tukey's post hoc test following one-way analysis of variance (ANOVA). A P-value <0.05 was considered statistically significant.

RESULTS

At the early stage of S-AKI, MANF in the kidney tissue was up-regulated, but with the development of the disease, it was down-regulated. Renal function was worsened in the S-AKI group, and TNF-α and IL-6 were elevated. The administration of MANF significantly alleviated the elevated levels of SCr and BUN and inhibited the expression of TNF-α and IL-6 in the kidney. The pathological changes were more extensive in the S-AKI group than in the S-AKI+MANF group.

CONCLUSION

MANF treatment may significantly alleviate renal injury, reduce the inflammatory response, and alleviate or reverse kidney tissue damage. MANF may have a protective effect on S-AKI, suggesting a potential treatment for S-AKI.

Increased serum concentrations of Mesencephalic astrocyte-derived neurotrophic factor in patients and rats with ischemic stroke

OBJECTIVES

Although Mesencephalic astrocyte-derived neurotrophic factor (MANF) shows protection in multiple cells, the role of circulating MANF in patients with acute ischemic stroke (AIS) and transient ischemic attack (TIA) remains unclear. Here, we aimed to explore the value of circulating MANF levels in cerebral ischemic events.

MATERIALS AND METHODS

Using a rat cerebral ischemic model, MANF expression in ischemic brains and serum was detected. 50 AIS patients, 56 TIA patients and 48 controls were enrolled, and MANF mRNA, inflammatory cytokines and MANF concentrations in serum and different blood cell types were detected. The National Institutes of Health Stroke Scale (NIHSS) score and Alberta Stroke Program Early CT Score (ASPECTS) were used to evaluate stroke severity. Cerebrovascular recurrence within 90 d was documented during TIA follow-up.

RESULTS

MANF expression increased at 2h, peaking at 24h and decreased to baseline at 7d in rat ischemic brains and serum. Serum MANF concentrations increased at 24h and 7d in AIS patients compared to controls and were correlated with NIHSS score, ASPECTS and inflammatory cytokines. MANF protein was present in blood cells, while MANF mRNA levels did not differ between AIS patients and controls. MANF levels revealed a good value to diagnose TIA with area under the curve (AUC) of 0.949 (95% CI: 0.9093-0.9892). MANF levels were lower in TIA patients with recurrence compared to non-recurrence patients. The AUC for MANF to predict a re-event was 0.80 (95% CI: 0.6746-0.9282).

CONCLUSIONS

Serum MANF levels correlate with neuroprotection, stroke severity, inflammation, and TIA recurrence.

Mesencephalic astrocyte-derived neurotrophic factor attenuates acute lung injury via inhibiting macrophages' activation

Acute lung injury (ALI) is an urgent respiratory disease without effective treatment. Mesencephalic astrocyte-derived neurotrophic factor (MANF)has been demonstrated to play a suppressive role in some inflammatory conditions. However, the effect of MANF on ALI has not yet been reported. In this study, we collected bronchoalveolar lavage fluid (BALF) from the patients with or without pulmonary inflammation, and used lipopolysaccharide (LPS) to induce mice ALI model. Mono-macrophage-specific MANF knockout (MKO) mice were constructed and recombinant human MANF protein was used to ALI mice. We found that the endogenous MANF protein in both human BALF and mice lung tissues was increased in inflammatory conditions. MANF level in the macrophages of inflammatory lung was higher than that in normal controls in both human and mice. MANF deficiency in macrophages induced lung inflammation and aggravated LPS-induced lung injury. MANF lowered LPS-induced lung injury, inhibited macrophage polarization to M1 functional type. Meanwhile, MANF inhibited-LPS induced activation of NF-κB signal pathway by down regulating phosphorylated p65in lung tissue and macrophages. These results indicate that MANF acts as a suppressor in ALI via negatively regulating NF-κB activation and macrophages polarization, which may be a novel potential target and shed light on ALI therapy.

Mesencephalic astrocyte-derived neurotrophic factor restores blood-brain barrier integrity of aged mice after ischaemic stroke/reperfusion through anti-inflammation via TLR4/MyD88/NF-κB pathway

Ischaemic stroke remains a leading cause of disability and mortality worldwide and ageing-associated inflammation for the aged patients specifically leads to worse post-stroke blood-brain barrier (BBB) disruption than young subjects. Accordingly, suppression of excessive inflammation can alleviate BBB injury, which provides potential therapeutic treatment for ischaemic stroke of the aged. Prior studies revealed that mesencephalic astrocyte-derived neurotrophic factor (MANF) regulated inflammatory response and alleviated liver injury in ageing. However, it is unclear whether MANF confer similar benefit to BBB of aged mice suffered from ischaemic stroke. Transient cerebral ischaemia induced by middle cerebral artery occlusion (MCAO) was conducted in aged mice (18-20 months old). MANF was injected into the right lateral ventricle 2 h after MCAO. BBB integrity, tight junctional proteins, ultrastructure of microvessels, infarct volume, neurological scores, brain water content, pro-inflammatory cytokines and neutrophil infiltration rate were determined 72 h after MCAO. H₂O₂-induced senescent bEnd.3 cells were applied in the in vitro study to investigate the possible mechanism. First, we confirmed that ischaemic stroke/reperfusion in senescent condition promoted the over-expression of MANF on brain endothelial cells. Then, MANF supplement could suppress the pro-inflammatory factor production, restore BBB integrity and then alleviate infarct volume, neurological scores, brain water content and neutrophil infiltration rate. In addition, MANF maintained BBB integrity after ischaemic stroke of aged condition dependent on TLR4/MyD88/NF-κB pathway via intervention of pro-inflammatory factors production. In summary, the recognition of MANF in the process of BBB breakdown at aged condition may offer novel therapeutic approaches for ischaemic stroke.

Mono-macrophage-Derived MANF Alleviates Bacterial Myocarditis by Inhibiting NF-kappaB Activation and Myocardial Inflammation

Bacterial myocarditis is a key cause leading to myocardial damage and cardiac dysfunction. Mesencephalic astrocyte-derived neurotrophic factor (MANF) has been found to be an anti-inflammatory factor. This study is to explore the effect of MANF on LPS-induced myocardial inflammation and macrophage differentiation. The myocarditis mouse model was constructed by LPS treatment. Myocardial damage and serum inflammatory factors were evaluated by ELISA. RT-qPCR was used to detect mRNA of M1/M2 macrophage markers. Western blot, immunohistochemical, and immunofluorescent staining were used to examine myocardial M1/M2 macrophages and NF-κB activation. Mono-macrophage-derived MANF deficiency enhanced LPS-induced inflammatory response and increased M1 macrophages in myocardium tissues, further causing more severe myocardial injury and lower survival rate of mice. Also, LPS-induced myocardial NF-κB activation was strengthened after mono-macrophage-derived MANF knockout. Mono-macrophage-derived MANF inhibits bacterial myocarditis and myocardial M1 macrophage differentiation, which is potential to be used for bacterial myocarditis treatment clinically.

Mesencephalic astrocyte-derived neurotrophic factor ameliorates steatosis in HepG2 cells by regulating hepatic lipid metabolism

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a global metabolism-associated liver disease. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered secreted protein that is involved in metabolic homeostasis. However, much remains to be discovered about its function in hepatic lipid metabolism; thus, we assessed whether MANF could regulate hepatic metabolism.

AIM

To establish in vivo and in vitro NAFLD models to explore the role of MANF in hepatic lipid metabolism.

METHODS

HepG2 cells treated with free fatty acids (FFAs) and ob/ob mice were used as NAFLD models. Liver tissues collected from wild type and ob/ob mice were used to detect MANF expression. Cells were treated with FFAs for different durations. Moreover, we used lentiviral constructs to establish overexpression and knockdown cell models in order to interfere with MANF expression levels and observe whether MANF influences hepatic steatosis. Western blot analysis and quantitative real-time PCR were used to detect protein and gene expression, and oil red O staining was used to visualize intracellular lipid droplets.

RESULTS

Hepatic MANF protein and mRNA expression in wild type mice were 10-fold and 2-fold higher, respectively, than those in ob/ob mice. The MANF protein was temporarily increased by 1.3-fold after stimulation with FFAs for 24 h and gradually decreased to 0.66-fold that of the control at the 72 h time point in HepG2 cells. MANF deficiency upregulated the expression of genes involved in fatty acid synthesis, cholesterol synthesis, and fatty acid uptake and aggravated HepG2 cell steatosis, while MANF overexpression inhibited fatty acid synthesis and uptake and cholesterol synthesis, and rescued HepG2 cells from FFAs-induced steatosis. Furthermore, a significant decrease in triglyceride levels was observed in the MANF overexpression group compared with the control group (0.4288 ± 0.0081 mmol/g vs 0.3746 ± 0.0121 mmol/g, P < 0.05) upon FFAs treatment. There was also a 17% decrease in intracellular total cholesterol levels between the MANF overexpression group and the control group (0.1301 ± 0.0059 mmol/g vs 0.1088 ± 0.0009 mmol/g, P < 0.05) upon FFAs treatment. Moreover, MANF suppressed lipid deposition in HepG2 cells.

CONCLUSION

Our findings indicate that MANF improves the phenotype of liver cell steatosis and may be a potential therapeutic target in hepatic steatosis processes.

Effects of mesencephalic astrocyte-derived neurotrophic factor on cerebral angiogenesis in a rat model of cerebral ischemia

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum stress-related protein that exhibits neuroprotective effects. Recent studies have shown that MANF promotes poststroke functional recovery in rats. However, the underlying mechanisms have not yet been fully understood. Here, we examined the effects of MANF on cerebral angiogenesis in a permanent middle cerebral artery occlusion model in rats. Recombinant human MANF was administered intracerebroventricularly 24 h after stroke. We performed neurobehavioral tests and assessed microvessel density, functional microvessels, and regional cerebral blood flow (rCBF), as well as detected angiogenic factors in the peri-infarct cerebral cortex. Results showed that MANF ameliorated neurobehavioral scores, promoted rCBF, upregulated the expression of CD34, as well as the total vessel surface area and the number of microvessel branch points, and activated the vascular endothelial growth factor (VEGF) pathway. In conclusion, our findings provide insight into the mechanisms of MANF in promoting functional recovery from ischemic stroke. Our results suggest that MANF improves neurobehavioral recovery from cerebral ischemic injury, and that this effect is mediated partly by its proangiogenic effects and augmentation of rCBF, which are possibly associated with VEGF.

MANF regulates splenic macrophage differentiation in mice. Immunol Lett. 2019;212:37-45. [PMID: 31226359 DOI: 10.1016/j.imlet.2019.06.007]

Splenic immune cells, especially macrophages, play a key role in multiple pathological processes. With a proved anti-inflammatory and immunoregulatory function of mesencephalicastrocyte-derived neurotrophic factor (MANF) in inflammatory disorders, how MANF affects splenic immune cells in physiological and pathophysiological situations is still unknown. In this study, we constructed mono-macrophage-specific MANF knockout (Mø MANF^-/-) mice and found the increased splenic M1 macrophages, but no significant change of splenic morphology and size compared with wild type (WT) mice. Also, we established the pathophysiological situation of carbon tetrachloride (CCl₄)-induced hepatic fibrosis. Under the hepatic fibrosis, splenic M2 macrophages and CD138⁺ plasma cells were significantly increased in Mø MANF^-/- mice. Consistently, we found the increased TGF-β1 level in serum and spleen of Mø MANF^-/- mice as well. Mono-macrophage-specific MANF knockout did not affect the number of splenic T and B cells under both the normal and hepatic fibrosis conditions. Our results suggest a distinct regulation of MANF on splenic immune cells and a specific regulation of MANF on the differentiation of splenic macrophages, which may exert a significant impact on physiological and pathophysiological processes of the spleen.

XBP1 activation enhances MANF expression via binding to endoplasmic reticulum stress response elements within MANF promoter region in hepatitis B

As an endoplasmic reticulum (ER) stress-related protein, mesencephalic astrocyte-derived neurotrophic factor (MANF) is involved in inflammatory diseases, such as rheumatoid arthritis. However, the mechanisms of the transcriptional regulation of MANF is still undefined. Here, we showed that MANF expression was upregulated in hepatitis B tissues and hepatoma cells, and positively correlated with the spliced X-box binding protein-1 (XBP1s). Both overexpression of XBP1s and tunicamycin treatment were able to enhance MANF transcription. On the contrary, inhibition of XBP1 splicing by IRE1α endonuclease inhibitor or knockdown of XBP1s with siRNA attenuated MANF expression. Two ER stress-responsive elements (ERSE) were found in the promoter region of MANF (ERSE I and ERSE II). The chromatin immunoprecipitation and reporter gene assay showed that XBP1s mainly binds to ERSE I to promote MANF transcription. Moreover, MANF was found to interact with XBP1s to enhance its own expression. Our findings uncover a new mechanism of ERSE-dependent transcriptional regulation of MANF, as well as a key role of XBP1s in promoting the MANF expression.

Circulating mesencephalic astrocyte-derived neurotrophic factor is increased in newly diagnosed prediabetic and diabetic patients, and is associated with insulin resistance

Evidence has shown that endoplasmic reticulum (ER) stress was involved in the progression to type 2 diabetes mellitus (T2DM) and development of insulin resistance. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a novel secreted protein upregulated by ER stress. This study aimed to assess serum level of MANF in normal glucose tolerance (NGT) participants and newly diagnosed prediabetic and T2DM patients. A total of 257 participants with NGT, newly diagnosed prediabetes or T2DM were recruited from Yinchao and Hangtian communities of Chengdu, Sichuan, China. Serum MANF level was quantified by enzyme-linked immunosorbent assay (ELISA). The mean age for the 257 participants (147 females) was 62±8 years (range 44-78): 71 with NGT, 115 with newly diagnosed prediabetes and 71 with T2DM. Mean serum MANF level was significantly higher with newly diagnosed prediabetes and T2DM than NGT (2.89±1.09 and 3.03±1.73 vs 2.13±1.37 ng/mL, both p<0.001). MANF level was not correlated with insulin sensitivity indexes (homeostasis model assessment for insulin resistance [HOMA-IR], Matsuda Index and quantitative insulin sensitivity check index [QUICKI]) for NGT and T2DM participants but was correlated with such indexes for prediabetes patients. We concluded that serum MANF level was higher in patients with newly diagnosed prediabetes and T2DM than in NGT controls. MANF appears to be associated with Matsuda Index, QUICKI and HOMA-IR in prediabetes patients.

Long-term protective effects of AAV9-mesencephalic astrocyte-derived neurotrophic factor gene transfer in parkinsonian rats

Intrastriatal injection of mesencephalic astrocyte-derived neurotrophic factor (MANF) protein has been shown to provide neuroprotective and neurorestorative effects in a 6-hydroxydopamine (6-OHDA) - lesioned rat model of Parkinson's disease. Here, we used an adeno-associated virus serotype 9 (AAV9) vector to deliver the human MANF (hMANF) gene into the rat striatum 10days after a 6-OHDA lesion to examine long-term effects of hMANF on nigral dopaminergic neurons and mechanisms underlying MANF neuroprotection. Intrastriatal injection of AAV9-hMANF vectors led to a robust and widespread expression of the hMANF gene in the injected striatum up to 24weeks. Increased levels of hMANF protein were also detected in the ipsilateral substantia nigra. The hMANF gene transfer promoted the survival of nigral dopaminergic neurons, regeneration of striatal dopaminergic fibers and an upregulation of striatal dopamine levels, resulting in a long-term improvement of rotational behavior up to 16weeks after viral injections. By using SH-SY5Y cells, we found that intra- and extracellular application of MANF protected cells against 6-OHDA-induced toxicity via inhibiting the endoplasmic reticulum stress and activating the PI3K/Akt/mTOR pathway. Our results suggest that AAV9-mediated hMANF gene delivery into the striatum exerts long-term neuroprotective and neuroregenerative effects on the nigrostriatal dopaminergic system in parkinsonian rats, and provide insights into mechanisms responsible for MANF neuroprotection.

Therapeutic potential of the endoplasmic reticulum located and secreted CDNF/MANF family of neurotrophic factors in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder where dopamine (DA) neurons in the substantia nigra degenerate and die. Since no cure for PD exists, there is a need for disease-modifying drugs. Glial cell line-derived neurotrophic factor (GDNF) and related neurturin (NRTN) can protect and repair DA neurons in neurotoxin animal models of PD. However, GDNF was unable to rescue DA neurons in an α-synuclein model of PD, and both factors have shown modest effects in phase two clinical trials. Neurotrophic factors (NTFs), cerebral DA NTF (CDNF) and mesencephalic astrocyte-derived NTF (MANF) form a novel family of evolutionarily conserved, endoplasmic reticulum (ER) located and secreted NTFs. CDNF and MANF have a unique structure and an unparalleled dual mode of action that differs from other known NTFs. Both protect cells from ER stress, and regulate the unfolded protein response via interacting with chaperons, and CDNF dissolves intracellular α-synuclein aggregates. By binding to putative plasma membrane receptors, they promote the survival of DA neurons similarly to conventional NTFs. In animal models of PD, CDNF protects and repairs DA neurons, regulates ER stress, and improves motor function more efficiently than other NTFs.

Mesencephalic astrocyte-derived neurotrophic factor prevents neuron loss via inhibiting ischemia-induced apoptosis

Mesencephalic astrocyte-derived neurotrophic factor (MANF) has been shown to be up-regulated under the focal cerebral ischemia and protected against ischemic injury in rats. However, the underlying mechanisms are unclear. The aim of this study was to verify the protection of MANF on the cerebral ischemic injury and further investigate the possible mechanisms. Rat focal ischemic model was established by middle cerebral artery occlusion (MCAO). The recombinant human MANF was therapeutically administrated to the ipsilateral ventricle at 2 h after MCAO. MANF decreased the number of the propidium iodide (PI)- and TUNEL-positive neural cells. Contrarily, MANF protected the NeuN-positive cells in hippocampus and cortex from death induced by ischemia. The more interesting results in this study were that MANF repressed the cleavage of caspase-3 triggered by focal cerebral ischemia. MANF also reduced the elevated levels of BIP/Grp78, phosphorylated IRE1, and splicing XBP1 induced by focal cerebral ischemia, but not affect CHOP expression. Meanwhile, focal cerebral ischemia elevated the levels of XBP1 mRNA, including unspliced XBP1 (XBP1u) and spliced XBP1 (XBP1s). However, MANF did not affect the expression of XBP1 mRNA, neither XBP1u nor XBP1s. These results suggest that MANF can prevent the neuron loss via inhibiting ischemia-induced apoptosis and regulating unfolded protein response-related genes.