Desferoxamine preconditioning protects against cerebral ischemia in rats by inducing expressions of hypoxia inducible factor 1α and erythropoietin

Objective To investigate whether desferoxamine （DFO） preconditioning can induce tolerance against cerebral ischemia and its effect on the expression of hypoxia inducible factor 1 α （HIF- 1α） and erythropoietin （EPO） in vivo and in vitro. Methods Rat model of cerebral ischemia was established by middle cerebral artery occlusion with or without DFO administration. Infarct size was examined by TTC staining, and the neurological severity score was evaluated according to published method. Cortical neurons were cultured under ischemia stress which was mimicked by oxygen-glucose deprivation （OGD）, and the neuron damage was assessed by MTT assay. Immunofluorescent staining was employed to detect the expressions of HIF-1 and EPO. Results The protective effect induced by DFO （decreasing the infarction volume and ameliorating the neurological function） appeared at 2 d after administration ofDFO （post-DFO）, lasted until 7 d and disappeared at 14 d （P 〈 0.05）; the most effective action was observed at 3 d post-DFO. DFO induced tolerance of cultured neurons against OGD： neuronal viability was increased 23%, 34%, 40%, 48% and 56% at 8 h, 12 h, 24 h, 36 h, and 48 h, respectively, post-DFO （P 〈 0.05）. Immunofluorescent staining found that HIF-1 α and EPO were upregulated in the neurons of rat brain at 3 d and 7 d post-DFO; increase of HIF-1 α and EPO appeared in cultured cortex neurons at 36 h and 48 h post-DFO. Conclusion DFO induced tolerance against focal cerebral ischemia in rats, and exerted protective effect on OGD cultured cortical neurons. DFO significant induced the expression of HIF- 1 α and EPO both in vivo and in vitro. DFO preconditioning can protect against cerebral ischemia, which may be associated with the synthesis of HIF- 1 α and EPO.

DI-3-n-butylphthalide exerts neuroprotective effects by modulating hypoxia-inducible factor 1-alpha ubiquitination to attenuate oxidative stress-induced apoptosis

DI-3-n-butylphthalide is used to treat mild and moderate acute ischemic stroke.However,the precise underlying mechanism requires further investigation.In this study,we investigated the molecular mechanism of DI-3-n-butylphthalide action by various means.We used hydrogen peroxide to induce injury to PC12cells and RAW264.7 cells to mimic neuronal oxidative stress injury in stroke in vitro and examined the effects of DI-3-n-butylphthalide.We found that DI-3-nbutylphthalide pretreatment markedly inhibited the reduction in viability and reactive oxygen species production in PC12 cells caused by hydrogen peroxide and inhibited cell apoptosis.Furthermore,DI-3-n-butylphthalide pretreatment inhibited the expression of the pro-apoptotic genes Bax and Bnip3.DI-3-nbutylphthalide also promoted ubiquitination and degradation of hypoxia inducible factor 1α,the key transcription factor that regulates Bax and Bnip3 genes.These findings suggest that DI-3-n-butylphthalide exhibits a neuroprotective effect on stroke by promoting hypoxia inducible factor-1α ubiquitination and degradation and inhibiting cell apoptosis.

Expression of caspase-3 and hypoxia inducible factor 1αin hepatocellular carcinoma complicated by hemorrhage and necrosis

BACKGROUND Hepatocellular carcinoma(HCC)is a malignant tumor that occurs in the liver.Its onset is latent,and it shows high heterogeneity and can readily experience intrahepatic metastasis or systemic metastasis,which seriously affects patients’quality of life.Numerous studies have shown that hypoxia inducible factor1α(HIF-1α)plays a significant role in the occurrence and development of tumors,as it promotes the formation of intratumoral vessels and plays a key role in their metastasis and invasion.Some studies have reported that caspase-3,which is induced by various factors,is involved in the apoptosis of tumor cells.AIM To investigate the expression of caspase-3 and HIF-1αand their relationship to the prognosis of patients with primary HCC complicated by pathological changes of hemorrhage and necrosis.METHODS A total of 88 patients with HCC complicated by pathological changes of hemorrhage and necrosis who were treated at our hospital from January 2017 to December 2019 were selected.The expression of caspase-3 and HIF-1αin HCC and paracancerous tissues from these patients was assessed.RESULTS The positive expression rate of caspase-3 in HCC tissues was 27.27%,which was significantly lower than that in the paracancerous tissues(P<0.05),while the positive expression rate of HIF-1αwas 72.73%,which was significantly higher than that in the paracancerous tissues(P<0.05).The positive expression rates for caspase-3 in tumor node metastasis(TNM)stage III and lymph node metastasis tissues were 2.78%and 2.50%,respectively,which were significantly lower than those in TNM stage I-II and non-lymph node metastasis tissues(P<0.05).The positive expression rates of HIF-1αin TNM stage III,lymph node metastasis,and portal vein tumor thrombus tissues were 86.11%,87.50%,and 88.00%,respectively,and these values were significantly higher than those in TNM stage I-II,non-lymph node metastasis,and portal vein tumor thrombus tissues(P<0.05).The expression of caspase-3 and HIF-1αin HCC tissues were negatively correlated(rs=−0.426,P<0.05).The median overall survival time of HCC patients was 18.90 mo(95%CI:17.20–19.91).The results of the Cox proportional risk regression model analysis showed that TNM stage,portal vein tumor thrombus,lymph node metastasis,caspase-3 expression,and HIF-1αexpression were the factors influencing patient prognosis(P<0.05).CONCLUSION The expression of caspase-3 decreases and HIF-1αincreases in HCC tissues complicated by pathological changes of hemorrhage and necrosis,and these are related to clinicopathological features and prognosis.

Sirtuin1 attenuates acute liver failure by reducing reactive oxygen species via hypoxia inducible factor 1α

BACKGROUND The occurrence and development of acute liver failure(ALF)is closely related to a series of inflammatory reactions,such as the production of reactive oxygen species(ROS).Hypoxia inducible factor 1α(HIF-1α)is a key factor that regulates oxygen homeostasis and redox,and the stability of HIF-1αis related to the ROS level regulated by Sirtuin(Sirt)family.The activation of Sirt1 will lead to a powerful antioxidant defense system and therapeutic effects in liver disease.However,little is known about the relationship between HIF-1αand Sirt1 in the process of ALF and the molecular mechanism.AIM To investigate whether HIF-1αmay be a target of Sirt1 deacetylation and what the effects on ALF are.METHODS Mice were administrated lipopolysaccharide(LPS)/D-gal and exposed to hypoxic conditions as animal model,and resveratrol was used as an activator of Sirt1.The cellular model was established with L02 cells stimulated by LPS.N-acetyl-Lcysteine was used to remove ROS,and the expression of Sirt1 was inhibited by nicotinamide.Western blotting was used to detect Sirt1 and HIF-1αactivity and related protein expression.The possible signaling pathways involved were analyzed by immunofluorescent staining,co-immunoprecipitation,dihydroethidium staining,and Western blotting.RESULTS Compared with mice stimulated with LPS alone,the expression of Sirt1 decreased,the level of HIF-1αacetylation increased in hypoxic mice,and the levels of carbonic anhydrase 9 and Bcl-2-adenovirus E1B interacting protein 3 increased significantly,which was regulated by HIF-1α,indicating an increase of HIF-1αactivity.Under hypoxia,the down-regulation of Sirt1 activated and acetylated HIF-1αin L02 cells.The inhibition of Sirt1 significantly aggravated this effect and the massive production of ROS.The regulation of ROS was partly through peroxisome proliferatoractivated receptor alpha or AMP-activated protein kinase.Resveratrol,a Sirt1 activator,effectively relieved ALF aggravated by hypoxia,the production of ROS,and cell apoptosis.It also induced the deacetylation of HIF-1αand inhibited the activity of HIF-1α.CONCLUSION Sirt1 may have a protective effect on ALF by inducing HIF-1α deacetylation to reduce ROS.

Hypoxia inducible factor 1α promotes interleukin-1 receptor antagonist expression during hepatic ischemia-reperfusion injury

BACKGROUND Ischemia-reperfusion injury(IRI) is a major risk associated with liver surgery and transplantation,and its pathological mechanism is complex.Interleukin-1 receptor antagonist(IL-1ra) can protect the liver from IRI.However,the regulatory mechanism of IL-1ra expression is still unclear.AIM To identify the mechanism that could protect the liver in the early stage of IRI.METHODS To screen the key genes in hepatic IRI,we performed RNA sequencing and gene enrichment analysis on liver tissue from mice with hepatic IRI.Subsequently,we verified the expression and effect of IL-1ra in hepatic IRI.We also used promoter mutagenesis and chromatin immunoprecipitation assay to search for the transcriptional regulatory sites of hypoxia-inducible factor(HIF)-1α.Finally,to explore the protective mechanism of ischemic preconditioning(IP),we examined the expression of HIF-1α and IL-1ra after IP.RESULTS We identified IL-1ra as a key regulator in hepatic IRI.The expression of IL-1ra was significantly upregulated after hepatic IRI both in vivo and in vitro.Furthermore,we found that HIF-1αregulated Il-1ra transcription in response to hypoxia.Increased HIF-1α accumulation promoted IL-1ra expression,whereas inhibition of HIF-1α exhibited the opposite effect.We also confirmed a predominant role for hypoxia response element in the regulation of Il1ra transcription by HIF-1αactivation.Of note,we demonstrated that IP protects against hepatic IRI by inducing IL-1ra expression,which is mediated through HIF-1α.CONCLUSION We demonstrated that ischemia or hypoxia leads to increased expression of IL-1ra through HIF-1α.Importantly,IP protects the liver from IRI via the HIF-1α–IL-1ra pathway.

Hypoxia-inducible factor 1 alpha upregulates the expression of inducible nitric oxide synthase gene in pulmonary arteries of hypoxic rat

Objective To investigate the expression of hypoxia inducible factor 1 alpha (HIF 1α) and inducible nitric oxide synthase (iNOS) genes in rats’ pulmonary arteries in different phases of hypoxia induced pulmonary hypertension development Methods Models of chronic hypoxic pulmonary hypertension rat were duplicated by intermittent hypoxia Mean pulmonary arterial pressure (mPAP) was measured by right heart catheterization HIF 1α and iNOS messenger ribonucleic acid (mRNA) were detected by in situ hybridization HIF 1α and iNOS protein were measured by immunohistochemical analysis Results Expression of HIF 1α protein was upregulated in pulmonary arterial tunica intimae of all hypoxic rats In pulmonary arterial tunica media, the level of HIF 1α protein was markedly upregulated at days 3 and 7 of hypoxia ( P 【0 01), then tended to restore at 14 days and 21 days HIF 1α mRNA levels in pulmonary arteries of rats began to increase significantly at day 14 of hypoxia ( P 【0 01) Expression of iNOS mRNA and protein in pulmonary arteries of rats were upregulated by hypoxia for 3 days ( P 【0 01), then reached its peak and maitained the same level while the extension of hypoxia Linear correlation analysis showed that iNOS protein was associated with both mean pulmonary arterial pressure ( r =0 74, P 【0 01) and hypoxic pulmonary vascular remodeling ( r =0 78, P 【0 01), whereas the inverse was associated with HIF 1α protein ( r =-0 52, P 【0 01) Conclusions HIF 1α and iNOS are both involved in the pathogenesis of hypoxia induced pulmonary hypertension in rat HIF 1α protein may upregulate the expression of iNOS gene by transcriptional activation; in addition, iNOS protein may inhibit the expression of HIF 1α protein

Chronic intermittent hypoxia increases β cell mass and activates the mammalian target of rapamycin/hypoxia inducible factor 1/vascular endothelial growth factor A pathway in mice pancreatic islet

Background Growing evidence from population and clinic based studies showed that obstructive sleep apnea （OSA） and its characterizing chronic intermittent hypoxia （IH） were independently associated with the development of type 2 diabetes mellitus.However,the pathogenesis by which OSA induces glucose metabolic disorders is not clear.We determined changes in pancreatic β cell mass and the mammalian target of rapamycin （mTOR）/hypoxia inducible factor 1 （HIF-1）/ vascular endothelial growth factor A （VEGF-A） pathway following IH exposure.Methods A controlled gas delivery system regulated the flow of nitrogen and oxygen into a customized cage housing mice during the experiment.Twenty-four male wild C57BL/6J mice were either exposed to IH （n=12） or intermittent air as a control （n=12） for 56 days.Mice were anaesthetized and sacrificed after exposure,pancreas samples were dissected for immunofluorescent staining.Insulin and DAPI staining labelled islet β cells.Insulin positive area and β cell number per islet were measured.P-S6,HIF-1α and VEGF-A staining were performed to detect the activation of mTOR/HIF-1NEGF-A pathway.Results After eight weeks of IH exposure,insulin positive area increased by an average of 18.5% （P 〈0.05）.The β cell number per islet increased （92 vs.55,respectively for IH and the control groups,P 〈0.05） with no change in the size of individual β cells.Islet expression of HIF-1α and VEGF-A were higher in IH group than control group,and percentage of p-S6 positive β cell also increased after IH exposure （16.8% vs.4.6% respectively for IH and the control groups,P 〈0.05）.Conclusion The number of pancreatic β cells increased as did the activity of the mTOR/HIF-1NEGF-A pathway after exposure to IH.

The expression of HIF-1α and VEGF as well as their correlation with angiogenesis in esophageal squamous cell carcinomas

Objective： To investigate the correlations among the expressions of hypoxia-inducible factor-1α （HIF-1α）, vascular endothelial cell growth factor （VEGF） and microvessel density （MVD）, and their relationships to the clinicopathologic characteristics of esophageal squamous cell carcinomas （ESCC）. Methods： The expressions of HIF-1α, VEGF and MVD were detected by immunohistochemical method in 45 cases of ESCC, 30 intraepithelial neoplasia and 35 normal esophageal mucosal epithelia tissues. The correlations among the expressions of HIF-1α, VEGF and MVD, and their relationships to the clinicopathologic features of ESCC were analyzed. Results： The rate of positive expression of HIF-1α and VEGF which were 80% and 84% in ESCC were significantly higher than those in intraepithelial neoplasia and normal esophageal mucosal epithelium tissues （P 〈 0.01） and so did the MVD value which was71.10 ±15.02 in ESCC （P 〈 0.01）. The expression of HIF-1α and VEGF were positively correlated with the depth of tumor invasion, lymph node metastasis and TNM staging of ESCC. The expressions of HIF-1α were positively correlated with the expressions of VEGF and the value of MVD. Conclusion： Overexpression of HIF-1α is found in ESCC. HIF-1α may induce the angiogenesis in ESCC by upregulating the transcription of VEGF gene. It may play an important role in the carcinogenesis and aggression in ESCC, HIF-1α, VEGF and MVD may be a useful marker for evaluating the biological behaviors of ESCC.

Anti-arthritis effect of berberine associated with regulating energy metabolism of macrophage through AMPK/HIF-1α pathway

OBJECTIVE To investigate berberine(BBR)attenuates arthritis in adjuvant-induced arthritic(AA)rats associated with regulating the energy metabolism and correcting the polarization of macrophages through activation of AMP-activated protein kinase(AMPK)and inhibition of hypoxia inducible factor 1α(HIF-1α).METHODS AA rats were treated with BBR(40,80,or 160 mg·kg-1)from days 15 to 29 after immunization.The histopathology of ankle joint was examined through hematoxylin-eosin(HE)staining.The concentrations of tumour necrosis factor-α(TNF-α),interleukin-6(IL-6),IL-1β,IL-2,IL-17A,interferon-gamma(IFN-γ),monocyte chemotactic protein 1(MCP-1),IL-4,IL-10,transforming growth factor-β1(TGF-β1),ATP,and lactic acid were measured by using ELISA kits.The percentage of M1 and M2 macro⁃phage cells in joint tissues were evaluated by immune-fluorescence.The expressions of p-AMPK and HIF-1αin joint of AA rats were determined according to immunohistochemistry analysis.The migration of macrophage was detected by Transwell assays.The expression of inducible nitric oxide synthase(iNOS),Arginase-1(Arg1),p-AMPK,AMPK and HIF-1αwere examined by Western blotting.The labeled macrophages were observed with laser confocal microscopy.RESULTS BBR relieved signs and symptoms of AA rats and reversed pathological changes.BBR treatment group exhibited decreases in pro-inflammatory cytokines(TNF-α,IL-1β,IL-6,IL-2,IL-17A,IFN-γ,and MCP-1)coupled with increases anti-inflammatory cytokines(IL-4,IL-10,TGF-β1)in the serum.The number of M1 macrophage was reduced,while the number of M2 macrophage was increased in BBR group joint tissues.Moreover,BBR showed marked up-regu⁃lation the expression of p-AMPK and down-regulation the expression of HIF-1αin joint of AA rats.Next in vitro study,we found BBR up-regulated the expression of p-AMPK,Arg1(M2 marker)and down-regulated the expression of HIF-1α,iNOS(M1 marker)induced by LPS in peritoneal macrophages from normal SD rat.Furthermore,BBR treatment inhibited the migration of macrophages stimulated by LPS.The level of ATP was elevated and lactic acid was reduced in LPSinduced macrophages after treated by BBR.However,Compound C significantly attenuated the effects of BBR on acti⁃vated macrophages.CONCLUSION BBR alleviates inflammation by regulating energy metabolism and correcting the polarization of macrophage through AMPK-HIF-1αpathway.BBR might have great therapeutic value for RA.

Effects of biological clock gene BMAL1 and hypoxia-inducible factor HIF-1αon proliferation,migration and radiotherapy sensitivity of nasopharyngeal carcinoma cells HONE1

Objective To understand the effects of clock gene BMAL1 and HIF-1α(Hypoxia inducible factor-1α)on proliferation,migration and sensitivity to radiotherapy of nasopharyngeal carcinoma cells HONE1.At the same time,whether the biological clock gene BMAL1 can affect the expression of HIF-1αprotein was investigated.It will lay the foundation for further study on the correlation between clock gene BMAL1 and HIF pathway.Methods BMAL1 gene overexpression and interference lentivirus and HIF-1αgene interference lentivirus were constructed respectively,and were transfected into nasopharyngeal carcinoma cells HONE1.Western blot was used to verify the establishment of overexpressed and knockdown BMAL1 cell lines and HIF-1αgene knockdown cell line,and to investigate the expression of HIF-1αprotein in overexpressed and knockdown BMAL1 cell lines.CCK-8 cell proliferation test and scratch test were used to analyze the proliferation and migration ability of cells.Cell apoptosis after radiotherapy was analyzed by flow cytometry.The effects of BMAL1 and HIF-1αon the sensitivity of HONE1 radiotherapy in nasopharyngeal carcinoma cells after X-ray irradiation at different doses(0Gy,2Gy,4Gy,6Gy)were detected by clone formation assay.Results The overexpression of BMAL1 gene and lentivirus interference were constructed to effectively up regulate and down regulate the expression of BMAL1 protein in nasopharyngeal carcinoma cells HONE1.Meanwhile,HIF-1αgene interference lentivirus was constructed to effectively down-regulate the expression of HIF-1αprotein in nasopharyngeal carcinoma cell line HONE1,and successfully screen out stable nasopharyngeal carcinoma cell lines.Western blot results showed that overexpression of BMAL1 gene could inhibit the expression of HIF-1αprotein in HONE1 of nasopharyngeal carcinoma cells,while knockdown of BMAL1 gene promoted the expression of HIF-1αprotein in HONE1 of nasopharyngeal carcinoma cells(P<0.05).CCK-8 cell proliferation and scratch test showed that overexpression of BMAL1 gene or knockdown of HIF-1αgene could inhibit the proliferation and migration of HONE1 cells(P<0.05).Flow cytometry results showed that after 8Gy irradiation for 72 h,the apoptosis rate of BMALl gene overexpression group was higher than that of the overexpression control group,similarly,the apoptosis rate of HIF-1αgene knockdown group was higher than that of the knockdown control group(P<0.05).After X-ray irradiation at different doses(0Gy,2Gy,4Gy,6Gy),clon-formation experiment showed that the clon-formation rate and cell survival fraction of BMALl overexpression group or HIF-1αknockdown group were lower than those of negative control group(P<0.05).Sigmaplot analysis showed that the D0,Dq and SF2 of the BMAL1 overexpression group or HIF-1αknockdown group were lower than those of the negative control group,and the radiosensitization ratios were 1.381 and 1.063,respectively.Conclusion Overexpression of BMAL1 gene can inhibit the proliferation and migration of nasopharyngeal carcinoma cell line HONE1,increase apoptosis after radiotherapy and improve radiosensitivity.Knock down HIF-1αGene can inhibit the proliferation and migration of nasopharyngeal carcinoma cell line HONE1,increase apoptosis after radiotherapy and improve radiosensitivity.In nasopharyngeal carcinoma cells HONE1,overexpression of BMAL1 gene can inhibit the expression of HIF-1αprotein while knockdown of BMAL1 gene can promote the expression of HIF-1αprotein.

Epigenetic Tumor Response to Hypoxia: An Epimutation Pattern and a Method of Multi Targeted Epigenetic Therapy (MTET)

In most cases, cancer develops as a result of non-inheritable somatic mutations (epimutations), acquired by the individual adult cell, during the evolution of the cell, and propagated into an expanding clone of progeny of the cells by natural selection [1]. The role of microenvironment in selection for such acquired mutations, or epimutations, is a focus of scientific research in carcinogenesis [2]. Here we describe a defective DNA response to hypoxia due to epigenetic aberrancies, in cancer cellular biology [3]. We also summarize a literature review on hypoxia mediated epigenetic responses, and its role in carcinogenesis and metastasis. Further, we review a novel method of treating hypoxic solid tumors with a combination of epigenetic modifiers with both in vitro and in vivo results in human, translating to an improved prognosis and clinical outcome. We propose that this approach both independently and synergistically (with the current standard of care) can provide an improved outcome.

Targeted anti-cancer therapy: Co-delivery of VEGF siRNA and Phenethyl isothiocyanate (PEITC) via cRGD-modified lipid nanoparticles for enhanced anti-angiogenic efficacy

Anti-tumor angiogenesis therapy, targeting the suppression of blood vessel growth in tumors, presents a potent approach in the battle against cancer. Traditional therapies have primarily concentrated on single-target techniques, with a specific emphasis on targeting the vascular endothelial growth factor, but have not reached ideal therapeutic efficacy. In response to this issue, our study introduced a novel nanoparticle system known as CS-siRNA/PEITC&L-cRGD NPs. These chitosan-based nanoparticles have been recognized for their excellent biocompatibility and ability to deliver genes. To enhance their targeted delivery capability, they were combined with a cyclic RGD peptide (cRGD). Targeted co-delivery of gene and chemotherapeutic agents was achieved through the use of a negatively charged lipid shell and cRGD, which possesses high affinity for integrin αvβ3 overexpressed in tumor cells and neovasculature. In this multifaceted approach, co-delivery of VEGF siRNA and phenethyl isothiocyanate (PEITC) was employed to target both tumor vascular endothelial cells and tumor cells simultaneously. The co-delivery of VEGF siRNA and PEITC could achieve precise silencing of VEGF, inhibit the accumulation of HIF-1α under hypoxic conditions, and induce apoptosis in tumor cells. In summary, we have successfully developed a nanoparticle delivery platform that utilizes a dual mechanism of action of anti-tumor angiogenesis and pro-tumor apoptosis, which provides a robust and potent strategy for the delivery of anti-cancer therapeutics.

Role of abnormal lipid metabolism in development,progression,diagnosis and therapy of pancreatic cancer

There is growing evidence that metabolic alterations play an important role in cancer development and progression.The metabolism of cancer cells is reprogrammed in order to support their rapid proliferation.Elevated fatty acid synthesis is one of the most important aberrations of cancer cell metabolism.An enhancement of fatty acids synthesis is required both for carcinogenesis and cancer cell survival,as inhibition of key lipogenic enzymes slows down the growth of tumor cells and impairs their survival.Based on the data that serum fatty acid synthase(FASN),also known as oncoantigen 519,is elevated in patients with certain types of cancer,its serum level was proposed as a marker of neoplasia.This review aims to demonstrate the changes in lipid metabolism and other metabolic processes associated with lipid metabolism in pancreatic ductal adenocarcinoma(PDAC),the most common pancreatic neoplasm,characterized by high mortality.We also addressed the influence of some oncogenic factors and tumor suppressors on pancreatic cancer cell metabolism.Additionally the review discusses the potential role of elevated lipid synthesis in diagnosis and treatment of pancreatic cancer.In particular,FASN is a viable candidate for indicator of pathologic state,marker of neoplasia,as well as,pharmacological treatment target in pancreatic cancer.Recent research showed that,in addition to lipogenesis,certain cancer cells can use fatty acids from circulation,derived from diet(chylomicrons),synthesized in liver,or released from adipose tissue for their growth.Thus,the interactions between de novo lipogenesis and uptake of fatty acids from circulation by PDAC cells require further investigation.

Cardiovascular abnormalities of long-COVID syndrome:Pathogenic basis and potential strategy for treatment and rehabilitation

Cardiac injury and sustained cardiovascular abnormalities in long-COVID syndrome,i.e.post-acute sequelae of coronavirus disease 2019(COVID-19)have emerged as a debilitating health burden that has posed challenges for management of pre-existing cardiovascular conditions and other associated chronic comorbidities in the most vulnerable group of patients recovered from acute COVID-19.A clear and evidence-based guideline for treating cardiac issues of long-COVID syndrome is still lacking.In this review,we have summarized the common cardiac symptoms reported in the months after acute COVID-19 illness and further evaluated the possible pathogenic factors underlying the pathophysiology process of long-COVID.The mechanistic understanding of how Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2)damages the heart and vasculatures is critical in developing targeted therapy and preventive measures for limiting the viral attacks.Despite the currently available therapeutic interventions,a considerable portion of patients recovered from severe COVID-19 have reported a reduced functional reserve due to deconditioning.Therefore,a rigorous and comprehensive cardiac rehabilitation program with individualized exercise protocols would be instrumental for the patients with long-COVID to regain the physicalfitness levels comparable to their pre-illness baseline.

Mitochondrial control of hematopoietic stem cell balance and hematopoiesis

Hematopoietic stem cells （HSCs） are stem cells from mesodermal derivation that reside in bone marrow and provide blood cells for the whole life of an adult individual, through a process called hematopoiesis. The long lasting support of HSCs for hematopoiesis is permitted by the fine regulation of quiescence and division output. Exit from the quiescent state is to produce a committed and/or stem daughter cells, in an event defined asymmetric or symmetric division. A deregulation in the proportion between asymmetric and symmetric divisions is critical in the appearance of hematological disorders ranging from bone marrow failure to hematological malignancies. Over the past years, several studies have indicated how the metabolism of HSCs is determinant in the regulation of HSC quiescence and commitment process. A metabolism shifted to the glycolytic pathway promotes HSCs quiescence and sustainment of hematopoiesis. Boosting mitochondrial respiration promotes the stem cell commitment followed by stem pool exhaustion, and minimal mitochondrial activity is required to maintain the HSCs quiescence. In the present review are discussed the most recent advances in comprehension of the roles of mitochondria in the hematopoiesis and in the division balance.