Prevention of acquired sensorineural hearing loss in mice by in vivo Htra2 gene editing

BACKGROUND

Aging, noise, infection, and ototoxic drugs are the major causes of human acquired sensorineural hearing loss, but treatment options are limited. CRISPR/Cas9 technology has tremendous potential to become a new therapeutic modality for acquired non-inherited sensorineural hearing loss. Here, we develop CRISPR/Cas9 strategies to prevent aminoglycoside-induced deafness, a common type of acquired non-inherited sensorineural hearing loss, via disrupting the Htra2 gene in the inner ear which is involved in apoptosis but has not been investigated in cochlear hair cell protection.

RESULTS

The results indicate that adeno-associated virus (AAV)-mediated delivery of CRISPR/SpCas9 system ameliorates neomycin-induced apoptosis, promotes hair cell survival, and significantly improves hearing function in neomycin-treated mice. The protective effect of the AAV-CRISPR/Cas9 system in vivo is sustained up to 8 weeks after neomycin exposure. For more efficient delivery of the whole CRISPR/Cas9 system, we also explore the AAV-CRISPR/SaCas9 system to prevent neomycin-induced deafness. The in vivo editing efficiency of the SaCas9 system is 1.73% on average. We observed significant improvement in auditory brainstem response thresholds in the injected ears compared with the non-injected ears. At 4 weeks after neomycin exposure, the protective effect of the AAV-CRISPR/SaCas9 system is still obvious, with the improvement in auditory brainstem response threshold up to 50 dB at 8 kHz.

CONCLUSIONS

These findings demonstrate the safe and effective prevention of aminoglycoside-induced deafness via Htra2 gene editing and support further development of the CRISPR/Cas9 technology in the treatment of non-inherited hearing loss as well as other non-inherited diseases.

p53 mediated transcription of Omi/HtrA2 in aging myocardium

AIMS

Omi/HtrA2 is a pro-apoptotic protein, increased mRNA and protein levels of Omi/HtrA2 in aging myocardium facilitates apoptosis and affects mitochondrial homeostasis. Our previous study found that p53 can bind to the Omi/HtrA2 promoter. The purpose of this study was to determine whether p53 participates in regulating the expression of Omi/HtrA2 in aging myocardium.

METHODS AND RESULTS

we used Western blot to detect the expression of Omi/HtrA2 and p53 nucleoprotein, and then found that both of them were elevated in aging heart. Furthermore, we also observed the increased binding of p53 to Omi/HtrA2 promoter by chromatin immunoprecipitation. To initially explore the regulation mechanism of Omi/HtrA2, plasmid transfection and RNA interference in NIH3T3 cells were used to upregulate or knock down p53, respectively. The mRNA and protein levels of Omi/HtrA2 were increased with the overexpression of p53 by real-time PCR and Western blot, and Omi/HtrA2 promoter activity enhanced after transfected with pcDNA3.1-p53. The result from RNA interference was quite the contrary.Our study demonstrated that the binding ability of p53 to Omi/HtrA2 promoter was increased in aging myocardium, and increased p53 promoted the mRNA and protein levels of Omi/HtrA2 by enhancing the promoter activity of Omi/HtrA2.

CONCLUSIONS

p53 acts as a transcriptional factor that induces Omi/HtrA2 expression in aged cardiomyocytes.These results provide a new way to explore the mechanism of increased Omi/HtrA2 in the aging process of heart.

Heat shock factor 1-mediated transcription activation of Omi/HtrA2 induces myocardial mitochondrial apoptosis in the aging heart

BACKGROUND

Increased cardiac apoptosis is a hallmark of the elderly, which in turn increases the risk for developing cardiac disease. The overexpression of Omi/HtrA2 mRNA and protein contributes to apoptosis in the aged heart. Heat shock factor 1 (HSF1) is a transcription factor that binds to the promoter of Omi/HtrA2 in the aging myocardium. However, whether HSF1 participates in cardiomyocyte apoptosis via transcriptional regulation of Omi/HtrA2 remains unclear. The present study was designed to investigate whether HSF1 plays a role in Omi/HtrA2 transcriptional regulation and myocardial apoptosis.

METHODS AND RESULTS

Assessment of the hearts of mice of different ages was performed, which indicated a decrease in cardiac function reserve and an increase in mitochondrial apoptosis. Omi/HtrA2 overexpression in the elderly was negatively correlated with left ventricular function after exercise overload and positively correlated with myocardial Caspase-9 apoptosis. Chromatin immunoprecipitation (ChIP) of aging hearts and plasmid transfection/RNA interference of H9C2 cells revealed that enhancement of HSF1 expression promotes Omi/HtrA2 expression by inducing the promoter activity of Omi/HtrA2 while also increasing mitochondrial apoptosis by upregulating Omi/HtrA2 expression.

CONCLUSIONS

HSF1 acts as a transcriptional factor that induces Omi/HtrA2 expression and Caspase-9 apoptosis in aged cardiomyocytes, while also decreasing cardiac function reserve.

Omi/HtrA2 Protease Associated Cell Apoptosis Participates in Blood-Brain Barrier Dysfunction

Background: Omi/HtrA2 is a proapoptotic mitochondrial serine protease involved in caspase-dependent cell apoptosis, translocating from mitochondria to the cytosol after an apoptotic insult. Our previous study indicated pre-treatment with UCF-101, a specific inhibitor of Omi/HtrA2, could significantly reduce neuronal apoptosis and attenuate sepsis-induced cognitive dysfunction. Various hypotheses involving blood-brain-barrier (BBB) disruption have been proposed to account for sepsis-associated encephalopathy (SAE). Here, we attempted to explore whether interference of Omi/HtrA2 by RNA interference or UCF-101 pre-treatment can improve sepsis-induced disruption of BBB using human cerebral microvascular endothelial cell line (hCMEC/D3) in vitro and if so, to explore mechanisms involved Omi/HtrA2 protease mediates BBB disruption in SAE.

Methods: hCMEC/D3 cell monolayers were intervened by different concentrations of LPS (0–50 μg/mL) over experimental period. Pharmacological or gene interventions (by silencing RNA of Omi/HtrA2) were used to study molecular mechanisms involved in sepsis-associated Omi/HtrA2 translocation, cell apoptosis and BBB dysfunction. BBB function was assessed by trans-endothelial electrical resistance (TEER) and permeability to labeled dextrans (FITC-4kDa). Tight junction (TJ) integrity was assessed by immunofluorescence, western blotting and transmission electron microscopic (TEM) analyses. Apoptosis was determined using flow cytometry and TUNEL assay. Mitochondrial membrane potential (MMP) and oxidative stress were also investigated.

Results: LPS affects hCMEC/D3 TJ permeability in a concentration- and time-dependent manner. LPS intervention resulted in a significant disruption of BBB, as manifested by decreased TEER (by ~26%) and a parallel increased paracellular permeability to FITC- (4kDa) dextrans through hCMEC/D3 monolayers. The inhibition of Omi/HtrA2 by UCF-101 or Omi/HtrA2 shRNA reduced LPS-induced brain endothelial cell apoptosis, and resulted in significant improvement on LPS-induced BBB disruption as well as decreased occludin, claudin-5 and ZO-1 expressions. Omi/HtrA2 manipulated endothelial cell apoptosis by shifting into cytosol and inducing X-linked inhibitor of apoptosis protein (XIAP) degradation. UCF-101 administration or Omi/HtrA2 shRNA intervention did attenuate the degradation of XIAP, Poly ADP-ribose polymerase (PARP) cleavage, and caspase-3 cleavage. However, only UCF-101 partly prevented the mobilization of Omi/HtrA2 from the mitochondria to the cytosol after LPS intervention. That abrogation of Omi/HtrA2 by UCF-101 or Omi/HtrA2 shRNA resulted in a significant improvement on LPS-induced decrease of MMP. Oxidative stress was significantly increased in the LPS treated group compared to the control or NC-shRNA group. However, abrogation of Omi/HtrA2 by UCF-101 or Omi/HtrA2 shRNA did not significantly improve oxidative injury.

Conclusions: Our study indicated an important role of Omi/HtrA2 in manipulating LPS-induced cell apoptosis and BBB integrity by translocating from mitochondria into cytosol in brain endothelial cells. Omi/HtrA2 induced mitochondrial pathway apoptosis, which involves inhibition of an important antiapoptotic protein XIAP and influence on MMP. Therapeutic methods that inhibit Omi/HtrA2 function may provide a novel therapeutic measure to septic encephalopathy.

Omi/HtrA2 Participates in Age-Related Autophagic Deficiency in Rat Liver

Liver is a vital organ with many important functions, and the maintenance of normal hepatic function is necessary for health. As an essential mechanism for maintaining cellular homeostasis, autophagy plays an important role in ensuring normal organ function. Studies have indicated that the degeneration of hepatic function is associated with autophagic deficiency in aging liver. However, the underlying mechanisms still remain unclear. The serine protease Omi/HtrA2 belongs to the HtrA family and promotes apoptosis through either the caspase-dependent or caspase-independent pathway. Mice lacking Omi/HtrA2 exhibited progeria symptoms (premature aging), which were similar to the characteristics of autophagic insufficiency. In this study, we demonstrated that both the protein level of Omi/HtrA2 in liver and hepatic function were reduced as rats aged, and there was a positive correlation between them. Furthermore, several autophagy-related proteins (LC3II/I, Beclin-1 and LAMP2) in rat liver were decreased significantly with the increasing of age. Finally, inhibition of Omi/HtrA2 resulted in reduced autophagy and hepatic dysfunction. In conclusion, these results suggest that Omi/HtrA2 participates in age-related autophagic deficiency in rat liver. This study may offer a novel insight into the mechanism involved in liver aging.

Increased Expression of Apo-J and Omi/HtrA2 After Intracerebral Hemorrhage in Rats

OBJECTIVE

To investigate the changes of Apo-J and Omi/HtrA2 protein expression in rats with intracerebral hemorrhage.

METHODS

150 Sprague-Dawley adult rats were randomly divided into 3 groups: (1) normal control (NC) group, (2) sham group, and (3) intracerebral hemorrhage (ICH) group. The data were collected at 6 hours, 12 hours, 1 day, 2 days, 3 days, 5 days, and 7 days. Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated biotinylated-dUTP nick-end labeling staining. The distributions of the Apo-J and Omi/HtrA2 proteins were determined by immunohistochemical staining. The levels of Apo-J mRNA and Omi/HtrA2 mRNA expressions were examined by real-time polymerase chain reaction.

RESULTS

Apoptosis in the ICH group was higher than in the sham and NC groups (P < 0.05). Both the Apo-J and Omi/HtrA2 expression levels were increased in the peripheral region of hemorrhage, with a peak at 3 days. The Apo-J mRNA level positively correlated with the HtrA2 mRNA level in the ICH group (r = 0.883, P < 0.001).

CONCLUSION

The expressions of Apo-J and Omi/HtrA2 increased in parallel in the peripheral region of rat cerebral hemorrhage. Local high expression of Apo-J in the peripheral regions may play a neuroprotective role by inhibiting apoptosis via the Omi/HtrA2 pathway after hemorrhage.

TrkAIII signals endoplasmic reticulum stress to the mitochondria in neuroblastoma cells, resulting in glycolytic metabolic adaptation. Oncotarget. 2018;9:8368-8390. [PMID: 29492201 PMCID: PMC5823587 DOI: 10.18632/oncotarget.23618]

Alternative TrkAIII splicing characterises advanced stage metastatic disease and post-therapeutic relapse in neuroblastoma (NB), and in NB models TrkAIII exhibits oncogenic activity. In this study, we report a novel role for TrkAIII in signaling ER stress to the mitochondria in SH-SY5Y NB cells that results in glycolytic metabolic adaptation. The ER stress-inducing agents DTT, A23187 and thapsigargin activated the ER stress-response in control pcDNA SH-SY5Y and TrkAIII expressing SH-SY5Y cells and in TrkAIII SH-SY5Y cells increased TrkAIII targeting to mitochondria and internalisation into inner-mitochondrial membranes. Within inner-mitochondrial membranes, TrkAIII was subjected to Omi/HtrA2-dependent cleavage to tyrosine phosphorylated 45–48kDa carboxyl terminal active fragments, localised predominantly in tyrosine kinase-domain mitochondrial matrix orientation. This stress-induced activation of mitochondrial TrkAIII was associated with increased ROS production, prevented by the ROS scavenger Resveratrol and underpinned by changes in Ca2+ movement, implicating ROS/Ca2+ interplay in overcoming the mitochondrial TrkAIII activation threshold. Stress-induced, cleavage-activation of mitochondrial TrkAIII resulted in mitochondrial PDHK1 tyrosine phosphorylation, leading to glycolytic metabolic adaptation. This novel mitochondrial role for TrkAIII provides a potential self-perpetuating, drug reversible way through which tumour microenvironmental stress may maintain the metastasis promoting “Warburg effect” in TrkAIII expressing NBs.

Familial Parkinson's Disease-Associated L166P Mutant DJ-1 is Cleaved by Mitochondrial Serine Protease Omi/HtrA2

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Mutations in the DJ-1, including L166P, are responsible for recessive early-onset PD. Many lines of evidence have shown that L166P is not only a loss-of-function mutant, but also a pro-apoptotic-like protein that results in mitochondrial dysfunction. L166P has been reported to be unstable and to mislocalize to mitochondria. However, the mechanisms underlying the instability of L166P compared to wild-type DJ-1 remain largely unknown. Here, we showed that Omi/HtrA2, a mitochondrial serine protease that has also been linked to the pathogenesis of PD, contributed to L166P instability. Omi directly interacted with and cleaved L166P in mitochondria to decrease the L166P level. However, Omi did not bind and cleave wild-type DJ-1. Moreover, Omi cleaved L166P at both serine residues 3 and 121, while L166P-induced cell death under H₂O₂ treatment was alleviated by over-expression of Omi. Our data reveal a bridge between DJ-1 and Omi, two PD-associated genetic factors, which contributes to our understanding of the pathogenesis of PD.

Mitochondrial Omi/HtrA2 Promotes Caspase Activation Through Cleavage of HAX-1 in Aging Heart

Mitochondrial homeostasis is a key process involved in cellular destiny and organic function. When mitochondrial status is abnormal, it will become a "death motor." Impaired mitochondria lead to the release of cytochrome c, and then trigger mitochondria-induced caspase activation. Omi/HtrA2, a serine protease, locates in mitochondria and involves in mitochondrial homeostasis. Increased Omi/HtrA2 is observed in aging cardiac tissues, and whether this has effects on mitochondrial status has not been reported. In this study, natural Sprague-Dawley rats (22 months) were used. We detected markedly increased proteolytic activity of Omi/HtrA2 and obvious activation of caspase-9 and caspase-3 in their myocardium. Then, we constructed stably transfected mitochondrial Omi/HtrA2 cells, and decreased mitochondrial membrane potential was detected by JC-1 (a probe for mitochondria) and tetramethylrhodamine methyl ester (TMRM) dyeing and significant release of cytochrome c was observed after separation of mitochondrial fraction and cytosolic fraction. Furthermore, ucf-101 (a special inhibitor of Omi/HtrA2) and HAX-1 siRNA could ameliorate those phenomena above. In conclusion, excessive Omi/HtrA2 in mitochondria induced decreased mitochondrial membrane potential by its proteolytic activity, followed by cytochrome c released from mitochondria into cytosol where cytochrome c promoted caspase activation. Also, Omi/HtrA2-HAX-1 chain played a significant role in mitochondrial homeostasis.

Cloning and Transcriptional Activity of the Mouse Omi/HtrA2 Gene Promoter

HtrA serine peptidase 2 (HtrA2), also named Omi, is a pro-apoptotic protein that exhibits dramatic changes in expression levels in a variety of disorders, including ischemia/reperfusion injury, cancer, and neurodegeneration. In our study, Omi/HtrA2 protein levels were high in the heart, brain, kidney and liver, with elevated heart/brain expression in aging mice. A similar expression pattern was observed at the mRNA level, which suggests that the regulation of Omi/HtrA2 is predominately transcriptional. Promoter binding by transcription factors is the main influencing factor of transcription, and to identify specific promoter elements that contribute to the differential expression of mouse Omi/HtrA2, we constructed truncated Omi/HtrA2 promoter/luciferase reporter vectors and analyzed their relative luciferase activity; it was greatest in the promoter regions at -1205~-838 bp and -146~+93 bp, with the -838~-649 bp region exhibiting negative regulatory activity. Bioinformatics analysis suggested that the Omi/HtrA2 gene promoter contains a CpG island at -709~+37 bp, and eight heat shock transcription factor 1 (HSF1) sites, two Sp1 transcription factor (SP1)sites, one activator protein (AP) site, seven p53 sites, and four YY1 transcription factor(YY1) sites were predicted in the core areas. Furthermore, we found that p53 and HSF1 specifically binds to the Omi/HtrA2 promoter using chromatin immunoprecipitation analysis. These results provide a foundation for understanding Omi/HtrA2 regulatory mechanisms, which could further understanding of HtrA-associated diseases.

The cytotoxic and pro-apoptotic activities of the novel fluoropyrimidine F10 towards prostate cancer cells are enhanced by Zn(2+) -chelation and inhibiting the serine protease Omi/HtrA2

BACKGROUND

Intracellular Zn(2+) levels decrease during prostate cancer progression and agents that modulate intracellular Zn(2+) are cytotoxic to prostate cancer cells by an incompletely described mechanism. F10 is a new polymeric fluoropyrimidine drug-candidate that displays strong activity with minimal systemic toxicity in pre-clinical models of prostate cancer and other malignancies. The effects of exogenous Zn(2+) or Zn(2+) chelation for enhancing F10 cytotoxicity are investigated as is the role of Omi/HtrA2, a serine protease that promotes apoptosis in response to cellular stress.

METHODS

To test the hypothesis that the pro-apoptotic effects of F10 could be enhanced by modulating intracellular Zn(2+) we investigated cell-permeable and cell-impermeable Zn(2+) chelators and exogenous Zn(2+) and evaluated cell viability and apoptosis in cellular models of castration-resistant prostate cancer (CRPC; PC3, C4-2). The role of Omi/HtrA2 for modulating apoptosis was evaluated by pharmacological inhibition and Western blotting.

RESULTS

Exogenous Zn(2+) initially reduced prostate cancer cell viability but these effects were transitory and were ineffective at enhancing F10 cytotoxicity. The cell-permeable Zn(2+) -chelator tetrakis-(2-pyridylmethl) ethylenediamine (TPEN) induced apoptosis in prostate cancer cells and enhanced the pro-apoptotic effects of F10. The pro-apoptotic effects of Zn(2+) -chelation in combination with F10 treatment were enhanced by inhibiting Omi/HtrA2 implicating this serine protease as a novel target for prostate cancer treatment.

CONCLUSIONS

Zn(2+) -chelation enhances the pro-apoptotic effects of F10 and may be useful for enhancing the effectiveness of F10 for treatment of advanced prostate cancer. The serine protease Omi/HtrA2 modulates Zn(2+) -dependent apoptosis in prostate cancer cells and represents a new target for treatment of CRPC. Prostate 75:360-369, 2015. © 2014 Wiley Periodicals, Inc.

Inactivation of Omi/HtrA2 protease leads to the deregulation of mitochondrial Mulan E3 ubiquitin ligase and increased mitophagy

Omi/HtrA2 is a nuclear encoded mitochondrial serine protease with dual and opposite functions that depend entirely on its subcellular localization. During apoptosis, Omi/HtrA2 is released into the cytoplasm where it participates in cell death. While confined in the inter-membrane space of the mitochondria, Omi/HtrA2 has a pro-survival function that may involve the regulation of protein quality control (PQC) and mitochondrial homeostasis. Loss of Omi/HtrA2's protease activity causes the neuromuscular disorder of the mnd2 (motor neuron degeneration 2) mutant mice. These mice develop multiple defects including neurodegeneration with parkinsonian features. Loss of Omi/HtrA2 in non-neuronal tissues has also been shown to cause premature aging. The normal function of Omi/HtrA2 in the mitochondria and how its deregulation causes neurodegeneration or premature aging are unknown. Here we report that the mitochondrial Mulan E3 ubiquitin ligase is a specific substrate of Omi/HtrA2. During exposure to H(2)O(2), Omi/HtrA2 degrades Mulan, and this regulation is lost in cells that carry the inactive protease. Furthermore, we show accumulation of Mulan protein in various tissues of mnd2 mice as well as in Omi/HtrA2(-/-) mouse embryonic fibroblasts (MEFs). This causes a significant decrease of mitofusin 2 (Mfn2) protein, and increased mitophagy. Our work describes a new stress-signaling pathway that is initiated in the mitochondria and involves the regulation of Mulan by Omi/HtrA2 protease. Deregulation of this pathway, as it occurs in mnd2 mutant mice, causes mitochondrial dysfunction and mitophagy, and could be responsible for the motor neuron disease and the premature aging phenotype observed in these animals.