Acidic Environment Induces Pyroptosis of NLRP3 Inflammatory Vesicle-Mediated Nucleus Pulposus Cells Through Up-Regulation of POSTN Expression

SUMMARY: Intervertebral disc degeneration (IVDD) is induced by nucleus pulposus (NP) dysfunction as a result of massive loss of NP cells. It has been reported that the acidic microenvironment of the intervertebral disc (IVD) can induce NP cell pyroptosis, and that up-regulation of periostin (POSTN) expression has a negative effect on NP cell survival. However, the relationship between the acidic environment, POSTN expression level and NP cell pyroptosis is unclear. Therefore, the aim of this study was to explore the relationship between acidic environment and POSTN expression level in NP cells, as well as the effect of POSTN in acidic environment on NP cell pyroptosis. NP cells were obtained from the lumbar vertebrae of Sprague Dawley (SD) male rats. These cells were divided into normal and acidic groups according to whether they were exposed to 6 mM lactic acid solution. And NP cells in the acidic group were additionally divided into three groups: (1) Blank group: no transfection; (2) NC group: cells transfected with empty vector plasmid; (3) sh-POSTN group: cells transfected with sh-POSTN plasmid to knock down the expression level of POSTN. Quantitative real-time PCR (qRT-PCR) and western blot was performed to assess the expression of POSTN at the mRNAand protein levels. CCK8 was used to evaluate cell survival. Western blot, in addition, was performed to examine acid-sensing ion channels (ASIC)-related proteins. And pyroptosis was detected by ELISA and western blot. The expression level of POSTN was significantly increased in NP cells in acidic environment. Knockdown of POSTN expression promoted the survival of NP cells in acidic environment and reduced the protein levels of ASIC3 and ASIC1a in NP cells. Moreover, knockdown of POSTN expression decreased the pyroptosis proportion of NP cells and the levels of pro-inflammatory cytokines interleukin (IL)-1β and IL-18. The levels of pyroptosis-related proteins NLRP3, ASC, cleaved-Caspase-1, and cleaved-GSDMD were also affected by the decreased POSTN expression. The extracellular acidic environment created by lactic acid solution activated NLRP3 inflammatory vesicle-induced caspase-1 to get involved in NP cell pyroptosis by up-regulating POSTN expression.

La degeneración del disco intervertebral (DDIV) es inducida por una disfunción del núcleo pulposo (NP) como resultado de una pérdida masiva de células NP. Se ha informado que el microambiente ácido del disco intervertebral (DIV) puede inducir la piroptosis de las células NP y que la regulación positiva de la expresión de periostina (POSTN) tiene un efecto negativo en la supervivencia de las células NP. Sin embargo, la relación entre el ambiente ácido, el nivel de expresión de POSTN y la piroptosis de las células NP es poco clara. Por lo tanto, el objetivo de este estudio fue explorar la relación entre el ambiente ácido y el nivel de expresión de POSTN en células NP, así como el efecto de POSTN en ambiente ácido sobre la piroptosis de las células NP. Las células NP se obtuvieron de las vertebras lumbares de ratas macho Sprague Dawley (SD). Estas células se dividieron en grupos normales y ácidos según se expusieron a una solución de ácido láctico 6 mM. Las células NP en el grupo ácido se dividieron adicionalmente en tres grupos: (1) Grupo en blanco: sin transfección; (2) grupo NC: células transfectadas con plásmido vector vacío; (3) grupo sh-POSTN: células transfectadas con plásmido sh-POSTN para reducir el nivel de expresión de POSTN. Se realizó una PCR cuantitativa en tiempo real (qRT-PCR) y una transferencia Western para evaluar la expresión de POSTN en los niveles de ARNm y proteína. Se utilizó CCK8 para evaluar la supervivencia celular. Además, se realizó una transferencia Western para examinar las proteínas relacionadas con los canales iónicos sensibles al ácido (ASIC). La piroptosis se detectó mediante ELISA y Western blot. El nivel de expresión de POSTN aumentó significativamente en células NP en ambiente ácido. La eliminación de la expresión de POSTN promovió la supervivencia de las células NP en un ambiente ácido y redujo los niveles de proteína de ASIC3 y ASIC1a en las células NP. Además, la eliminación de la expresión de POSTN disminuyó la proporción de piroptosis de las células NP y los niveles de citocinas proinflamatorias interleucina (IL) - 1β e IL-18. Los niveles de proteínas relacionadas con la piroptosis NLRP3, ASC, Caspasa-1 escindida y GSDMD escindida también se vieron afectados por la disminución de la expresión de POSTN. El ambiente ácido extracelular creado por la solución de ácido láctico activó la caspasa-1 inducida por vesículas inflamatorias NLRP3 para involucrarse en la piroptosis de las células NP mediante la regulación positiva de la expresión de POSTN.

The pH low insertion peptides and their application: research advances / 国际药学研究杂志

Many diseases such as tumor, ischemia and inflammation produce acidic extracellular microenvironment at the lesion site. This extracellular microenvironment also provides a new opportunity for the diagnosis and treatment of these diseases. Acidresponding peptides (pH low insertion peptides, pHLIP) can spontaneously fold into transmembrane helices under acidic microenvironment and insert across cell membranes, providing new opportunities for targeting these acidic tissues. At present, pHLIP has attracted more and more attention in the diagnosis and treatment of diseases. This article summarizes the advances in the pHLIP research from the aspects of the discovery and development, action mechanism and application of pHLIP.

Research situation of pH low insertion peptides / 药学学报

Extracellular acidity has been associated with many pathological states, such as cancer, ischemic stroke, neurotrauma and infection, which makes it an effective target for therapy and diagnosis of such diseases. As a polypeptide vector, pH low insertion peptides (pHLIPs) are endowed with high sensitivity to extracellular acidic environment, which can insert the membrane and deliver payload to pathological cells in a pH dependent manner. Here, theranostic applications of pHLIP in disease, are reviewed in two aspects:pHLIP-mediated single-molecule transporter and nano-sized carrier.

Interaction of dental pulp stem cells with Biodentine and MTA after exposure to different environments

ABSTRACT Objective: The aim of the present study was to evaluate and compare the cytotoxic effects of Biodentine and MTA on dental pulp stem cells (DPSCs) and to assess cell viability and adherence after material exposure to an acidic environment. Material and Methods: DPSCs were cultured either alone or in contact with either: Biodentine; MTA set for 1 hour; or MTA set for 24 hours. After 4 and 7 days, cell viability was measured using the MTT assay. Biodentine and MTA were also prepared and packed into standardized bovine dentin disks and divided into three groups according to the storage media (n=6/group): freshly mixed materials without storage medium (Group A); materials stored in saline (Group B); materials stored in citric acid buffered at pH 5.4 (Group C). After 24 hours, DPSCs were introduced in the wells and cell adherence, viability, and cellular morphology were observed via confocal microscopy after three days of culture. Cell viability was analyzed using repeated-measures analysis of variance test with Tukey's post hoc tests (α=0.05). Results: Biodentine expressed significantly higher cell viability compared with all other groups after 4 days, with no differences after 7 days. Notably, cell viability was significantly greater in 24-hour set MTA compared with 1-hour set MTA and control groups after 7 days. Material exposure to an acidic environment showed an increase in cell adherence and viability in both groups. Conclusions: Biodentine induced a significantly accelerated cell proliferation compared with MTA. Setting of these materials in the presence of citric acid enhanced DPSC viability and adherence.