The PERK-eIF2α branch activates the NLRP3 inflammasome through the NF-κB signaling pathway to suppress NDV replication.

PRAS40 activates the IRE1α-XBP-1-mediated unfolded protein response to exacerbate colorectal cancer by enhancing ST6Gal1-dependent α-2, 6 sialylation of GRP78.

Aging differentially affects disease risks of various organs1. The endocrine organs undergo significant changes along aging. Clinical reports showed increased prevalence of thyroid disorders with age, especially hypothyroidism2. Primary hypothyroidism includes congenital, autoimmune, and iatrogenic causes, which can occur throughout the lifespan. But those with unknown aetiology increase dramatically (~5 fold) in the elderly (≥75 years old)3,4. In thyrocytes, accumulated thyroglobulin requires efficient protein folding in the endoplasmic reticulum (ER)5,6. When ER experiences protein folding defects, it activates the unfolded protein response (UPR), which determines the life-or-death cell fate. The most fundamental mediator in UPR signaling is inositol-requiring enzyme-1 alpha (IRE-1α)7. This study reports, for the first time, a highly conserved gene, Cellular retinoic acid binding protein 1 (Crabp1), critical to thyrocyte function in aging. CRABP1 acts by modulating clustering and activation of IRE-1α, thereby reducing thyrocyte ER stress.

IRE1/FAM134B-mediated ER-phagy alleviates zearalenone-induced ER stress and developmental defects in porcine embryos.

Brucellosis is a widespread zoonotic disease caused by Brucella, a genus of facultative intracellular bacteria that infects livestock and humans. Brucella primarily replicates within the endoplasmic reticulum (ER) of host cells, where it establishes a specialized replicative niche. This ER localization disrupts ER structure and induces ER stress. The unfolded protein response (UPR) is a critical cellular pathway that maintains ER homeostasis by restoring protein-folding capacity and regulating stress responses. However, how Brucella manipulates host UPR pathways to promote its intracellular survival and pathogenesis remains poorly understood. Here, we identify the Brucella outer membrane protein Omp25 as a key factor in promoting its intracellular survival and proliferation by activating the host UPR. Omp25 directly binds to the ER chaperone binding-immunoglobulin protein, inducing the release and activation of the UPR sensors, PKR-like ER kinase, inositol-requiring enzyme 1 alpha, and activating transcription factor 6, thereby modulating ER homeostasis to favor bacterial replication. In addition, Omp25 enhances inflammatory cytokine expression via the binding-immunoglobulin protein-inositol-requiring enzyme 1 alpha-NF-κB signaling axis. The omp25-deleted strains (Δomp25) show impaired intracellular replication and reduced UPR activation and result in attenuated induction of inflammatory genes in infected cells compared with WT strains. In vivo, mice infected with an omp25 mutant strain exhibit lower bacterial burdens and milder tissue pathology compared with mice infected with the WT strain. These findings uncover a mechanism by which Omp25 facilitates Brucella intracellular proliferation through UPR modulation and highlight Omp25 as a potential target for therapeutic interventions and next-generation attenuated vaccines.

Ferroptosis is a regulated form of cell death that serves a pivotal role in tumor suppression. Whilst the ribonuclease activity of inositol-requiring enzyme 1α (IRE1α) is associated with the regulation of ferroptosis, the potential involvement of its kinase domain in this process remains elusive. Thus, the present study aimed to investigate the specific role of the IRE1α kinase domain in regulating ferroptosis in breast cancer, particularly in the triple-negative breast cancer (TNBC) subtype. To this end, it employed a combination of bioinformatic analysis of clinical datasets, pharmacological inhibition of IRE1α kinase and genetic overexpression models in TNBC cell lines. The present study demonstrated that endoplasmic reticulum to nucleus signaling 1 (ERN1; the gene encoding IRE1α) was significantly downregulated in breast cancer compared with that in normal tissues, and that lower ERN1 levels were associated with a worse prognosis of patients with breast cancer. This association persisted in human epidermal growth factor receptor 2-positive and TNBC subtypes. In TNBC, IRE1α kinase inhibitors (APY29 and sunitinib) markedly inhibited ferroptosis induced by system Xc- inhibition. Moreover, by constructing overexpression models of wild-type IRE1α (IRE1α-WT) and a kinase-dead mutant (IRE1α-K599A), it was demonstrated that IRE1α-WT overexpression significantly enhanced sensitivity to ferroptosis, whereas the kinase-dead mutant had no significant effect. Mechanistically, IRE1α kinase inhibition upregulated solute carrier family 7 member 11 (also known as xCT) expression and promoted glutathione (GSH) synthesis, thereby suppressing ferroptosis. Collectively, the present study reveals a new function of IRE1α kinase in the regulation of ferroptosis, highlighting the critical regulatory role of the IRE1α kinase-xCT-GSH axis in ferroptosis in TNBC. Thus, IRE1α kinase may have potential as a therapeutic target.

Dairy cows with ketosis display immune dysfunction and a high incidence of infectious diseases, which may partly be attributed to excessive endoplasmic reticulum stress (ERS) and apoptosis in macrophages. The objective of the present study was to assess the role of ERS in macrophage apoptosis of ketotic dairy cows. Compared with healthy cows, the apoptosis number of macrophages and the protein abundance of glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), and activating transcription factor 6 (ATF6); the ratio of phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK)/PERK, phosphorylated inositol-requiring enzyme 1 (p-IRE1)/IRE1 and phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α)/eIF2α; and mean fluorescence intensity of C/EBP homology protein (CHOP) were greater in cows with clinically ketosis (CK). Treatment with FFA increased protein abundance of GRP78, CHOP, ATF6 and p-IRE1/IRE1, and mean fluorescence intensity of CHOP. Furthermore, FFA increased the protein abundance of cysteinyl aspartate-specific proteinase-3 (Caspase-3) and mean fluorescence intensity of Caspase-3 but decreased the Bcl-2/Bax protein abundance ratio, which was accompanied by an increase in the number macrophage apoptosis. Inhibition of ERS via TUDCA attenuated the increased macrophage apoptosis and the activated apoptotic pathways induced by Tn or FFA. Thus, hyperphysiological concentrations of FFA induce apoptosis in macrophages by triggering ERS in ketotic dairy cows.

This study aimed to compare in vivo cerebral gadolinium (Gd3+) accumulation, associated unfolded protein response (UPR), and oxidative stress parameters in rats after exposure to gadolinium-based contrast agents (GBCAs). This study was designed as a controlled, experimental animal study to evaluate the accumulation of Gd3+ in the basal ganglia of rats following the administration of 0.6 mmol/kg gadopentetate dimeglumine (linear) and gadoterate meglumine (macrocyclic). Male Sprague-Dawley rats were exposed to the contrast agents for 24 and 72 h, and then the basal ganglia tissues were collected postmortem. The tissue levels of Gd3+ accumulation, activating transcription factor-6 (ATF6), inositol-requiring enzyme-1 (IRE-1), protein kinase RNA-like endoplasmic reticulum kinase (PERK), damage-inducible transcript-3 (DDIT3), total antioxidant status (TAS), and total oxidant status (TOS) were determined. Linear GBCA-treated rats had persistent Gd3+ levels over time, whereas a significant reduction from 24 to 72 h was observed in macrocyclic GBCA-treated rats (p < 0.001). PERK, DDIT3, and ATF6 expressions were significantly elevated after linear GBCA exposure (p < 0.05), while no significant increase was observed in the macrocyclic GBCA-treated group. However, IRE-1, TAS, and TOS levels were not significantly different in either group. Linear and macrocyclic GBCAs demonstrated distinct patterns of cerebral Gd3+ accumulation and UPR levels in rats. Accordingly, GBCA administration should be reserved for instances where it is necessary, such as when contrast enhancement is clinically required.

Endoplasmic reticulum stress and the unfolded protein response in ischemic nephropathy: Pathogenic mechanisms and emerging therapeutic strategies.

Concurrent endoplasmic reticulum stress and demyelination in DEHP-exposed zebrafish larvae at the early developmental stages.

Chronic unfolded protein response due to endoplasmic reticulum stress has been proposed as a therapeutic target for hypertension. Here, we tested our hypothesis that inactivation of one of the central unfolded protein response effectors, inositol-requiring enzyme 1α, mitigates hypertension and vascular remodeling in mice infused with angiotensin II. C57BL6 mice were infused with angiotensin II for 2 weeks with or without an inositol-requiring enzyme 1α inhibitor KIRA6 treatment to evaluate blood pressure and cardiovascular remodeling. Mouse small mesenteric arteries were used to assess vascular reactivity. Rat vascular smooth muscle cells were used to assess inositol-requiring enzyme 1α activation, intracellular Ca2+ concentration, and secretory phenotype via proteomics. KIRA6 treatment mitigated hypertension induced by angiotensin II infusion. KIRA6 treatment also prevented angiotensin II-induced vascular thickening and perivascular fibrosis. Immunohistochemical staining of aortas indicated that phosphorylated inositol-requiring enzyme 1α signal in vascular smooth muscle cells was elevated with angiotensin II infusion and attenuated with KIRA6 treatment. Vasoconstriction in small mesenteric arteries after incubation with angiotensin II was attenuated by KIRA6 coincubation. Angiotensin II-induced elevation in intracellular Ca2+ concentration was partially reduced by KIRA6 pretreatment in vascular smooth muscle cells. Proteomic analysis demonstrated that angiotensin II induced a unique secretory phenotype in vascular smooth muscle cells, which was mitigated by KIRA6. Targeting inositol-requiring enzyme 1α is a potential therapy for hypertension and vascular remodeling by reducing vascular resistance, mitigating intracellular Ca2+ elevation, and protecting against secretory phenotype in vascular smooth muscle cells.

Subclinical ketosis in dairy cows is accompanied by adaptive changes in the secretory function of the mammary gland. However, the molecular basis underlying this adaptation remains unclear. The secretory capacity of the mammary gland is closely linked to the activation of the unfolded protein response (UPR) and endoplasmic reticulum (ER) biogenesis, particularly the inositol-requiring enzyme 1α (IRE1α) pathway. Thus, this study aims to investigate whether BHB activates the IRE1α-XBP1 signaling axis to promote ER biogenesis, thereby sustaining casein synthesis. In this study, MAC-T cells were treated with 1.8 mM BHB for 0, 12, 24, or 48 h to mimic subclinical ketotic conditions. We first observed that BHB activated all 3 branches of the UPR without inducing the proapoptotic element of the UPR. Meanwhile, MAC-T cells treated with BHB show a significant increase in ER tracker staining and upregulated mRNA levels of ER biogenesis-related genes, such as choline kinase alpha (CHKA), choline-phosphate cytidylyltransferase alpha (PCYT1A), and Surfeit 4 (SURF4). Subsequently, BHB upregulated the mRNA abundance of genes related to ribosome biogenesis and the proregenerative phenotype in MAC-T cells. The MAC-T cells treated with 1.8 mM BHB also displayed increased protein abundance of β-casein, along with the casein beta (CSN2), casein kappa (CSN3), casein alpha S1 (CSN1S1), and casein alpha S2 (CSN1S2) milk protein genes. Compared with the 1.8 mM BHB group, cotreatment with BHB and KIRA6 significantly suppressed the BHB-induced increase in ER tracker fluorescence, ER biogenesis-related gene expression, and β-casein protein abundance. Silencing XBP1 via small interfering RNA inhibited BHB-induced ER biogenesis and β-casein synthesis, whereas the overexpression of XBP1 alleviated these effects. Furthermore, under BHB treatment, overexpression of XBP1 partially attenuated the suppressive effects of IRE1α inhibition on ER biogenesis and β-casein synthesis. Overall, our data demonstrate that BHB promotes ER biogenesis and milk protein synthesis in mammary epithelial cells through activation of the IRE1α-XBP1 signaling pathway, suggesting a protective and adaptive role for BHB in maintaining mammary gland function under subclinical ketotic conditions.

To investigate therapeutic effects of Huanglian Jiedu Decoction (HLJDD) on metabolic-associated fatty liver disease (MAFLD) and explore its underlying mechanisms. Q-Orbitrap liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify the incoming blood compounds of HLJDD. In vivo, high-fat diet (HFD)-induced MAFLD rats received HLJDD (5.4, 2.7, 1.35 g/kg) or silybin (37.8 mg/kg) once daily for 6 weeks. The rats fed with normal diets were served as control. Serum lipids were biochemically determined; and hepatic steatosis and lipid accumulation were evaluated with H&E and Oil red O stainings. In vitro, palmitic acid (PA)-treated HepG2 cells were co-incubated with 10% HLJDD drug-containing serum. Intracellular triglyceride (TG), total cholesterol (TC) and nonesterified fatty acids (NEFA) levels were detected and lipid droplet changes in HepG2 cells were observed by Oil red O staining. RT-qPCR and Western blot were employed to assess the expressions of lipid metabolic-related genes [diacylglycerol acyltransferase 2 (DGAT2), stearoyl-coenzyme A desaturase 1 (SCD1)] and components of the inositol-requiring enzyme 1alpha/X-box-binding protein-1 spliced (IRE1α/XBP1s) signaling pathway. A total of 43 active compounds of HLJDD were identified. In HFD-fed rats, HLJDD treatment significantly improved hepatic TG and TC and increased HDL-C level (P<0.05 or P<0.01), and also markedly reduced serum levels of TG, TC, LDL-C, ALT, and AST (P<0.05 or P<0.01). H&E and Oil red O stainings further revealed that HLJDD effectively alleviated hepatic steatosis and attenuated lipid accumulation in the liver tissues. In PA-treated HepG2 cells, HLJDD treatment significantly reduced intracellular levels of TG, TC, and NEFA (P<0.05 or P<0.01), as well as lipid accumulation. More importantly, HLJDD treatment exerted therapeutic effects in both HFD-fed rats and PA-induced HepG2 cells by down-regulating lipid metabolic-related genes DGAT2, SCD1 and suppressing the IRE1α/XBP1s pathway related protein expressions (P<0.05 or P<0.01). HLJDD ameliorates MAFLD by modulating lipid metabolism through IRE1α/XBP1s signaling pathway, providing pharmacological evidence for its clinical application.

Small Ubiquitin-Like Modifier 3 Attenuates Lung Ischemia-Reperfusion Injury Progression by Inhibiting Endoplasmic Reticulum Stress through Heat Shock Protein 70.

Chronic hyperglycemia in diabetes elevates oxidative stress, damaging pancreatic β-cells and worsening complications. Oxidative stress also disrupts osteoblast function, suppresses their maturation and triggers apoptosis, thereby contributing to bone fragility. Spironolactone, an aldosterone receptor antagonist prescribed for the treatment of hypertension and heart failure, has potential protective effects on skeletal health. The present study examined whether spironolactone could protect osteoblasts from damage and restore their differentiation under oxidative conditions caused by 2-deoxy-D-ribose (dRib). MC3T3-E1 pre-osteoblastic cells were incubated with spironolactone (0-100 µM) and 15 mM dRib. Cell toxicity (through lactate dehydrogenase release), markers of differentiation (collagen content, alkaline phosphatase activity and mineral deposition), inflammatory cytokine levels (TNF-α and IL-6), reactive oxygen species (ROS), mitochondrial superoxide levels, endoplasmic reticulum (ER) stress markers (activating transcription factor 6 and inositol-requiring enzyme 1), mitochondrial integrity (mitochondrial membrane potential and ATP levels), glyoxalase I activity and reduced glutathione (GSH) levels were analyzed by ELISA. Pretreatment with spironolactone reduced dRib-induced toxicity and improved differentiation markers in MC3T3-E1 cells. It also lowered the elevated cytokine levels, ROS production, mitochondrial oxidative burden and ER stress responses caused by dRib. Furthermore, spironolactone preserved mitochondrial performance and enhanced antioxidant defenses by increasing GSH levels and glyoxalase I activity, thereby promoting the detoxification of harmful byproducts. These findings suggested that spironolactone may protect osteoblasts by mitigating oxidative and inflammatory stress, stabilizing mitochondrial function and enhancing differentiation. Overall, this highlights the possible benefits of spironolactone in the management of diabetes-related bone fragility.

Abstract Ibuprofen (IBU), a widely used nonsteroidal anti-inflammatory drug (NSAID), is associated with hepatotoxic effects, particularly at high doses or with prolonged use. These effects are mainly mediated through oxidative stress, inflammation, and apoptosis. This study investigates the hepatoprotective potential of royal jelly (RJ), a bee-derived product rich in bioactive compounds, against IBU-induced liver injury in rats. Male Sprague Dawley rats were divided into five groups: i) control, ii) RJ (300 mg/kg), iii) IBU (400 mg/kg), iv) IBU + RJ (150 mg/kg), and v) IBU + RJ (300 mg/kg). All treatments were administered orally for five days. Biochemical, molecular, and histopathological analyses were performed to asssess liver enzyme activities (ALT; alanine aminotransferase, AST; aspartate aminotransferase, ALP; alkaline phosphatase), as well as oxidative stress markers including malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH). The expression of inflammation-related genes (NF-κB; nuclear factor kappa B, TNF-α; tumor necrosis factor alpha, IL-1β; interleukin-1 Beta, TLR4; toll-like receptor 4) was evaluated. Expressions of autophagy markers ( Beclin-1, LC3A; light chain 3A, LC3B; light chain 3B, Atg5; A-autophagy related 5, Atg7; autophagy related 7 ) , apoptotic markers (p53; tumor protein P53, Bax; BCL2 associated X, Bcl-2; B-cell lymphoma 2, Caspase-3, Caspase-9), and Endoplasmic Reticulum (ER) stress indicators (ATF6; activating transcription factor 6, PERK; protein kinase RNA-like endoplasmic reticulum kinase, IRE1; inositol-requiring enzyme 1, CHOP; C/EBP homologous protein, GRP78; glucose-regulated protein 78) were also measured. Additionally, the PI3K/Akt/mTOR ( phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin ) pathway and MMP2/MMP9 (matrix metalloproteinases) were evaluated. IBU significantly increased liver enzymes, lipid peroxidation, and pro-inflammatory and pro-apoptotic signaling while decreasing antioxidant defense and PI3K/Akt/mTOR activity. RJ co-administration markedly ameliorated these alterations, restoring antioxidant levels, reducing inflammation and apoptosis, and improving liver histology. These findings suggest that RJ exhibits significant hepatoprotective properties against NSAID-induced liver injury.

Background: Docetaxel is an anti-microtubule chemotherapeutic agent classified in the taxane group and is widely used in the treatment of many types of cancer.However, systemic toxic effects can be observed in patients treated with docetaxel, and the development of de novo or acquired resistance limits its use and therapeutic efficacy.Thus, investigation of adjuvant treatment approaches has attracted interest.This study aimed to investigate the effects of toyocamycin-mediated inhibition of the Inositol-Requiring Enzyme 1 alpha (IRE1)-X-box Binding Protein 1 (XBP-1) pathway, a physiological mechanism in mammalian cells, on the sensitivity of ovarian cancer cells to docetaxel. Materials and Methods:Human ovarian adenocarcinoma cell lines SKOV3 and Caov-3 were used in the studies.The effects of toyocamycin and docetaxel on cell viability were investigated using the Water-Soluble Tetrazolium-1 assay.The inhibitory effect of toyocamycin on the IRE1-XBP-1 pathway was confirmed by immunoblotting studies.The impact of combined treatment with toyocamycin and docetaxel on migration and invasion was evaluated using wound-healing and Matrigel-coated Boyden chamber invasion assays.The expression levels of some pro-apoptotic and anti-apoptotic genes, such as B-cell lymphoma 2 (BCL2)-associated X apoptosis regulator, BH3-interacting domain death agonist, BCL2 and BCL2-like 1, were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Results:Our results showed that toyocamycin-mediated inhibition of IRE1-XBP-1 signaling significantly suppressed cell viability, migration, and invasion in ovarian cancer cells.In combined treatment with toyocamycin and docetaxel, it was determined that the viability, migration, and invasion were more effectively suppressed in a dose-dependent manner with increasing concentrations of toyocamycin than with either agent alone.Similar results were obtained from qRT-PCR studies.Combination treatments upregulated pro-apoptotic genes and downregulated anti-apoptotic genes in both cell lines. Conclusion:The present data suggest that pharmacological targeting of IRE1/XBP-1 signaling could significantly enhance the sensitivity of ovarian cancer cells to docetaxel.

The antidiabetic drug metformin has potential as an anticancer agent, particularly due to its observed efficacy in breast cancer. Metformin exerts its cytotoxic effects in the induction of endoplasmic reticulum (ER) stress, which can trigger apoptotic cell death pathways. Therefore, the present study aimed to investigate the dose-dependent effects of metformin on ER stress and apoptosis in HER2-positive breast cancer SKBR3 cells. For this purpose, SKBR3 cells were treated with 5, 10 and 20 mM metformin. Cell proliferation was assessed using real-time cell analysis, while expression levels of ER stress-associated genes [glucose-regulated protein 78 kDa (GRP78), PRKR-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6) and CHOP)] were measured by revese transcription-quantitative PCR. Apoptosis was analyzed by Annexin V-FITC/PI flow cytometry in cells treated with 10 and 20 mM metformin. Findings revealed that metformin (5, 10 and 20 mM) dose-dependently inhibited cell proliferation and activated ER stress pathways. Significant increases were observed in gene expression following treatment with 5, 10 and 20 mM metformin, respectively, including GRP78 (3.70-, 5.06- and 7.33-fold; all P<0.0001) PERK (2.48-, 4.36- and 9.11-fold; all P<0.0001), IRE1 (2.15-fold, P=0.001; 2.90-fold, P<0.001; 5.55-fold, P<0.0001), ATF6 (2.43-2.44- and 3.63-fold; all P<0.0001) and particularly in pro-apoptotic CHOP (3.31-, 27.47- and 49.85-fold; all P<0.0001). Flow cytometry revealed that 10 and 20 mM metformin significantly increased early apoptosis to 6.05% (P<0.001) and 7.28% (P<0.001) and late apoptosis to 13.24% (P<0.001) and 20.59% (P<0.001), respectively, compared with controls (early apoptosis, 0.02%; late apoptosis, 0.05%). The present findings demonstrated that metformin activates ER stress response and induces apoptosis in HER2-positive breast cancer cells in a dose-dependent manner. This supports the potential of metformin as an adjuvant therapy, though further in vivo studies are needed to evaluate its clinical applicability.

The endoplasmic reticulum (ER) responds to stimuli that disrupts its homeostasis by activating a signalling network known as unfolded protein response (UPR), that restores cellular balance and determines cell fate through three key sensors: inositol-requiring enzyme 1α (IRE1α), activating transcription factor 6 (ATF6), and protein kinase RNA-like ER kinase (PERK). Emerging evidence suggests that UPR regulates the expression of numerous long non-coding RNAs (lncRNAs), which play critical roles in maintaining ER homeostasis. Here we show that expression of lncRNA H19 is downregulated in response to ER stress in (MCF7, T47D and 293T) cells. Using genetic and pharmacological approaches, we demonstrate that H19 downregulation is primarily mediated by the PERK arm of the UPR. Specifically, knockdown or chemical inhibition of PERK compromised the ER stress-mediated H19 repression, while PERK activation significantly reduced H19 expression. H19 overexpression promotes the optimal activation of ATF6 and PERK pathways, while it attenuates the signalling by IRE1-XBP1 axis of the UPR. Furthermore, in triple-negative breast cancer (TNBC) cells MDA-MB-231, ectopic H19 provided resistance to ER stress-induced apoptosis. Bioinformatic analyses across multiple breast cancer cohorts revealed that high H19 expression was associated with poor prognosis, particularly in basal-like subtypes. Collectively, our findings show that H19 is downregulated during UPR in a PERK-dependent manner, where H19 in turn modulates UPR signalling and cell fate during conditions of ER stress.

Placenta accreta spectrum (PAS) is characterized by abnormal placental adherence/invasion at a scarred implantation bed. Endoplasmic reticulum (ER) stress signaling via inositol-requiring enzyme 1 (IRE1) and protein kinase RNA-like endoplasmic reticulum kinase (PERK) shapes trophoblast behavior, but its interface-specific role in PAS is unclear. We evaluated IRE1 and PERK immunoreactivity in extravillous trophoblast (EVT) subsets to test associations with PAS severity and maternal outcomes. In a retrospective series from a tertiary center, cesarean hysterectomy specimens for PAS and gestational age-matched cesarean controls were analyzed. Immunohistochemistry for IRE1 and PERK was performed on basal plate regions, with semiquantitative immunoreactivity score (IRS:0-12) recorded for EVT subtypes. Associations with clinicopathological parameters and with negative controls were examined with bivariate analyses. IRE1 expression showed no significant associations with clinicopathological parameters. PERK IRS was significantly higher in PAS obstetrical hysterectomy specimens than in controls (mean 9.40±1.96 vs. 4.17±1.52; p<0.001). Across PAS subtypes (accreta/increta/percreta), PERK-IRS varied numerically but not significantly. Within PAS, PERK-IRS was negatively associated with maternal complications (p=0.035). PERK-IRS was elevated at the stressed implantation interface in PAS relative to normal placentation, while IRE1 showed no clear differential signal with the current assay. Paradoxically, within PAS, lower local PERK-IRS signal correlated with complications, suggesting that the magnitude/timing of PERK engagement may influence operative risk. Larger studies incorporating activation-specific markers are warranted to refine biological stratification and prognostication in PAS.