Functional connectivity associated with attention networks differs among subgroups of fibromyalgia patients: an observational case-control study.

Fibromyalgia is a heterogenous chronic pain disorder diagnosed by symptom-based criteria. The aim of this study was to clarify different pathophysiological characteristics between subgroups of patients with fibromyalgia. We identified subgroups with distinct pain thresholds: those with a low pressure pain threshold (PL; 16 patients) and those with a normal pressure pain threshold (PN; 15 patients). Both groups experienced severe pain. We performed resting-state functional MRI analysis and detected 11 functional connectivity pairs among all 164 ROIs with distinct difference between the two groups (p < 0.001). The most distinctive one was that the PN group had significantly higher functional connectivity between the secondary somatosensory area and the dorsal attention network (p < 0.0001). Then, we investigated the transmission pathway of pain stimuli. Functional connectivity of the thalamus to the insular cortex was significantly higher in the PL group (p < 0.01 - 0.05). These results suggest that endogenous pain driven by top-down signals via the dorsal attention network may contribute to pain sensation in a subgroup of fibromyalgia patients with a normal pain threshold. Besides, external pain driven by bottom-up signals via the spinothalamic tract may contribute to pain sensations in another group of patients with a low pain threshold. Trial registration: UMIN000037712.

Unraveling the Connection: Pain and Endoplasmic Reticulum Stress.

Pain is a complex and multifaceted experience. Recent research has increasingly focused on the role of endoplasmic reticulum (ER) stress in the induction and modulation of pain. The ER is an essential organelle for cells and plays a key role in protein folding and calcium dynamics. Various pathological conditions, such as ischemia, hypoxia, toxic substances, and increased protein production, may disturb protein folding, causing an increase in misfolding proteins in the ER. Such an overload of the folding process leads to ER stress and causes the unfolded protein response (UPR), which increases folding capacity in the ER. Uncompensated ER stress impairs intracellular signaling and cell function, resulting in various diseases, such as diabetes and degenerative neurological diseases. ER stress may be a critical universal mechanism underlying human diseases. Pain sensations involve the central as well as peripheral nervous systems. Several preclinical studies indicate that ER stress in the nervous system is enhanced in various painful states, especially in neuropathic pain conditions. The purpose of this narrative review is to uncover the intricate relationship between ER stress and pain, exploring molecular pathways, implications for various pain conditions, and potential therapeutic strategies.

Effects of Intraoperative Opioid Administration on Postoperative Pain and Pain Threshold: A Randomized Controlled Study.

Fentanyl and short-acting remifentanil are often used in combination. We evaluated the effect of intraoperative opioid administration on postoperative pain and pain thresholds when the two drugs were used. Patients who underwent gynecological laparoscopic surgery were randomly assigned into two groups (15 patients each) to receive either sufficient (group A) or minimum (group B) fentanyl (maximum estimated effect site concentration: A: 7.86 ng/mL, B: 1.5 ng/mL). The estimated effect site concentration at the end of surgery was adjusted to the same level (1 ng/mL). Patients in both groups also received continuous intravenous remifentanil during surgery. The primary outcome was the pressure pain threshold, as evaluated by a pressure algometer 3 h postoperatively. The pressure pain threshold at 3 h postoperatively was 51.1% (95% CI: [44.4-57.8]) in group A and 56.6% [49.5-63.6] in group B, assuming a preoperative value of 100% (p = 0.298). There were no significant differences in pressure pain threshold and numeric rating scale scores between the groups after surgery. The pain threshold decreased significantly in both groups at 3 h postoperatively compared to preoperative values, and recovered at 24 h. Co-administration of both opioids caused hyperalgesia regardless of fentanyl dose.

Pharmacological Chaperones Attenuate the Development of Opioid Tolerance.

Opioids are potent analgesics widely used to control acute and chronic pain, but long-term use induces tolerance that reduces their effectiveness. Opioids such as morphine bind to mu opioid receptors (MORs), and several downstream signaling pathways are capable of inducing tolerance. We previously reported that signaling from the endoplasmic reticulum (ER) contributed to the development of morphine tolerance. Accumulation of misfolded proteins in the ER induced the unfolded protein response (UPR) that causes diverse pathological conditions. We examined the effects of pharmacological chaperones that alleviate ER stress on opioid tolerance development by assessing thermal nociception in mice. Pharmacological chaperones such as tauroursodeoxycholic acid and 4-phenylbutyrate suppressed the development of morphine tolerance and restored analgesia. Chaperones alone did not cause analgesia. Although morphine administration induced analgesia when glycogen synthase kinase 3ß (GSK3ß) was in an inactive state due to serine 9 phosphorylation, repeated morphine administration suppressed this phosphorylation event. Co-administration of chaperones maintained the inactive state of GSK3ß. These results suggest that ER stress may facilitate morphine tolerance due to intracellular crosstalk between the UPR and MOR signaling. Pharmacological chaperones may be useful in the management of opioid misuse.

Pathological Aspects of COVID-19 as a Conformational Disease and the Use of Pharmacological Chaperones as a Potential Therapeutic Strategy.

Coronavirus disease 2019 (COVID-19), the seventh human coronavirus infectious disease, was first reported in Wuhan, China, in December 2019, followed by its rapid spread globally (251,059 deaths, on May 5, 2020, by Johns Hopkins University). An early clinical report showed that fever, cough, fatigue, sputum production, and myalgia were initial symptoms, with the development of pneumonia as the disease progressed. Increases in the level of serum liver enzymes, D-dimer, cardiac troponin I, and creatinine have been observed in severely ill patients, indicating that multiple organ failure had occurred in these cases. Lymphopenia and an increase in interleukin-6 (IL-6) were also observed. Although COVID-19 patients are administered glucocorticoid therapy to treat the excessive immune response to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, the efficacy of this form of therapy is unclear. Viremia is observed in severe cases, suggesting that in addition to type II alveolar epithelial cells, many cell types, such as vascular endothelial cells, cardiomyocytes, renal tubular cells, neuronal cells, and lymphocytes, may be damaged. The improvement of survival rates requires elucidation of the mechanism by which cellular damage occurs during viral infection. Cellular therapy, along with organ support systems such as oxygen therapy, artificial ventilation, extra corporeal membrane oxygenation and dialysis, as well as antiviral therapy, are required. Viral replication in infected host cells may perturb protein folding in the endoplasmic reticulum (ER), causing ER stress. Although an adaptive cellular response, i.e. the unfolded protein response, can compensate for the misfolded protein burden to some extent, continued viral proliferation may induce inflammation and cell death. Therefore, we propose that proteostasis dysfunction may cause conformational disorders in COVID-19. The application of pharmacological chaperone therapy to treat COVID-19 patients is additionally discussed.

Conflicting Actions of Inhalational Anesthetics, Neurotoxicity and Neuroprotection, Mediated by the Unfolded Protein Response.

Preclinical studies have shown that exposure of the developing brain to inhalational anesthetics can cause neurotoxicity. However, other studies have claimed that anesthetics can exert neuroprotective effects. We investigated the mechanisms associated with the neurotoxic and neuroprotective effects exerted by inhalational anesthetics. Neuroblastoma cells were exposed to sevoflurane and then cultured in 1% oxygen. We evaluated the expression of proteins related to the unfolded protein response (UPR). Next, we exposed adult mice in which binding immunoglobulin protein (BiP) had been mutated, and wild-type mice, to sevoflurane, and evaluated their cognitive function. We compared our results to those from our previous study in which mice were exposed to sevoflurane at the fetal stage. Pre-exposure to sevoflurane reduced the expression of CHOP in neuroblastoma cells exposed to hypoxia. Anesthetic pre-exposure also significantly improved the cognitive function of adult wild-type mice, but not the mutant mice. In contrast, mice exposed to anesthetics during the fetal stage showed cognitive impairment. Our data indicate that exposure to inhalational anesthetics causes endoplasmic reticulum (ER) stress, and subsequently leads to an adaptive response, the UPR. This response may enhance the capacity of cells to adapt to injuries and improve neuronal function in adult mice, but not in developing mice.

Pathogenic Effects of Impaired Retrieval between the Endoplasmic Reticulum and Golgi Complex.

Cellular activities, such as growth and secretion, are dependent on correct protein folding and intracellular protein transport. Injury, like ischemia, malnutrition, and invasion of toxic substances, affect the folding environment in the endoplasmic reticulum (ER). The ER senses this information, following which cells adapt their response to varied situations through the unfolded protein response. Activation of the KDEL receptor, resulting from the secretion from the ER of chaperones containing the KDEL sequence, plays an important role in this adaptation. The KDEL receptor was initially shown to be necessary for the retention of KDEL sequence-containing proteins in the ER. However, it has become clear that the activated KDEL receptor also regulates bidirectional transport between the ER and the Golgi complex, as well as from the Golgi to the secretory pathway. In addition, it has been suggested that the signal for KDEL receptor activation may also affect several other cellular activities. In this review, we discuss KDEL receptor-mediated bidirectional transport and signaling and describe disease models and human diseases related to KDEL receptor dysfunction.

A simple and safe method for tracheal intubation using a supraglottic intubation-aid device in mice.

Although mice are a commonly used animal species in experimental medicine, airway management of this species is not easy due to their small size. In order to develop a new method of tracheal intubation in mice, we produced a supraglottic intubation-aid conduit (SIAC) for mice, and tested the efficacy of this device in spontaneously breathing mice anesthetized with sevoflurane inhalation. The success rate of tracheal intubation with the crude prototype of the SIAC was 50% and adverse effects on respiration and some trauma in the upper airway were occasionally observed. After refining the size and shape of the SIAC, the success rate of tracheal intubation with the refined prototype of the SIAC was 100% without any serious adverse effects. This study showed that it is possible to produce a supraglottic airway device to aid tracheal intubation in mice and that the shape and size of the SIAC play a crucial role in successful tracheal intubation in mice.

Decreased Protein Quality Control Promotes the Cognitive Dysfunction Associated With Aging and Environmental Insults.

Background: Most neurodegenerative diseases are sporadic and develop with age. Degenerative neural tissues often contain intra- and extracellular protein aggregates, suggesting that the proteostasis network that combats protein misfolding could be dysfunctional in the setting of neurodegenerative disease. Binding immunoglobulin protein (BiP) is an endoplasmic reticulum (ER) chaperone that is crucial for protein folding and modulating the adaptive response in early secretory pathways. The interaction between BiP and unfolded proteins is mediated by the substrate-binding domain and nucleotide-binding domain with ATPase activity. The interaction facilitates protein folding and maturation. BiP has a recovery motif at the carboxyl terminus. The aim of this study is to examine cognitive function in model mice with an impaired proteostasis network by expressing a mutant form of BiP lacking the recovery motif. We also investigated if impairments of cognitive function were exacerbated by exposure to environmental insults, such as inhaled anesthetics. Methods: We examined cognitive function by performing radial maze testing with mutant BiP mice and assessed the additional impact of general anesthesia in the context of proteostasis dysfunction. Testing over 8 days was performed 10 weeks, 6 months, and 1 year after birth. Results: Age-related cognitive decline occurred in both forms of mice. The mutant BiP and anesthetic exposure promoted cognitive dysfunction prior to the senile period. After senescence, when mice were tested at 6 months of age and at 1 year old, there were no significant differences between the two genotypes in terms of the radial maze testing; furthermore, there was no significant difference when tested with and without anesthetic exposure. Conclusion: Our data suggest that aging was the predominant factor underlying the impairment of cognitive function in this study. Impairment of the proteostasis network may promote age-related neurodegeneration, and this is exacerbated by external insults.

The Role of BiP Retrieval by the KDEL Receptor in the Early Secretory Pathway and its Effect on Protein Quality Control and Neurodegeneration.

Protein quality control in the early secretory pathway is a ubiquitous eukaryotic mechanism for adaptation to endoplasmic reticulum (ER) stress. An ER molecular chaperone, immunoglobulin heavy chain-binding protein (BiP), is one of the essential components in this process. BiP interacts with nascent proteins to facilitate their folding. BiP also plays an important role in preventing aggregation of misfolded proteins and regulating the ER stress response when cells suffer various injuries. BiP is a member of the 70-kDa heat shock protein (HSP70) family of molecular chaperones that resides in the ER. Interaction between BiP and unfolded proteins is mediated by a substrate-binding domain and a nucleotide-binding domain for ATPase activity, leading to protein folding and maturation. BiP also possesses a retrieval motif in its carboxyl terminal. When BiP is secreted from the ER, the Lys-Asp-Glu-Leu (KDEL) receptor in the post-ER compartments binds with the carboxyl terminal KDEL sequence of BiP and returns BiP to the ER via coat protein complex I (COPI) vesicular transport. Although yeast studies showed that BiP retrieval by the KDEL receptor is not essential in single cells, it is crucial for multicellular organisms, where some essential proteins require retrieval to facilitate folding and maturation. Experiments in knock-in mice expressing mutant BiP with the retrieval motif deleted revealed a unique role of BiP retrieval by the KDEL receptor in neuronal development and age-related neurodegeneration.

Sublethal endoplasmic reticulum stress caused by the mutation of immunoglobulin heavy chain-binding protein induces the synthesis of a mitochondrial protein, pyrroline-5-carboxylate reductase 1.

Most human neurodegenerative diseases are sporadic and appear later in life. Aging and neurodegeneration are closely associated, and recent investigations reveal that endoplasmic reticulum (ER) stress is involved in the progression of these features. Immunoglobulin heavy chain-binding protein (BiP) is an ER chaperone that is central to ER functions. We produced knock-in mice expressing a mutant BiP that lacked the retrieval sequence to elucidate the effect of a functional defect in an ER chaperone in multicellular organisms. The homozygous mutant BiP mice died within several hours after birth because of respiratory failure with an impaired biosynthesis of pulmonary surfactant by alveolar type II cells. The heterozygous mutant BiP mice grew up to be apparently normal adults, although some of them revealed motor disabilities as they aged. Here, we report that the synthesis of a mitochondrial protein, pyrroline-5-carboxylate reductase 1 (PYCR1), is enhanced in the brains of homozygous mutant BiP mice. We performed a two-dimensional gel analysis followed by liquid chromatography-tandem mass spectrometry. PYCR1 was identified as one of the enhanced proteins. We also found that sublethal ER stress caused by tunicamycin treatment induced the synthesis of PYCR1 in murine fibroblasts. PYCR1 has been shown to be related to the aging process. Mutations in the PYCR1 gene cause cutis laxa with progeroid features and mental retardation. These findings suggest a pathophysiological interaction between ER stress and a mitochondrial function in aging.

Physiological and Biochemical Responses to Continuous Saline Irrigation Inside the Abdominal Cavity in Anesthetized Pigs.

BACKGROUND: Water-filled laparoendoscopic surgery (WaFLES) has been proposed as a novel surgical system achieving a wide surgical field in the intra- and extraperitoneal space with continuous irrigation of isotonic fluid into the field. Despite its technical feasibility and advantages, the safety of the technique, particularly with respect to physiological functions, has not been evaluated. METHODS: Various types of minor abdominal surgeries were performed under general anesthesia in nine adult pigs either by conventional laparoscopy (n = 3) or WaFLES (n = 6). In addition to esophageal temperature and body weight, cardiorespiratory variables such as blood pressure, heart rate, and arterial blood gas parameters were compared before and after the surgeries. Blood samples were obtained for assessing changes in biochemical parameters before and after the surgeries. RESULTS: Three to seven hours of various surgeries were completed without critical cardiorespiratory events in all animals. Oxygenation and ventilation were maintained regardless of the techniques used for the surgeries. A minor increase of body weight (2.5% of initial body weight), metabolic acidosis, hyperkalemia, and impaired hepatic function were observed after WaFLES surgeries. CONCLUSIONS: The preliminary study indicated no serious immediate adverse effects of the WaFLES technique.

Small-Incision Laparoscopy-Assisted Surgery Under Abdominal Cavity Irrigation in a Porcine Model.

BACKGROUND: Laparoscopic and robot-assisted surgeries are performed under carbon dioxide insufflation. Switching from gas to an isotonic irrigant introduces several benefits and avoids some adverse effects of gas insufflation. We developed an irrigating device and apparatus designed for single-incision laparoscopic surgery and tested its advantages and drawbacks during surgery in a porcine model. MATERIALS AND METHODS: Six pigs underwent surgical procedures under general anesthesia. A 30-cm extracorporeal cistern was placed over a 5-6-cm abdominal incision. The abdomen was irrigated with warm saline that was drained via a suction tube placed near the surgical field and continuously recirculated through a closed circuit equipped with a hemodialyzer as a filter. Irrigant samples from two pigs were cultured to check for bacterial and fungal contamination. Body weight was measured before and after surgery in four pigs that had not received treatments affecting hemodynamics or causing diuresis. RESULTS: One-way flow of irrigant ensured laparoscopic vision by rinsing blood from the surgical field. Through a retroperitoneal approach, cystoprostatectomy was successfully performed in three pigs, nephrectomy in two, renal excision in two, and partial nephrectomy in one, under simultaneous ultrasonographic monitoring. Through a transperitoneal approach, liver excision and hemostasis with a bipolar sealing device were performed in three pigs, and bladder pedicle excision was performed in one pig. Bacterial and fungal contamination of the irrigant was observed on the draining side of the circuit, but the filter captured the contaminants. Body weight increased by a median of 2.1% (range, 1.2-4.4%) of initial weight after 3-5 hours of irrigation. CONCLUSIONS: Surgery under irrigation is feasible and practical when performed via a cistern through a small abdominal incision. This method is advantageous, especially in the enabling of continuous and free-angle ultrasound observation of parenchymal organs. Adverse effects of abdominal irrigation need further assessment before use in humans.

Late-onset of spinal neurodegeneration in knock-in mice expressing a mutant BiP.

Most human neurodegenerative diseases are sporadic, and appear later in life. While the underlying mechanisms of the progression of those diseases are still unclear, investigations into the familial forms of comparable diseases suggest that endoplasmic reticulum (ER) stress is involved in the pathogenesis. Binding immunoglobulin protein (BiP) is an ER chaperone that is central to ER function. We produced knock-in mice expressing a mutant BiP that lacked the retrieval sequence in order to evaluate the effect of a functional defect in an ER chaperone in multi-cellular organisms. Here we report that heterozygous mutant BiP mice revealed motor disabilities in aging. We found a degeneration of some motoneurons in the spinal cord accompanied by accumulations of ubiquitinated proteins. The defect in retrieval of BiP by the KDEL receptor leads to impaired activities in quality control and autophagy, suggesting that functional defects in the ER chaperones may contribute to the late onset of neurodegenerative diseases.

The effect of endoplasmic reticulum stress on neurotoxicity caused by inhaled anesthetics.

BACKGROUND: The mechanisms by which inhaled anesthetics cause neurotoxicity are not well clarified. Exposure to inhaled anesthetics induces a release of Ca from the endoplasmic reticulum (ER) into the cytosol. Aberrant Ca mobilization may alter the protein-folding environment in the ER, causing ER stress. Binding immunoglobulin protein (BiP) is an ER chaperone that is critical to ER functions. Because ER stress leads to cellular dysfunction and apoptotic cell death, leading to diverse human disorders such as neurodegenerative diseases, we hypothesized ER stress may play a role in neurotoxicity caused by inhaled anesthetics. METHODS: We investigated the relationship between ER stress and neurodegeneration caused by inhaled anesthetics by using knock-in mice expressing a mutant BiP and neuronal culture cells. Neuronal culture cells and mutant BiP pregnant mice were exposed to 3% sevoflurane. The levels of BiP and C/EBP homologous protein (CHOP), a transcription factor related to cell death during ER stress, were evaluated by Western blot in neuronal cells and fetal brains delivered by cesarean delivery. Cell death in the fetal brains was evaluated with TUNEL staining. Statistical significance was assessed using unpaired t test and analysis of variance followed by multiple comparison tests. RESULTS: Sevoflurane exposure enhanced the expression of BiP and CHOP significantly in neuronal culture cells. A chemical chaperone that assisted ER functions reduced the expression of CHOP induced by sevoflurane exposure. In an in vivo study, we observed that an enhanced expression of CHOP and significantly more apoptotic cells in the brains of homozygous mutant BiP fetuses compared with the wild type. Mouse embryonic fibroblasts derived from the mutant BiP mice also exhibited enhanced levels of CHOP and cleaved caspase-3 after sevoflurane exposure. CONCLUSIONS: Sevoflurane exposure may cause ER stress, which is tolerated to some extent in wild-type cells. When this tolerance is limited, like in cells with mutant BiP, the exposure leads to cell death in the brain, suggesting that ER stress may partially mediate neurotoxicity caused by inhaled anesthetics. This study suggests that patients with certain conditions sensitive to ER stress such as ischemia, hypoxia, developing brain, or neurodegenerative diseases may be vulnerable to inhaled anesthetics.

[Endoplasmic reticulum stress and opioid tolerance withdrawal].

Morphine is a potent analgesic, but its molecular mechanism for tolerance formation is not fully understood. Binding immunoglobulin protein (BiP) is an endoplasmic reticulum (ER) chaperone that is central to ER functions. We examined knock-in mice expressing a mutant BiP with the retrieval sequence deleted in order to elucidate physiological BiP functions. We tested thermal antinociceptive effects of morphine on heterozygous mutant BiP mice by a hot plate test. Repeated morphine administration caused the development of morphine tolerance in the wild-type mice. The activation of glycogen synthase kinase 3beta (GSK3beta) was associated with morphine tolerance, since an inhibitor of GSK3beta prevented it. On the other hand, the mutant BiP mice showed less morphine tolerance, and the activation of GSK3beta was suppressed in their brain. These results suggest that BiP may play an important role in the development of morphine tolerance. Furthermore, we found that a chemical chaperone that improves ER protein folding capacity also attenuated the development of morphine tolerance in wild-type mice, suggesting a possible clinical application of chemical chaperones in preventing morphine tolerance.

Valproate attenuates the development of morphine antinociceptive tolerance.

Morphine is a potent opioid analgesic. Repeated administration of morphine induces tolerance, thus reducing the effectiveness of analgesic treatment. Although some adjuvant analgesics can increase morphine analgesia, the precise molecular mechanism behind their effects remains unclear. Opioids bind to the mu opioid receptor (MOR). Morphine tolerance may be derived from alterations in the intracellular signal transduction after MOR activation. Chronic morphine treatment activates glycogen synthase kinase 3ß (GSK3ß), whose inhibition diminishes morphine tolerance. Valproate is widely prescribed as an anticonvulsant and a mood stabilizer for bipolar disorders because it increases the amount of γ-aminobutyric acid (GABA) in the central nervous system. Although the activation of GABAergic neurons may be responsible for the chief pharmacologic effect of valproate, recent studies have shown that valproate also suppresses GSK3ß activity. We examined the effect of valproate on the development of morphine antinociceptive tolerance in a mouse model of thermal injury. Mice were treated with morphine alone or with morphine and valproate twice daily for 5 days. The resulting antinociceptive effects were assessed using a hot plate test. While mice treated with morphine developed tolerance, co-administration of valproate attenuated the development of tolerance and impaired the activation of GSK3ß in mice brains. Valproate alone did not show analgesic effects; nevertheless, it functioned as an adjuvant analgesic to prevent the development of morphine tolerance. These results suggest that the modulation of GSK3ß activity by valproate may be useful and may play a role in the prevention of morphine tolerance.

BiP, an endoplasmic reticulum chaperone, modulates the development of morphine antinociceptive tolerance.

Morphine is a potent analgesic, but the molecular mechanism for tolerance formation after repeated use is not fully understood. Binding immunoglobulin protein (BiP) is an endoplasmic reticulum (ER) chaperone that is central to ER function. We examined knock-in mice expressing a mutant BiP with the retrieval sequence deleted in order to elucidate physiological processes that are sensitive to BiP functions. We tested the thermal antinociceptive effect of morphine in heterozygous mutant BiP mice in a hot plate test. Paw withdrawal latencies before and after a single administration of morphine were not significantly different between the wild-type and mutant BiP mice. Repeated morphine administration caused the development of morphine tolerance in the wild-type mice. The activation of glycogen synthase kinase 3b (GSK-3b) was associated with morphine tolerance, because an inhibitor of GSK-3ß prevented it. On the other hand, the mutant BiP mice showed less morphine tolerance, and the activation of GSK-3b was suppressed in their brain. These results suggest that BiP may play an important role in the development of morphine tolerance. Furthermore, we found that a chemical chaperone which improves ER protein folding capacity also attenuated the development of morphine tolerance in wild-type mice, suggesting a possible clinical application of chemical chaperones in preventing morphine tolerance.

Dysfunction of the ER chaperone BiP accelerates the renal tubular injury.

Tubular-interstitial injury plays a key role in the progression of chronic kidney disease. Although endoplasmic reticulum (ER) stress plays significant roles in the development of chronic diseases such as neurodegenerative disease, cardiomyopathy and diabetes mellitus, its pathophysiological role in chronic renal tubular cell injury remains unknown. BiP is an essential chaperone molecule that helps with proper protein folding in the ER. Recently, we have produced a knock-in mouse that expresses a mutant-BiP in which the retrieval sequence to the ER is deleted in order to elucidate physiological processes that are sensitive to ER functions in adulthood. The heterozygous mutant-BiP mice showed significant tubular-interstitial lesions with aging. Furthermore, proteinuria induced by chronic protein overload accelerated the tubular-interstitial lesions in the mutant mice, accompanying caspase-12 activation and tubular cell apoptosis. These results suggest that the ER stress pathway is significantly involved in the pathophysiology of chronic renal tubular-interstitial injury in vivo.

Altered quality control in the endoplasmic reticulum causes cortical dysplasia in knock-in mice expressing a mutant BiP.

Binding immunoglobulin protein (BiP) is an endoplasmic reticulum (ER) molecular chaperone that is central to ER function. We examined knock-in mice expressing a mutant BiP in order to elucidate physiological processes that are sensitive to BiP functions during development and adulthood. The mutant BiP lacked the retrieval sequence that normally functions to return BiP to the ER from the secretory pathway. This allowed us to examine the effects of a defect in ER function without completely eliminating BiP function. The homozygous mutant BiP neonates died after birth due to respiratory failure. Besides that, the mutant BiP mice displayed disordered layer formation in the cerebral cortex and cerebellum, a neurological phenotype of reeler mutant-like malformation. Consistent with the phenotype, Cajal-Retzius (CR) cells did not secrete reelin, and the expression of reelin was markedly reduced posttranscriptionally. Furthermore, the reduction in the size of the whole brain and the apparent scattering of CR cells throughout the cortex, which were distinct from the reeler phenotype, were also seen. These findings suggest that the maturation and secretion of reelin in CR cells and other factors related to neural migration may be sensitive to aberrant ER quality control, which may cause various neurological disorders.