The Role of Adjuvant Therapy Following Surgical Resection of Small Cell Lung Cancer: A Multi-Center Study / Journal of the Korean Cancer Association, 대한암학회지

Purpose@#This multi-center, retrospective study was conducted to evaluate the long-term survival in patients who underwent surgical resection for small cell lung cancer (SCLC) and to identify the benefit of adjuvant therapy following surgery. @*Materials and Methods@#The data of 213 patients who underwent surgical resection for SCLC at four institutions were retrospectively reviewed. Patients who received neoadjuvant therapy or an incomplete resection were excluded. @*Results@#The mean patient age was 65.29±8.93 years, and 184 patients (86.4%) were male. Lobectomies and pneumonectomies were performed in 173 patients (81.2%), and 198 (93%) underwent systematic mediastinal lymph node dissections. Overall, 170 patients (79.8%) underwent adjuvant chemotherapy, 42 (19.7%) underwent radiotherapy to the mediastinum, and 23 (10.8%) underwent prophylactic cranial irradiation. The median follow-up period was 31.08 months (interquartile range, 13.79 to 64.52 months). The 5-year overall survival (OS) and disease-free survival were 53.4% and 46.9%, respectively. The 5-year OS significantly improved after adjuvant chemotherapy in all patients (57.4% vs. 40.3%, p=0.007), and the survival benefit of adjuvant chemotherapy was significant in patients with negative node pathology (70.8% vs. 39.7%, p=0.004). Adjuvant radiotherapy did not affect the 5-year OS (54.6% vs. 48.5%, p=0.458). Age (hazard ratio [HR], 1.032; p=0.017), node metastasis (HR, 2.190; p < 0.001), and adjuvant chemotherapy (HR, 0.558; p=0.019) were associated with OS. @*Conclusion@#Adjuvant chemotherapy after surgical resection in patients with SCLC improved the OS, though adjuvant radiotherapy to the mediastinum did not improve the survival or decrease the locoregional recurrence rate.

Predicting Postoperative Complications and Long-Term Survival After Lung Cancer Surgery Using Eurolung Risk Score

Background@#This study aimed to assess the clinical relevance of the parsimonious Eurolung risk scoring system for predicting postoperative morbidity, mortality, and long-term survival in Korean patients with surgically resected non-small cell lung cancer. @*Methods@#This retrospective analysis used the data of patients who underwent anatomical resection for non-small cell lung cancer between 2004 and 2018 at a single institution. The parsimonious aggregate Eurolung score was calculated for each patient. The Cox regression model was used to determine the ability of the Eurolung scoring system for predicting longterm outcomes. @*Results@#Of the 7,278 patients in the study, cardiopulmonary complications and mortality occurred in 687 (9.4%) and 53 (0.7%) patients, respectively. The rate of cardiopulmonary complications and mortality gradually increased with the increase in the Eurolung risk scores (all P < 0.001). When risk scores were grouped into four categories, the Eurolung scoring system showed a stepwise deterioration of overall survival with the increase in risk scores, and this association was statistically significant (P < 0.001). Multivariate Cox analysis showed that the Eurolung scoring system, classified into four categories, was a significant prognostic factor of overall survival even after adjusting for covariates such as tumor histology and pathological stage (P < 0.001). @*Conclusion@#Stratification based on the parsimonious Eurolung scoring system showed good discriminatory ability for predicting postoperative morbidity, mortality, and long-term survival in South Korean patients with surgically resected non-small cell lung cancer. This might help clinicians to provide a detailed prognosis and decide the appropriate treatment option for high-risk patients with non-small cell lung cancer.

Natural Progression of Ground-glass Nodules after Curative Resection for Non-small Cell Lung Cancer

Background@#This retrospective study investigated the natural course of synchronous groundglass nodules (GGNs) that remained after curative resection for non-small-cell lung cancer (NSCLC). @*Methods@#Prospectively collected retrospective data were reviewed concerning 2,276 patients who underwent curative resection for NSCLC between 2008 and 2017. High-resolution computed tomography or thin-section computed tomography data of 82 patients were included in the study. Growth in size was considered the most valuable outcome, and patients were grouped according to GGN size change. Patient demographic data (e.g., age, sex, and smoking history), perioperative data (e.g., GGN characteristics, histopathology and pathological stage of the resected tumours), and other medical history were evaluated in a risk factor analysis concerning GGN size change. @*Results@#The median duration of follow-up was 36.0 months (interquartile range, 23.0–59.3 months). GGN size decreased in 6 patients (7.3%), was stationary in 43 patients (52.4%), and increased in 33 patients (40.2%). In univariate analysis, male sex, the GGN size on initial CT, part-solid GGN and smoking history (≥ 10 pack-years) were significant risk factors. Among them, multivariate analysis revealed that lager GGN size, part-solid GGN and smoking history were independent risk factors. @*Conclusion@#During follow-up, 40.2% of GGNs increased in size, emphasising that patients with larger GGNs, part-solid GGN or with a smoking history should be observed.

Experience of International Air Transportation and Subsequent Lung Transplant in a Patient with COVID-19-associated Acute Respiratory Distress Syndrome: a Case Report

We report an inspiring case of a 55-year-old Korean female diagnosed with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS) in Mexico.The patient was assessed for lung transplant as a salvage therapy for treatment-refractory ARDS following no signs of clinical improvement for > 7 weeks, despite best treatment.The patient was transported from Mexico to Korea by air ambulance under venovenous extracorporeal membrane oxygenation (ECMO) support. She was successfully bridged to lung transplant on day 88, 49 days after the initiation of ECMO support. ECMO was successfully weaned at the end of operation, and no bleeding or primary graft dysfunction was observed within the first 72 hours. The patient was liberated from mechanical ventilation on postoperative day 9 and transferred to the general ward 5 days later. Despite the high doses of immunosuppressants, there was no evidence of viral reactivation after transplant.At 3 months post-transplantation, she was discharged to home without complication. Our experience suggests that successful lung transplant for COVID-19-associated ARDS is feasible even in a patient with prolonged pre-transplant ECMO support. Lung transplant may be considered a salvage therapy for COVID-19-associated ARDS that does not respond to conventional treatments.

Experience of International Air Transportation and Subsequent Lung Transplant in a Patient with COVID-19-associated Acute Respiratory Distress Syndrome: a Case Report

We report an inspiring case of a 55-year-old Korean female diagnosed with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS) in Mexico.The patient was assessed for lung transplant as a salvage therapy for treatment-refractory ARDS following no signs of clinical improvement for > 7 weeks, despite best treatment.The patient was transported from Mexico to Korea by air ambulance under venovenous extracorporeal membrane oxygenation (ECMO) support. She was successfully bridged to lung transplant on day 88, 49 days after the initiation of ECMO support. ECMO was successfully weaned at the end of operation, and no bleeding or primary graft dysfunction was observed within the first 72 hours. The patient was liberated from mechanical ventilation on postoperative day 9 and transferred to the general ward 5 days later. Despite the high doses of immunosuppressants, there was no evidence of viral reactivation after transplant.At 3 months post-transplantation, she was discharged to home without complication. Our experience suggests that successful lung transplant for COVID-19-associated ARDS is feasible even in a patient with prolonged pre-transplant ECMO support. Lung transplant may be considered a salvage therapy for COVID-19-associated ARDS that does not respond to conventional treatments.

Infections in Lung Transplant Recipients during and after Prophylaxis

Background@#The timeline of infections after lung transplantation has been changed with the introduction of new immunosuppressants and prophylaxis strategies. The study aimed to investigate the epidemiological characteristics of infectious diseases after lung transplantation in the current era. @*Materials and Methods@#All patients who underwent lung or heart–lung transplantation at our institution between October 29, 2008 and April 3, 2019 were enrolled. We retrospectively reviewed the patients' medical records till April 2, 2020. @*Results@#In total, 100 consecutive lung transplant recipients were enrolled. The median follow-up period was 28 months after lung transplantation. A total of 127 post–lung transplantation bacterial infections occurred. Catheter-related bloodstream infection (25/84, 29.8%) was the most common within 6 months and pneumonia (23/43, 53.5%) was the most common after 6 months. Most episodes (35/40, 87.5%) of respiratory viral infections occurred after 6 months, mainly as upper respiratory infections. The remaining episodes (5/40, 12.5%) mostly manifested as lower respiratory tract infections. Seventy cytomegalovirus infections observed in 43 patients were divided into 23 episodes occurring before and 47 episodes occurring after discontinuing prophylaxis. Of 10 episodes of cytomegalovirus disease, four occurred during prophylaxis and six occurred after prophylaxis.Of 23 episodes of post–lung transplantation fungal infection, 7 were aspergillosis and all occurred after the discontinuation of prophylaxis. @*Conclusion@#Lung transplant recipients experienced a high burden of infection even after 6 months, especially after the end of the prophylaxis period. Therefore, these patients should be continued to be monitored long-term for infectious disease.

Infections in Lung Transplant Recipients during and after Prophylaxis

Background@#The timeline of infections after lung transplantation has been changed with the introduction of new immunosuppressants and prophylaxis strategies. The study aimed to investigate the epidemiological characteristics of infectious diseases after lung transplantation in the current era. @*Materials and Methods@#All patients who underwent lung or heart–lung transplantation at our institution between October 29, 2008 and April 3, 2019 were enrolled. We retrospectively reviewed the patients' medical records till April 2, 2020. @*Results@#In total, 100 consecutive lung transplant recipients were enrolled. The median follow-up period was 28 months after lung transplantation. A total of 127 post–lung transplantation bacterial infections occurred. Catheter-related bloodstream infection (25/84, 29.8%) was the most common within 6 months and pneumonia (23/43, 53.5%) was the most common after 6 months. Most episodes (35/40, 87.5%) of respiratory viral infections occurred after 6 months, mainly as upper respiratory infections. The remaining episodes (5/40, 12.5%) mostly manifested as lower respiratory tract infections. Seventy cytomegalovirus infections observed in 43 patients were divided into 23 episodes occurring before and 47 episodes occurring after discontinuing prophylaxis. Of 10 episodes of cytomegalovirus disease, four occurred during prophylaxis and six occurred after prophylaxis.Of 23 episodes of post–lung transplantation fungal infection, 7 were aspergillosis and all occurred after the discontinuation of prophylaxis. @*Conclusion@#Lung transplant recipients experienced a high burden of infection even after 6 months, especially after the end of the prophylaxis period. Therefore, these patients should be continued to be monitored long-term for infectious disease.

Long-Term Outcomes of Adult Lung Transplantation Recipients: A Single-Center Experience in South Korea / 결핵

BACKGROUND: Recently, the number of lung transplants in South Korea has increased. However, the long-term outcome data is limited. In this study, we aimed to investigate the long-term outcomes of adult lung transplantation recipients. METHODS: Among the patients that underwent lung transplantation at a tertiary referral center in South Korea between 2008 and 2017, adults patient who underwent deceased-donor lung transplantation with available follow-up data were enrolled. Their medical records were retrospectively reviewed. RESULTS: Through eligibility screening, we identified 60 adult patients that underwent lung (n=51) or heart-lung transplantation (n=9) during the observation period. Idiopathic pulmonary fibrosis (46.7%, 28/60) was the most frequent cause of lung transplantation. For all the 60 patients, the median follow-up duration for post-transplantation was 2.6 years (range, 0.01–7.6). During the post-transplantation follow-up period, 19 patients (31.7%) died at a median duration of 194 days. The survival rates were 75.5%, 67.6%, and 61.8% at 1 year, 3 years, and 5 years, respectively. Out of the 60 patients, 8 (13.3%) were diagnosed with chronic lung allograft dysfunction (CLAD), after a mean duration of 3.3±2.8 years post-transplantation. The CLAD development rate was 0%, 17.7%, and 25.8% at 1 year, 3 years, and 5 years, respectively. The most common newly developed post-transplantation comorbidity was the chronic kidney disease (CKD; 54.0%), followed by diabetes mellitus (25.9%). CONCLUSION: Among the adult lung transplantation recipients at a South Korea tertiary referral center, the long-term survival rates were favorable. The proportion of patients who developed CLAD was not substantial. CKD was the most common post-transplantation comorbidity.

Recent Trends in Demographics, Surgery, and Prognosis of Patients with Surgically Resected Lung Cancer in a Single Institution from Korea

BACKGROUND: Over the past few decades, demographics information has changed significantly in patients with surgically resected lung cancer. Herein, we evaluated the recent trends in demographics, surgery, and prognosis of lung cancer surgery in Korea. METHODS: Patients with surgically resected primary lung cancer from 2002 to 2016 were retrospectively analyzed. Multivariable Cox regression analysis was conducted to identify prognostic factors for overall survival. The annual percent change (APC) and statistical significance were calculated using the Joinpoint software. RESULTS: A total of 7,495 patients were enrolled. Over the study period, the number of lung cancer surgeries continued to increase (P < 0.05). The proportion of women to total subjects has also increased (P < 0.05). The proportion of elderly patients (≥ 70 years) as well as those with tumors measuring 1–2 cm and 2–3 cm significantly increased in both genders (all P < 0.05). The proportion of patients with adenocarcinoma, video-assisted thoracic surgery, sublobar resection, and pathological stage I significantly increased (P < 0.05). The 5-year overall survival rate of lung cancer surgery increased from 61.1% in 2002–2006 to 72.1% in 2012–2016 (P < 0.001). The operative period was a significant prognostic factor in multivariable Cox analysis (P < 0.001). CONCLUSION: The mean age of patients with lung cancer surgery increased gradually, whereas tumor size reduced. Prognosis of lung cancer surgery improved with recent increases in the frequency of adenocarcinoma, video-assisted thoracic surgery, sublobar resection, and pathological stage I. The operation period itself was also an independent prognostic factor for overall survival.

Long-Term Outcomes of Adult Lung Transplantation Recipients: A Single-Center Experience in South Korea / 결핵및호흡기질환

BACKGROUND@#Recently, the number of lung transplants in South Korea has increased. However, the long-term outcome data is limited. In this study, we aimed to investigate the long-term outcomes of adult lung transplantation recipients.@*METHODS@#Among the patients that underwent lung transplantation at a tertiary referral center in South Korea between 2008 and 2017, adults patient who underwent deceased-donor lung transplantation with available follow-up data were enrolled. Their medical records were retrospectively reviewed.@*RESULTS@#Through eligibility screening, we identified 60 adult patients that underwent lung (n=51) or heart-lung transplantation (n=9) during the observation period. Idiopathic pulmonary fibrosis (46.7%, 28/60) was the most frequent cause of lung transplantation. For all the 60 patients, the median follow-up duration for post-transplantation was 2.6 years (range, 0.01–7.6). During the post-transplantation follow-up period, 19 patients (31.7%) died at a median duration of 194 days. The survival rates were 75.5%, 67.6%, and 61.8% at 1 year, 3 years, and 5 years, respectively. Out of the 60 patients, 8 (13.3%) were diagnosed with chronic lung allograft dysfunction (CLAD), after a mean duration of 3.3±2.8 years post-transplantation. The CLAD development rate was 0%, 17.7%, and 25.8% at 1 year, 3 years, and 5 years, respectively. The most common newly developed post-transplantation comorbidity was the chronic kidney disease (CKD; 54.0%), followed by diabetes mellitus (25.9%).@*CONCLUSION@#Among the adult lung transplantation recipients at a South Korea tertiary referral center, the long-term survival rates were favorable. The proportion of patients who developed CLAD was not substantial. CKD was the most common post-transplantation comorbidity.

Surgical Outcomes of Radiographically Noninvasive Lung Adenocarcinoma according to Surgical Strategy: Wedge Resection, Segmentectomy, and Lobectomy

BACKGROUND: The aim of this study was to evaluate the outcomes of surgical resection in patients with radiographically noninvasive lung adenocarcinoma according to the surgical strategy. METHODS: A retrospective study was conducted of 128 patients who underwent pulmonary resection for ground-glass opacity (GGO)–dominant nodules measuring ≤2 cm with a consolidation/tumor ratio ≤0.25 based on computed tomography between 2008 and 2015. The 5-year disease-free survival (DFS) rate and 5-year overall survival (OS) rate were analyzed. RESULTS: Among the 128 patients, wedge resection, segmentectomy, and lobectomy were performed in 40 (31.2%), 22 (17.2%), and 66 patients (51.6%), respectively. No significant differences were found among the groups in the mean size of tumors (p=0.119), the rate of pure-GGO nodules (p=0.814), the consolidation/tumor ratio (p=0.695), or the rate of invasive adenocarcinoma (p=0.378). Centrally located tumors were more common in the lobectomy group (21.2%) than in the wedge resection (0%) or segmentectomy (0%) groups (p=0.001). There were no significant differences in the 5-year DFS rate (100%, 100%, 92.7%, respectively; p=0.76) or 5-year OS rate (100%, 100%, 100%; p=0.223) among the wedge resection, segmentectomy, and lobectomy groups. CONCLUSION: For radiographically noninvasive lung adenocarcinoma measuring ≤2 cm with a consolidation/tumor ratio ≤0.25, wedge resection and segmentectomy could be comparable surgical options to lobectomy.

Surgical Options for Malignant Mesothelioma: A Single-Center Experience

BACKGROUND: We investigated the surgical outcomes of patients who underwent therapeutic surgery for malignant pleural mesothelioma (MPM) at a single center. METHODS: A retrospective review of 21 patients who underwent therapeutic surgery for MPM from January 2001 to June 2015 was conducted to assess their outcomes. The patients' characteristics and postoperative course, including complications, mortality, overall survival, and recurrence-free survival, were analyzed. RESULTS: Of the 21 patients who underwent therapeutic surgery, 15 (71.4%) underwent extrapleural pneumonectomy, 2 pleurectomy (9.5%), and 4 excision (19.1 %). The median age was 57 years (range, 32–79 years) and 15 were men (71.4%). The mean hospital stay was 16 days (range, 1–63 days). Median survival was 14.3 months. The survival rate was 54.2%, 35.6%, and 21.3% at 1, 3, and 5 years, respectively. In patients' postoperative course, heart failure was a major complication, occurring in 3 patients (14.3%). The in-hospital mortality rate was 2 of 21 (9.5%) due to a case of severe pneumonia and a case of acute heart failure. CONCLUSION: A fair 5-year survival rate of 21.3% was observed after surgical treatment. Heart failure was a major complication in our cohort. Various surgical methods can be utilized with MPM, each with its own benefits, taking into consideration the severity of the disease and the comorbidities of the patient. Patients with local recurrence may be candidates for surgical intervention, with possible satisfying results.

The First Living-Donor Lobar Lung Transplantation in Korea: a Case Report

Lung transplantation is the only treatment for end-stage lung disease, but the problem of donor shortage is unresolved issue. Herein, we report the first case of living-donor lobar lung transplantation (LDLLT) in Korea. A 19-year-old woman patient with idiopathic pulmonary artery hypertension received her father's right lower lobe and her mother's left lower lobe after pneumonectomy of both lungs in 2017. The patient has recovered well and is enjoying normal social activity. We think that LDLLT could be an alternative approach to deceased donor lung transplantation to overcome the shortage of lung donors.

Intravenous Anesthetic, Propofol Affects Synaptic Responses in Cerebellar Purkinje Cells

OBJECTIVE: Propofol is an intravenously administered anesthetic that enhances γ-aminobutyric acid-mediated inhibition in the central nerve system. Other mechanisms may also be involved in general anesthesia. Propofol has been implicated in movement disorders. The cerebellum is important for motor coordination and motor learning. The aim of the present study was to investigate the propofol effect on excitatory synaptic transmissions in cerebellar cortex. METHODS: Excitatory postsynaptic currents by parallel fiber stimulation and complex spikes by climbing fiber stimulation were monitored in Purkinje cells of Wister rat cerebellar slice using whole-cell patch-clamp techniques. RESULTS: Decay time, rise time and amplitude of excitatory postsynaptic currents at parallel fiber Purkinje cell synapses and area of complex spikes at climbing fiber Purkinje cell synapses were significantly increased by propofol administration. CONCLUSION: The detected changes of glutamatergic synaptic transmission in cerebellar Purkinje cell, which determine cerebellar motor output, could explain cerebellar mechanism of motor deficits induced by propofol.

Clinical Outcomes of Lung Transplantation: Experience at Asan Medical Center

BACKGROUND@#Lung transplantation is a life-saving procedure in patients with end-stage lung disease, and is increasingly performed in Korea.@*METHODS@#We retrospectively evaluated the outcomes of patients who received a lung transplant at Asan Medical Center between January 2008 and December 2016. Thirteen of 54 patients experienced multiorgan transplantation; the remaining 41 who received only lung grafts were included.@*RESULTS@#The mean age of the lung transplant recipients was 44.6 years; 27 were men and 14 were women. The most frequent reasons were idiopathic interstitial pneumonia (21 of 41 patients, 51.2%), interstitial lung disease (9 of 41, 22.0%), and bronchiolitis obliterans after bone marrow transplantation (7 of 41, 17.1%). The median waiting time was 47 days, and many patients received preoperative intensive care (27 of 41, 65.9%), ventilator support (26 of 41, 63.4%), or extracorporeal life support (19 of 41, 46.3%). All 41 patients received bilateral lung grafts. Ten deaths occurred (24.3%), including 5 cases of early mortality (12.2%) and 5 cases of late mortality (12.2%). The 1-, 3-, and 5-year survival rates were 78.9%, 74.2%, and 69.3%, respectively.@*CONCLUSION@#Despite a high percentage of patients who required preoperative intensive care, the transplantation outcomes were acceptable.

Clinical Outcomes of Lung Transplantation: Experience at Asan Medical Center / 대한흉부외과학회지

BACKGROUND: Lung transplantation is a life-saving procedure in patients with end-stage lung disease, and is increasingly performed in Korea. METHODS: We retrospectively evaluated the outcomes of patients who received a lung transplant at Asan Medical Center between January 2008 and December 2016. Thirteen of 54 patients experienced multiorgan transplantation; the remaining 41 who received only lung grafts were included. RESULTS: The mean age of the lung transplant recipients was 44.6 years; 27 were men and 14 were women. The most frequent reasons were idiopathic interstitial pneumonia (21 of 41 patients, 51.2%), interstitial lung disease (9 of 41, 22.0%), and bronchiolitis obliterans after bone marrow transplantation (7 of 41, 17.1%). The median waiting time was 47 days, and many patients received preoperative intensive care (27 of 41, 65.9%), ventilator support (26 of 41, 63.4%), or extracorporeal life support (19 of 41, 46.3%). All 41 patients received bilateral lung grafts. Ten deaths occurred (24.3%), including 5 cases of early mortality (12.2%) and 5 cases of late mortality (12.2%). The 1-, 3-, and 5-year survival rates were 78.9%, 74.2%, and 69.3%, respectively. CONCLUSION: Despite a high percentage of patients who required preoperative intensive care, the transplantation outcomes were acceptable.

Case of mucinous adenocarcinoma of the lung associated with congenital pulmonary airway malformation in a neonate / 소아과

Congenital pulmonary airway malformation (CPAM), previously known as congenital cystic adenomatoid malformation, is a rare developmental lung abnormality associated with rhabdomyosarcoma, pleuropulmonary blastoma, and mucinous adenocarcinoma of the lung. We report an unusual case of a 10-day-old male newborn with a left lower lobe pulmonary cyst who underwent lobectomy, which revealed type II CPAM complicated by multifocal mucinous adenocarcinoma. KRAS sequencing revealed a somatic mutation in Codon12 (GGT → GAT), suggesting the development of a mucinous adenocarcinoma in the background of mucinous metaplasia. Mucinous adenocarcinoma is the most common lung tumor associated with CPAM, but it generally occurs in older children and adults. Further, all cases in the literature are of type I CPAM. This case in a neonate indicates that malignant transformation can occur very early in type II CPAM.

Hydrogen peroxide inhibits Ca²⁺ efflux through plasma membrane Ca²⁺-ATPase in mouse parotid acinar cells

Intracellular Ca²⁺ mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide (H₂O₂) on cytosolic Ca²⁺ accumulation in mouse parotid acinar cells. Intracellular Ca²⁺ levels were slowly elevated when 1 mM H₂O₂ was perfused in the presence of normal extracellular Ca²⁺. In a Ca²⁺-free medium, 1 mM H₂O₂ still enhanced the intracellular Ca²⁺ level. Ca²⁺ entry tested using manganese quenching technique was not affected by perfusion of 1 mM H₂O₂. On the other hand, 10 mM H₂O₂ induced more rapid Ca²⁺ accumulation and facilitated Ca²⁺ entry from extracellular fluid. Ca²⁺ refill into intracellular Ca²⁺ store and inositol 1,4,5-trisphosphate (1 µM)-induced Ca²⁺ release from Ca²⁺ store was not affected by 1 mM H₂O₂ in permeabilized cells. Ca²⁺ efflux through plasma membrane Ca²⁺-ATPase (PMCA) was markedly blocked by 1 mM H₂O₂ in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected H₂O₂-induced Ca²⁺ accumulation through PMCA inactivation. From the above results, we suggest that excessive production of H₂O₂ under pathological conditions may lead to cytosolic Ca²⁺ accumulation and that the primary mechanism of H₂O₂-induced Ca²⁺ accumulation is likely to inhibit Ca²⁺ efflux through PMCA rather than mobilize Ca²⁺ ions from extracellular medium or intracellular stores in mouse parotid acinar cells.

Hydrogen peroxide attenuates refilling of intracellular calcium store in mouse pancreatic acinar cells

Intracellular calcium (Ca²⁺) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide (H₂O₂) on intracellular Ca²⁺ accumulation in mouse pancreatic acinar cells. Perfusion of H₂O₂ at 300 µM resulted in additional elevation of intracellular Ca²⁺ levels and termination of oscillatory Ca²⁺ signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca²⁺. Antioxidants, catalase or DTT, completely prevented H₂O₂-induced additional Ca²⁺ increase and termination of Ca²⁺ oscillation. In Ca²⁺-free medium, H₂O₂ still enhanced CCh-induced intracellular Ca²⁺ levels and thapsigargin (TG) mimicked H₂O₂-induced cytosolic Ca²⁺ increase. Furthermore, H₂O₂-induced elevation of intracellular Ca²⁺ levels was abolished under sarco/endoplasmic reticulum Ca²⁺ ATPase-inactivated condition by TG pretreatment with CCh. H₂O₂ at 300 µM failed to affect store-operated Ca²⁺ entry or Ca²⁺ extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca²⁺ uniporter blocker, failed to attenuate H₂O₂-induced intracellular Ca²⁺ elevation. These results provide evidence that excessive generation of H₂O₂ in pathological conditions could accumulate intracellular Ca²⁺ by attenuating refilling of internal Ca²⁺ stores rather than by inhibiting Ca²⁺ extrusion to extracellular fluid or enhancing Ca²⁺ mobilization from extracellular medium in mouse pancreatic acinar cells.

Chronic Ca²⁺ influx through voltage-dependent Ca²⁺ channels enhance delayed rectifier K⁺ currents via activating Src family tyrosine kinase in rat hippocampal neurons

Excessive influx and the subsequent rapid cytosolic elevation of Ca²⁺ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic Ca²⁺ level in normal as well as pathological conditions. Delayed rectifier K⁺ channels (I(DR) channels) play a role to suppress membrane excitability by inducing K⁺ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under Ca²⁺-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of IDR channels to hyperexcitable conditions induced by high Ca²⁺ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high Ca²⁺-treatment significantly increased the amplitude of IDR without changes of gating kinetics. Nimodipine but not APV blocked Ca²⁺-induced IDR enhancement, confirming that the change of I(DR) might be targeted by Ca²⁺ influx through voltage-dependent Ca²⁺ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated I(DR) enhancement was not affected by either Ca²⁺-induced Ca²⁺ release (CICR) or small conductance Ca²⁺-activated K⁺ channels (SK channels). Furthermore, PP2 but not H89 completely abolished I(DR) enhancement under high Ca²⁺ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for Ca²⁺-mediated I(DR) enhancement. Thus, SFKs may be sensitive to excessive Ca²⁺ influx through VDCCs and enhance I(DR) to activate a neuroprotective mechanism against Ca²⁺-mediated hyperexcitability in neurons.