Distinct mechanisms of allopregnanolone and diazepam underlie neuronal oscillations and differential antidepressant effect

The rapid relief of depressive symptoms is a major medical requirement for effective treatments for major depressive disorder (MDD). A decrease in neuroactive steroids contributes to the pathophysiological mechanisms associated with the neurological symptoms of MDD. Zuranolone (SAGE-217), a neuroactive steroid that acts as a positive allosteric modulator of synaptic and extrasynaptic δ-subunit-containing GABAA receptors, has shown rapid-onset, clinically effective antidepressant action in patients with MDD or postpartum depression (PPD). Benzodiazepines, on the other hand, act as positive allosteric modulators of synaptic GABAA receptors but are not approved for the treatment of patients with MDD. It remains unclear how differences in molecular mechanisms contribute to the alleviation of depressive symptoms and the regulation of associated neuronal activity. Focusing on the antidepressant-like effects and neuronal activity of the basolateral amygdala (BLA) and medial prefrontal cortex (mPFC), we conducted a head-to-head comparison study of the neuroactive steroid allopregnanolone and the benzodiazepine diazepam using a mouse social defeat stress (SDS) model. Allopregnanolone but not diazepam exhibited antidepressant-like effects in a social interaction test in SDS mice. This antidepressant-like effect of allopregnanolone was abolished in extrasynaptic GABAA receptor δ-subunit knockout mice (δko mice) subjected to the same SDS protocol. Regarding the neurophysiological mechanism associated with these antidepressant-like effects, allopregnanolone but not diazepam increased theta oscillation in the BLA of SDS mice. This increase did not occur in δko mice. Consistent with this, allopregnanolone potentiated tonic inhibition in BLA interneurons via δ-subunit-containing extrasynaptic GABAA receptors. Theta oscillation in the mPFC of SDS mice was also increased by allopregnanolone but not by diazepam. Finally, allopregnanolone but not diazepam increased frontal theta activity in electroencephalography recordings in naïve and SDS mice. Neuronal network alterations associated with MDD showed decreased frontal theta and beta activity in depressed SDS mice. These results demonstrated that, unlike benzodiazepines, neuroactive steroids increased theta oscillation in the BLA and mPFC through the activation of δ-subunit-containing GABAA receptors, and this change was associated with antidepressant-like effects in the SDS model. Our findings support the notion that the distinctive mechanism of neuroactive steroids may contribute to the rapid antidepressant effects in MDD.

Efficacy of ensitrelvir against SARS-CoV-2 in a delayed-treatment mouse model

Objectives

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the aetiological agent of coronavirus disease 2019 (COVID-19) and a devastating worldwide health concern. Development of safe and effective treatments is not only important for interventions during the current pandemic, but also for providing general treatment options moving forward. We have developed ensitrelvir, an antiviral compound that targets the 3C-like protease of SARS-CoV-2. In this study, a delayed-treatment mouse model was used to clarify the potential in vivo efficacy of ensitrelvir.

Methods

Female BALB/cAJcl mice of different ages were infected with the SARS-CoV-2 gamma strain (hCoV-19/Japan/TY7-501/2021) or mouse-adapted SARS-CoV-2 MA-P10 and then 24 h post-infection orally administered various doses of ensitrelvir or vehicle. Viral titres and RNA levels in the lungs were quantified using VeroE6/TMPRSS2 cells and RT–qPCR, respectively. Body weight loss, survival, lung weight, cytokine/chemokine production, nucleocapsid protein expression and lung pathology were evaluated to investigate the in vivo efficacy of ensitrelvir.

Results

Based on infectious viral titres and viral RNA levels in the lungs of infected mice, ensitrelvir reduced viral loads in a dose-dependent manner. The antiviral efficacy correlated with increased survival, reduced body weight loss, reduced pulmonary lesions and suppression of inflammatory cytokine/chemokine levels.

Conclusions

This was the first evaluation of the in vivo anti-SARS-CoV-2 efficacy of ensitrelvir in a delayed-treatment mouse model. In this model, ensitrelvir demonstrated high antiviral potential and suppressed lung inflammation and lethality caused by SARS-CoV-2 infection. The findings support the continued clinical development of ensitrelvir as an antiviral agent to treat patients with COVID-19.

Selective Involvement of a Subset of Spinal Dorsal Horn Neurons Operated by a Prodynorphin Promoter in Aβ Fiber-Mediated Neuropathic Allodynia-Like Behavioral Responses in Rats

Mechanical allodynia (pain produced by innocuous stimuli such as touch) is the main symptom of neuropathic pain. Its underlying mechanism remains to be elucidated, but peripheral nerve injury (PNI)-induced malfunction of neuronal circuits in the central nervous system, including the spinal dorsal horn (SDH), is thought to be involved in touch-pain conversion. Here, we found that intra-SDH injection of adeno-associated viral vectors including a prodynorphin promoter (AAV-PdynP) captured a subset of neurons that were mainly located in the superficial laminae, including lamina I, and exhibited mostly inhibitory characteristics. Using transgenic rats that enable optogenetic stimulation of touch-sensing Aβ fibers, we found that the light-evoked paw withdrawal behavior and aversive responses after PNI were attenuated by selective ablation of AAV-PdynP-captured SDH neurons. Notably, the ablation had no effect on withdrawal behavior from von Frey filaments. Furthermore, Aβ fiber stimulation did not excite AAV-PdynP⁺ SDH neurons under normal conditions, but after PNI, this induced excitation, possibly due to enhanced Aβ fiber-evoked excitatory synaptic inputs and elevated resting membrane potentials of these neurons. Moreover, the chemogenetic silencing of AAV-PdynP⁺ neurons of PNI rats attenuated the Aβ fiber-evoked paw withdrawal behavior and c-FOS expression in superficial SDH neurons. Our findings suggest that PNI renders AAV-PdynP-captured neurons excitable to Aβ fiber stimulation, which selectively contributes to the conversion of Aβ fiber-mediated touch signal to nociceptive. Thus, reducing the excitability of AAV-PdynP-captured neurons may be a new option for the treatment of neuropathic allodynia.

Physical disuse contributes to widespread chronic mechanical hyperalgesia, tactile allodynia, and cold allodynia through neurogenic inflammation and spino-parabrachio-amygdaloid pathway activation

Physical disuse could lead to a state of chronic pain typified by complex regional pain syndrome type I due to fear of pain through movement (kinesiophobia) or inappropriate resting procedures. However, the mechanisms by which physical disuse is associated with acute/chronic pain and other pathological signs remain unresolved. We have previously reported that inflammatory signs, contractures, disuse muscle atrophy, spontaneous pain-like behaviors, and chronic widespread mechanical hyperalgesia based on central plasticity occurred after 2 weeks of cast immobilization in chronic post-cast pain (CPCP) rat model. In this study, we also demonstrated dystrophy-like changes, both peripheral nociceptive signals and activation of the central pain pathway in CPCP rats. This was done by the following methods: (1) vascular permeability (Evans blue dye) and inflammatory- and oxidative stress-related messenger RNA changes (real-time quantitative polymerase chain reaction); (2) immunofluorescence of pERK and/or c-Fos expression in the spino-parabrachio-amygdaloid pathway; and (3) blockade of nociceptive-related signals using sciatic nerve block. Furthermore, we demonstrated tactile allodynia using an optogenetic method in a transgenic rat line (W-TChR2V4), cold allodynia using the acetone test, and activation of dorsal horn neurons in the chronic phase associated with chronic mechanical hyperalgesia using c-Fos immunofluorescence. In addition, we showed that nociceptive signals in the acute phase are involved in chronic pathological pain-like behaviors by studying the effects of sciatic nerve block. Thus, we conclude that physical disuse contributes to dystrophy-like changes, spontaneous pain-like behavior, and chronic widespread pathological pain-like behaviors in CPCP rats after 2 weeks of cast immobilization.

Bone marrow-derived cells in the population of spinal microglia after peripheral nerve injury

Accumulating evidence indicates that peripheral nerve injury (PNI) activates spinal microglia that are necessary for neuropathic pain. Recent studies using bone marrow (BM) chimeric mice have reported that after PNI, circulating BM-derived cells infiltrate into the spinal cord and differentiate into microglia-like cells. This raises the possibility that the population of spinal microglia after PNI may be heterogeneous. However, the infiltration of BM cells in the spinal cord remains controversial because of experimental adverse effects of strong irradiation used for generating BM chimeric mice. In this study, we evaluated the PNI-induced spinal infiltration of BM-derived cells not only by irradiation-induced myeloablation with various conditioning regimens, but also by parabiosis and mice with genetically labelled microglia, models without irradiation and BM transplantation. Results obtained from these independent approaches provide compelling evidence indicating little contribution of circulating BM-derived cells to the population of spinal microglia after PNI.

Abstract P6-05-14: Prognostic significance of Ki-67 index value at primary breast tumor in recurrent breast cancer

Introduction: The Ki-67 index value is a prognostic factor in primary breast cancer and is a proliferation marker that also distinguishes between luminal type A and type B breast cancer. Moreover, change in Ki-67 index value due to treatment and recurrence is considered to be important in treating breast cancer. The evaluative procedure in this study was on two levels; first, we examined whether the baseline Ki-67 value at the primary tumor is useful as a prognostic factor after recurrence, and second, we looked at the changes in the values after recurrence.

Patients and Methods: Immunohistochemical (IHC) analysis of the Ki-67 index was performed on 4701 patients with primary breast cancer from 1987 until March 2013 at Kumamoto City Hospital. Out of these patients, there were 666 consecutive cases with recurrence after primary surgery. The fraction of proliferating cells (positive for Ki-67) was based on a count of at least 500 tumor cells in the area including the hot spot, and the Ki-67 values were divided into 2 or 3 groups; <20% and ≥20% (and ≥50%). Items examined were ER, PgR, HER2, tumor size, nodal status at primary tumor, and recurrent site (soft tissue, bone and viscera) and disease-free interval (DFI). Cox's proportional hazard model was used to perform a univariate and multivariate analyses of the factors related to overall survival (OS) after recurrence. The median follow-up period was 65.9 months in the remaining survival group. In 101 recurrent cases from whom the recurrent lesion was resected, the change in biological markers (Ki-67, ER and PgR) were evaluated.

Results: The median Ki-67 value at baseline was 20% in all the cases and 27% in the recurrent cases. In terms of recurrent site, the values were low (23%) in patients with bone metastasis, whereas patients with liver or brain metastasis showed higher values (38% and 53%, respectively). Moreover, DFI was inversely correlated with Ki-67 values. Univariate and multivariate analyses were performed to identify the prognostic factors for OS after recurrence. The significant factors included tumor size, lymph node status, ER, PgR, DFI, recurrent site, and the Ki-67 index value. Among these factors, a multivariate analysis revealed that the Ki-67 index value at primary tumor was an independent significant factor. The hormone receptor positive rate from the primary tumor to recurrence decreased from 67.3% to 63.4% and 64.4% to 50% for ER and PgR, respectively. The Ki-67 index value increased significantly from a mean of 28.9% at primary tumor to 35.7% at relapse. Furthermore, the Ki-67 index value at primary tumor was a significant prognostic factor for OS after recurrence in this cohort.

Conclusion: The Ki-67 value at primary tumor was a significant prognostic factor for OS after recurrence. The Ki-67 index value increased significantly after recurrence. It is therefore important to take the Ki-67 index into consideration in the treatment and follow-up of breast cancer patients.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-05-14.

Abstract P5-05-06: Menopausal status: An important consideration in determining the biology and prognosis of estrogen receptor-positive and progesterone receptor-negative breast cancer

Background: Transcription of the progesterone receptor (PgR) gene is regulated by estrogen in the breast tissue. PgR loss is considered to be a result in the reduction of estrogen receptor (ER) activity, due to either low circulating estrogen in some older women or a high growth factor signaling. Among the ER-positive breast cancer patients, PR-negative cases frequently have a higher resistance to endocrine therapy, and have a poorer prognosis. Therefore, we examined the clinical significance of ER+/PgR- tumors in luminal/HER2 negative breast cancer and its relationship to menopausal status.

Methods: The sample for this study came from 1791 consecutive patients with HER2 negative primary breast cancer from January 2002 to March 2013. The ER and PgR expressions were evaluated using immunohistochemistry (IHC). 1586cases had ER+/PgR+ tumor, 205cases had ER+/PgR- tumor. The items examined were nuclear grade, Ki-67 index value, TP53, tumor size and number of lymph node involvement. The Ki-67 index value and TP53 were evaluated using IHC and the cut-off values were 20% and 50%, respectively. Recurrence free survival (RFS) and breast cancer-specific survival (BCSS) was calculated using the Kaplan-Meier method and evaluated by the log-rank test or generalized Wicoxon test in stage 1 and 2 breast cancer.

Results: In terms of the distribution of ER and PgR status, ER+/PgR- were frequently seen in postmenopausal patients (13.7% vs 6.8%, respectively). Patients with ER+/PgR-and HER2 negative tumors had significantly smaller tumors, lower Ki-67 values, and a lower nuclear grade in the postmenopausal group compared with those in the premenopausal group. Moreover, RFS trended to be better in the postmenopausal group (p = 0.06), but there was no significant difference. BCSS was significantly higher in the postmenopausal cases (p = 0.001). On the other hand, in patients with ER+/PgR+ tumors, there was no significant difference in RFS and BCSS between the post- and pre-menopausal groups.

Conclusion: The ER+/PgR- tumors were more commonly seen in postmenopausal patients. The biological characteristics of ER+/PgR- tumors were significantly different in terms of the Ki-67 index value, nuclear grade, and the prognosis (BCSS and RFS) between pre- and postmenopausal status. Moreover, the postmenopausal group had a more favorable biology and prognosis than the premenopausal group. Therefore, the findings in this study indicate that menopausal status is related to the biology and prognosis in patients with ER+/PgR- tumors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-05-06.

Abstract P1-02-01: Pre-analytical setting is critical for an assessment of the Ki-67 labeling index for breast cancer

Background: The Ki-67 labeling index (LI) is useful in determining the efficacy of chemotherapy for patients with ER-positive and HER2-negative breast cancer. However, standardization of Ki-67 assessment has not yet been established. In terms of the factors that may affect Ki-67 LI, recent studies have focused on inter-observer variability in the interpretation of these values and insufficient attention has been given to the importance of handling the tissue. Therefore, this study focused on the effect of tissue fixation on Ki-67 LI.

Methods:

The effects of several pre-analytical conditions on the Ki-67 LI were studied as follows;

(1) Type of fixation: Each 173 surgically excised tumors were fixed with either 10% neutral buffered formalin or 15% formalin on the same condition, followed by assessment of Ki-67 LI.

(2) Time of fixation: Each study was repeated more than three times to confirm the result.

A: Time to fixation: A part of tumor, sliced from the surgically excised tumor, was kept in 4° for several hours to overnight before formalin fixation. Ki-67 LI was compared between the tumor with immediate and delayed fixation.

B: Time of fixation:

Insufficient fixation: A part of tumor, sliced from the surgically excised tumor, was fixed with formalin for 3 hours, followed by preparation of a paraffin-embedded block. Ki-67 LI was compared between the tumor with proper and shorter fixation.

Prolonged fixation: Some pieces of slice were prepared from the surgically excised tumor, followed by each preparation of a paraffin-embedded block at a designated fixation period. Ki-67 LI was compared among each sample fixed in a different period of time.

(3) Surgically excised tumors on Ki-67 LI:

A: Effect of cutting onto the tumor before fixation: Ki-67 LI in each 595 surgically excised tumor with or without cutting onto the tumor before fixation, was analyzed.

B: Comparison between core needle biopsy and surgically excised tissue: Ki-67 LI in each 136 pairs of core needle biopsy and surgically excised tissue originated from the same tumor was compared.

Results:

(1) Ki-67 LI was significantly higher when 10% neutral buffered formalin was used as a fixative compared to 15% formalin (p = 0.018).

(2) Ki-67 LI was reduced in some degree when time to fixation was delayed, while insufficient fixation caused dramatic reduction of Ki-67 LI compared to that seen in an either ER or HER2. A prolonged period of fixation caused gradual reduction of Ki-67 LI associated with diminished nuclear labeling.

(3) Ki-67 LI was significantly higher in the tumor cut onto before fixation (p = 0.018). There was no significant difference in Ki-67 LI between core needle and surgically excised specimens (p = 0.107), when the tumor was properly fixed.

Conclusion: Our results suggest that pre-analytical setting critically influences the Ki-67 labeling. In order to standardize Ki-67 LI assessment in breast cancer, the care in handling of the pre-analytical tissue is crucial in determining accurate Ki-67 values.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-02-01.

Abstract PD06-07: Evaluation of an optimal cut-off point for the Ki-67 index as a prognostic factor in primary breast cancer

Background: The proliferation biomarker Ki-67 is considered to be a prognostic factor for breast cancer and has been investigated in several studies. However, there is no standard cut-off point for the Ki-67 index. Therefore, we retrospectively investigated an optimal cut-off point in terms of the prognostic factor in primary breast cancer.

Patients&Methods: Immunohistochemical (IHC) analysis of the proliferation marker Ki-67 index was performed on 4338 patients with primary breast cancer until March 2012 at Kumamoto City Hospital. Out of these patients, there were 2375 consecutive cases with ER and/or PgR positive and HER2 negative tumors since 1997. Items examined were ER, PgR, HER2, tumor size, nodal status, nuclear grade, and p53 overexpression. The Kaplan-Meier test was used to calculate prognosis (cumulative disease-free survival (DFS) and overall survival (OS)) and tested with the log-rank procedure. Cox's proportional hazard model was used to perform a univariate and multivariate analyses of the factors related to DFS. In addition, an analysis was conducted to determine various cut-off values for the Ki-67 index.

Results: The median Ki-67 value was 21%, with a mean of 26.2%. Univariate and multivariate analysis revealed that the Ki-67 index was an independent prognostic factor for DFS and OS. A multivariate analysis revealed the following hazard ratio (HR) and cut-off values for the Ki-67 index; HR was 1.92 in cases with a cut-off value of 20%, 1.91 in 35%, 1.87 in 40%, 1.89 in 45% and 1.79 in 50%, respectively. These findings suggested that the optimal cut-off point was 20%. In the cases with luminal type (ER and/or PgR positive and HER2 negative) breast cancer, a higher Ki-67 value (20% ≤) correlated with larger tumor size, positive nodes, higher grade, and overexpression of p53. Moreover, patients with a higher Ki-67 value showed significantly lower DFS/OS rates. A multivariate analysis also revealed that the Ki-67 index is a significant prognostic factor in luminal type breast cancer.

Conclusion: The optimal cut-off value for the Ki-67 index is 20%. Moreover, this proliferation marker is a significant prognostic factor in evaluating primary breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD06-07.

Survival after locoregional recurrence in patients after breast cancer surgery

141

Background: The purpose of this study was to investigate factors for survival after locoregional recurrence in patients who underwent mastectomy or breast-conserving therapy (BCT) for primary breast cancer in our hospital.

Methods: Out of 3,332 patients operated on from 1989 to 2008, 50 patients had chest wall recurrences after mastectomy (CWR), 40 patients had regional nodal recurrences (RNR), and 24 patients had ipsilateral breast tumor recurrences (IBTR) from 1997 to 2008. To investigate the prognostic factors for survival after locoregional recurrence, we conducted uni- and multivariate analyses of these cases.

Results: The median follow-up time was 49.2 months. The 5-year survivals after recurrence of the patients with CWR, RNR and IBRT were 52%, 28%, and 68%, respectively. And the 10-year survivals were 15%, 0%, and 62%, respectively. Furthermore, the 5-year distant metastasis-free survivals were 24%, 13%, and 59%, respectively. In a multivariate analysis of the patients with CWR, type of recurrent nodules (diffuse/single, RR 21.0, p= 0.001), pT (T3 or 4 /T1, RR 11.4, p=0.01), pN (N3/N0, RR 15.5, p= 0.03), Ki67 of primary tumor (>50%/<20%, RR6.7, p=0.02) and ER of the primary tumor (+ / -, RR 2.6, p = 0.02) were independent prognostic factors. In a multivariate analysis of RNR, the method of first line salvage therapy (local /local + systemic, RR 16.1, p = 0.01) was only an independent prognostic factor. In the cases of IBTR, there were no independent prognostic factors for survival after recurrence.

Conclusions: Although CWR developed distant metastases within 5 years, the survival depended upon the several biological factors. RNR developed distant metastases within a few years and provided poor prognosis. These suggested that RNR would be the first appearance of systemic metastasis not local disease. In contrast, IBTR provided better prognosis and a salvage treatment cured about 60% of the patients.

An evaluation of changes in biological markers (ER, PgR, or Ki67) after neoadjuvant chemotherapy (ET: epirubicin and docetaxel) in operable breast cancer

10613

Background: Neoadjuvant chemotherapy (NAC) is a valid option not only for advanced breast cancer but also for operable breast cancer. It was reported that disease-free and overall survival after NAC were equivalent to those after adjuvant therapy. The role of biological markers for the prediction of NAC may be evaluated using pathological responsiveness. In this study, we investigated the changes in biological markers such as estrogen receptor (ER), progesterone receptor (PgR), or Ki67 after NAC. Methods: Eligible patients (pts) were newly diagnosed with large primary tumors > 3 cm or positive nodes. Fifty-two pts were enrolled and received epirubicin 60 mg/m2 followed by docetaxel 60 mg/m2 every 3 weeks for 4 cycles before surgery. In 51 cases out of the pts, pre-treatment needle biopsies and surgical specimen were analyzed for expression of ER, PgR, Her-2/neu, p53 and Ki67 by immunohistochemistry, and these data were compared to the pathological response. The pathological response was evaluated using the criteria of Japan Breast Cancer Society. Results: The median age was 47 (range, 29–67) and the mean tumor size was 5.2cm (range, 1.5–14.5). The clinical response was 86%; the BCS rate was 73% and pathological response was 31% including 3 cases with pCR. Regarding changes in biology after NAC, an average rate of ER positive cells significantly fell in 37% from 47% and that of PgR positive cells also fell in 14% from 32%. Most of cases, whose tumors were changed to ER/PgR negative from ER/PgR positive, were premenopausal women accompanied with amenorrhea during the treatment. Patients with lower ER, PgR, or a higher proliferation had a significantly greater benefit from NAC. The overexpression of Her2 was not correlated to pathological response, while p53 staining had a predictive value. And patients with positive nodes had a significantly favorable disease-free survival. Conclusions: The clinical effect of NAC (ET regimen) and the BCS rate by NAC were high. Although the rates of ER and PgR positive cells and proliferation were significantly reduced by NAC, a lower ER, PgR, or a higher proliferation might reflect a good pathological response. A negative change of ER or PgR by NAC might correlate with amenorrhea in premenopausal pts.

No significant financial relationships to disclose.

Development of gastric emptying in the human fetus

OBJECTIVE

To evaluate stomach size and the development of gastric emptying in human fetuses using ultrasound.

DESIGN

Clinical observational study.

METHODS

The motility and peristalsis of the fetal stomach were studied in 80 normal fetuses between 12 and 39 weeks of gestation. Fetal gastric motility was assessed by analysis of videotaped recordings of ultrasound images of the stomach taken in real time.

RESULTS

Fetal maximum gastric area gradually increased and minimum gastric areas gradually decreased after 20 weeks of gestation. At term, the maximum and minimum gastric area ratios were approximately 13 and 5%, respectively. The change in fetal gastric area, defined as the difference of maximum and minimum gastric area ratios, was relatively constant at 3% from 12 to 15 weeks of gestation to 20-23 weeks of gestation. It increased significantly (to 8%) after 24-27 weeks of gestation until term.

CONCLUSIONS

Fetal gastric emptying was quantified and its development assessed during pregnancy. A critical point of gastric development, associated with an increase in the change of gastric volume, was identified at 24-25 weeks of gestation.