Endergonic addition of N-methylamines to aromatic ketones driven by photochemical offset of the entropic cost

Intermolecular addition reactions are generally accompanied by an entropic penalty due to the decrease of molecular numbers during the reaction, which sometimes makes the reaction endergonic. Here we demonstrate that such an endergonic reaction can be promoted with light-energy as a driving force; N-methylamines were added to aromatic ketones to produce aminoalcohols under UV-light irradiation. The reaction represents an obvious example showing that the photochemical approach is effective to offset such an entropic cost, and thereby to drive thermodynamically uphill addition reactions. Moreover the present reactions are highly expedient from the synthetic view point, being transition-metal-catalyst-free, scalable, highly atom economical, and regioselective. The product amines can be converted in one step to functional multi-arylated enamines, which are potentially valuable compounds in electronic materials.

Abstract P4-08-19: Progression-free survival or time to progression in comparative clinical trials of metastatic breast cancer as a potential surrogate for overall survival: A systematic review of 49 trials focusing on breast cancer subtype

Background: Overall survival (OS) is the established endpoint to evaluate the effects of drug treatment in comparative clinical trials of metastatic breast cancer. But assessing OS requires long follow-up periods and large sample size, which raise costs and create long delays in the drug approval process. Progression-free survival (PFS) or time to progression (TTP) is considered as a surrogate for OS and is often used as an alternative to OS. In some cancers the two endpoints are highly correlated, but in others they are not. Furthermore, the effect of breast cancer (BC) subtypes on the surrogacy of PFS/TTP for OS has not been completely defined.

Method: A systematic literature review of randomized control trials was conducted to identify studies that reported both the hazard ratio (HR) of PFS/TTP and OS for BC subtypes {i.e. estrogen receptor (ER) positive, HER2 positive, and triple negative (TN)}. The correlation between the HR of PFS/TTP and OS was evaluated using weighted Spearman's rank correlation.

Results: A total of 49 trials (34 phase III trials and 15 phase II trials) were selected for analysis. Among these trials, there were 8 comparison trials between one chemotherapy and another chemotherapy regimen, 18 comparison trials between chemotherapy and chemotherapy plus molecularly-targeted therapy, 9 comparison trials between one endocrine therapy and another endocrine therapy, and 5 comparison trials between endocrine therapy and endocrine therapy plus molecularly-targeted therapy. There were 17 trials reporting the HR of PFS/TTP and OS for ER positive, 16 trials for HER2 positive, and 9 trials for TN BC. Weighted Spearman's rank correlation revealed that coefficient between the HR of PFS/TTP and OS was 0.721(p<.0001) for all trials, 0.873(p< .0001) for ER positive, 0.642(p=0.0055) for HER2 positive, and 0.615(p=0.078)for TN BC.

Conclusion: There was a strong correlation between the HR of PFS/TTP and OS for ER positive BC, and a weak correlation between the HR of PFS/TTP and OS for HER2 positive and TN BC. The validity of using PFS/TTP as an OS surrogate marker was shown for metastatic BC, especially for ER positive BC.

Citation Format: Tsukioki T, Taira N, Sakamaki K, Suzuki Y, Kajiwara Y, Hatono M, Takahashi Y, Kawata K, Kochi M, Iwamoto T, Ikeda H, Shien T, Doihara H. Progression-free survival or time to progression in comparative clinical trials of metastatic breast cancer as a potential surrogate for overall survival: A systematic review of 49 trials focusing on breast cancer subtype [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-19.

Abstract P2-05-06: Effects of a soy isoflavone in breast cancer treatment

Background : Isoflavones are phytoestrogens that may be effective in preventing osteoporosis, reducing cardiovascular events, and improving menopausal symptoms such as hot flash due to their estrogen-like actions. Isoflavones are currently used as a supplement for improving symptoms of menopause. Epidemiological studies have shown that ingestion of soy products may also reduce the risk of breast cancer, and antitumor effects on hormone receptor (HR)-positive breast cancer cells have been shown in vitro for equol, an isoflavone metabolite. Equol binds to estrogen receptors (ERα, β) and is thought to antagonize ERα-estradiol binding in the presence of estradiol. Since equol shows an antiestrogenic effect, similar to that of the hormonal agent tamoxifen, it is thought that equol acts as a selective estrogen receptor modulator (SERM), but the mechanism is still unclear. In this study, we evaluated the antitumor effects of equol alone and in combination with existing therapeutic agents in HR-positive breast cancer cells, and examined the mechanism of these effects.

Methods : The antitumor effects of equol alone and in combination with hormone drugs (4-hydroxytamoxifen (Tam), fulvestrant (Ful)) and chemotherapeutic agents (paclitaxel (Ptx), doxorubicin (Dox)) were examined using a MTS assay. Combination indexes (CIs) were determined in HR-positive MCF-7, T-47D, and ZR-75-1 cell lines. The mechanisms of the drug effects were evaluated by Western blot for assessment of changes in chemoresistance factors at the protein level.

Results : In MCF-7, T-47D and ZR-75-1 cells, there was a concentration-dependent antitumor effect of equol and of the other hormonal agents. CIs showed an antagonistic effect of equol with Tam and a synergistic effect with Ful in all cell lines. Equol also had an antagonistic effect with the two chemotherapeutic agents, with the strongest antagonism occurring at a low dose of equol. Western blot showed that ER, PgR, Cyclin D1 and Bcl-2 were upregulated via ER at a low concentration of equol, similarly to the effect of 17-β-estradiol (E2), and ER, PgR, Cyclin D1 and Bcl-2 were downregulated at a high concentration, similarly to the effect of Tam. In addition, ER, PgR and cyclin D1 were downregulated with the combination of equol and Tam, while the expression of Bcl-2, a chemoresistance factor, increased.

Conclusion : These results suggest that equol has a concentration-dependent antitumor effect in HR-positive breast cancer cell lines and may antagonize the effect of existing therapeutic agents (hormone drugs and chemotherapeutic agents). In particular, it was considered that in combination of equol and Tam, the apoptosis inducing action of each drug was attenuated and antagonistic effect was shown.

Citation Format: Hatono M, Ikeda H, Taira N, Suzuki Y, Kajiwara Y, Kawata K, Takahashi Y, Tsukioki T, Kochi M, Iwamoto T, Shien T, Doihara H. Effects of a soy isoflavone in breast cancer treatment [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-05-06.

Abstract P4-13-09: Sequential second line endocrine therapy is still an effective strategy for postmenopausal ER+ and HER2- advanced breast cancer with low sensitivity to initial endocrine therapy

Background:It is unclear how to define responsiveness to endocrine therapy (ET) during the clinical course of advanced breast cancer (ABC), especially in evaluation of the effect of sequential ET. Objective:The goal of the study was to evaluate the efficacy of second line treatment of physician's choice (2nd-line TPC) for estrogen receptor-positive (ER+) and HER2-negative postmenopausal ABC with very low or low sensitivity to initial ET. Methods:A multicenter prospective observational cohort study was performed for 2nd-line TPCs. ABC with low sensitivity to initial ET was defined as recurrence within 5 years (yrs) during adjuvant ET or progression within 9 months (mo.) of initial ET. Similarly, ABC with very low sensitivity to initial ET was defined as recurrence within 2 yrs during adjuvant ET or progression within 3 mo. of initial ET. The expected clinical benefit rate (CBR: defined as patients who achieved CR, PR or SD for 24 weeks) was 50%. The null hypothesis of a CBR of 30% was tested with a one-sided α of 5%. 90% confidence intervals (CIs) were calculated for hypothesis tests. Results: A total of 56 patients (pts) were enrolled, but 7 were ineligible and one discontinued before starting the protocol treatment. The median age was 66 yrs (range: 41-88) and the median BMI was 23.4 kg/m2 (16.4-31.9). All pts were ER+ and 80% were PgR+. Most of pts had a baseline PS of 0 or 1, 90% had invasive ductal carcinoma, and 10% had invasive lobular carcinoma. Postoperative recurrence was detected in 84% and these pts had a median duration of adjuvant ET of 30.5 mo. (5.3-58.9). De novo stage IV ABC was present in 16%, with a median duration of first-line ET of 5 mo. (2.3-10.8). Adjuvant chemotherapy including anthracycline- and/or a taxane-containing regimen was administered in 58% (29/49). As adjuvant ET before initial recurrence, 34 pts received non-steroidal aromatase inhibitors (AIs) (88.0%), 1 received a steroidal AI (2.3%), and 3 received a selective estrogen receptor modulator (SERM). As first line ET in de novo stage IV, 7 pts (14%) were treated with AIs or a SERM (1 case). 2nd-line TPCs were also used, with 40 pts receiving fulvestrant (82%), 5 receiving SERMs (10%), 3 receiving a mTOR inhibitor plus a steroidal AI (6%), and one patient receiving an AI alone. The overall CBR was 44.9% (90% CI: 34.6-57.6, p=0.009), and CBR was similar across following subgroups (PgR+: n=39, 51.3%, 90% CI: 39.6-65.2, p=0.0016; very low sensitivity group: n=17, 58.8%, 90% CI: 42.0-78.8, p=0.003; non-visceral metastases: n=25, 40%, 90% CI; 34.1-65.9, p=0.0175). However, there were not statistically significant CBR in PgR- (n=10, 20.0%, 90% CI; 8.73-50.7, p=0.617), fulvestrant subgroup (n=40, 40.0 %, 90% CI; 29.2-54.2, p=0.063), low sensitive group (n=32, 37.5%, 90% CI; 26.0-53.6, p=0.1326), and visceral metastases (n=24, 48%, 90%CI; 28.2-60.3 p=0.072). The median PFS was 7.1 mo. (95% CI: 5.6-10.6). Conclusion:This study shows that 2nd line ETs was effective and might be a valid option in the sequence of treatments for postmenopausal women with ABC with low sensitivity to initial ET. It was suggested that PgR and visceral metastasis were significant predictive factors for CBR.

Citation Format: Araki K, Fujisawa T, Sakamaki K, Kikawa Y, Iwamoto T, Sangai T, Shien T, Takao S, Nishimura R, Takahashi M, Aihara T, Mukai H, Taira N. Sequential second line endocrine therapy is still an effective strategy for postmenopausal ER+ and HER2- advanced breast cancer with low sensitivity to initial endocrine therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-13-09.

Abstract P2-08-31: Predictive and prognostic value of stromal tumor-infiltrating lymphocytes before and after neoadjuvant therapy in triple negative and HER2-positive breast cancer

Background: Lymphocyte predominant breast cancer subgroup, defined as ≥ 50% stromal tumor-infiltrating lymphocytes (sTILs), is associated with high pathological complete response (pCR) rate after neoadjuvant therapy (NAT) and favorable outcome. In a cohort of triple negative (TNBC) and HER2+ breast cancer (BC) patients treated with NAT, we aimed to assess the predictive and prognostic value of pre- and post-NAT sTILs and the information provided by the change in sTILs during NAT.

Materials and methods: Two-hundred and nine consecutive patients (n=80 TNBC; and n=129 HER2+) who received NAT between 2001 and 2009 in our institution were evaluated. Pre-NAT sTILs were assessed on biopsy sample (baseline) and post-NAT sTILs on surgical specimens just for non-pCR patients. sTILs level was categorized as low 0-9%, intermediate 10-49%, and high ≥50%. The change in sTILs during NAT was calculated as the absolute difference between pre- and post-NAT sTILs. We evaluated the association of pre-NAT sTILs and pCR, and the association between pre- and post-NAT sTILs, and their change with relapse-free survival (RFS).

Results: Overall pCR rate was 37.8% (31.3% for TNBC, 41.2% for ER+/HER2+BC, 42.3% for ER-/HER2+BC). In each subtype, pre-NAT low sTILs group was significantly associated with lower pCR rate. During the median follow-up period of 98 months, 44 recurrences (21.1%) were observed. For TNBC, low pre-NAT sTILs group was associated with higher recurrence risk compared with int/high sTILs (HR=4.675 [2.013-10.859], p<0.001). For only non-pCR patients, both pre- and post-NAT sTILs were significantly associated with RFS. The risk of recurrence was higher in the group with low pre-NAT sTILs (HR=5.333 [1.731-16.427], p=0.004), and the group of low post-NAT sTILs (HR=4.271 [1.498-12.173], p=0.007). Patients with the change of sTILs increase during NAT were not associated with RFS, compared with decrease or equal group (log-rank p=0.163). In multivariate analysis including both pre- and post-NAT sTILs, only pre-NAT sTILs retained significance (HR=3.844 [1.190-12.421], p=0.024). Low post-NAT sTILs group showed only a borderline significant association with shorter RFS (HR=2.836 [0.951-8.457], p=0.061), but it suggests that both pre- and post-NAT sTILs might provide independent prognostic information. In ER+/HER2+BC, low pre-NAT sTILs were associated with short RFS (p=0.036), but this association was not significant when only non-pCR patients were considered. In ER−/HER2+BC, sTILs were not significantly associated with RFS.

Conclusion: In TN and HER2+ BCs, tumors with low pre-NAT sTILs have a low likelihood to achieve a pCR (predictive marker). In TNBC, low pre-NAT sTILs were associated with higher recurrence risk. In non-pCR TNBC patients, both low pre- and post-NAT sTILs were associated with shorter RFS. These results suggest that sTILs information should be taken into account when additional post-surgery treatments are considered in non-pCR patients.

Citation Format: Ochi T, Giampaolo B, Murai M, Nozaki F, Kobayashi D, Iwamoto T, Niikura N, Suzuki K, Yamauchi H, Hayashi N. Predictive and prognostic value of stromal tumor-infiltrating lymphocytes before and after neoadjuvant therapy in triple negative and HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-31.

GENOMICS AND LOCAL ADAPTATION OF MYCOBACTERIUM AVIUM

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Iron-catalysed enantioselective Suzuki–Miyaura coupling of racemic alkyl bromides

The first iron-catalyzed enantioselective Suzuki–Miyaura coupling reaction has been established by using electron-deficient P-chiral bisphosphine ligand (R,R)-QuinoxP*.

[Dysfunction of Na+/Ca2+ exchangers is associated with cognitive decline in Alzheimer's disease]

Na⁺/Ca²⁺ exchanger (NCX) is mainly expressed in the plasma membrane and mediates electrogenical exchange of one Ca²⁺ for three Na⁺, depending on the electrochemical gradients across the plasma membrane. NCX has three different isoforms (NCX1, NCX2, NCX3) encoded by distinct genes in mammals. Here, we report that NCX2 and NCX3 protein levels are relatively reduced in hippocampal CA1 of Alzheimer's disease model mice. Likewise, NCX2^+/- or NCX3^+/- mice exhibited impaired hippocampal LTP and memory-related behaviors. In immunoblot analyses, calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation significantly decreased in hippocampal CA1 of NCX2^+/- mice compared to wild-type mice. By contrast, NCX2^+/- mice was correlated with elevated calcineurin (CaN) activity and rescued by treatment with the calcineurin inhibitor FK506. Taken together, the imbalance of CaMKII and CaN activities with concomitant LTP impairment likely accounts for the learning disability observed in NCX2^+/- mice.

Aberrant Amygdala-Dependent Cued Fear Memory in Na+/Ca2+ Exchanger 1 Heterozygous Mice

Na⁺/Ca²⁺ exchangers (NCXs) are mainly expressed in the plasma membrane and exchange one Ca²⁺ for three Na⁺, depending on the electrochemical gradients across the plasma membrane. NCXs have three isoforms, NCX1-3, encoded by distinct genes in mammals. Here, we report that heterozygous mice lacking NCX1 (NCX1^+/-) exhibit impaired amygdala-dependent cued fear memory. NCX1^+/- mice showed significant impairment in fear-related behaviors measured with the elevated-plus maze, light-dark, open-field, and marble-burying tasks. In addition, NCX1^+/- mice showed abnormality in cued fear memory but not in contextual fear memory in a fear-conditioning task. In immunohistochemical analyses, NCX1^+/- mice had significantly increased number of c-Fos-positive cells in the lateral amygdala (LA) but not in the central amygdala following fear-related tone stimuli. c-Fos expression peaked at 1 h. In concordance with the aberrant fear-related behaviors in NCX1^+/- mice, enhanced long-term potentiation was also observed in the LA of these mice. Furthermore, enhancement of CaMKII or CaMKIV activity in the LA was observed in NCX1^+/- mice by immunoblot analyses. In contrast, CaMKII^+/- but not CaMKIV^-/- mice insufficiently exhibited tone-induced cued fear memory and there was no increase in the number of c-Fos-positive cells in the LA. Altogether, the increased CaMKII activity and consequent c-Fos expression likely account for the dysregulation of amygdala-dependent cued fear memory in NCX1^+/- mice.

Revisiting the definition of estrogen receptor positivity in HER2-negative primary breast cancer

Background

Although 1% has been used as cut-off for estrogen receptor (ER) positivity, several studies have reported that tumors with ER < 1% have characteristics similar to those with 1% ≤ ER < 10%. We hypothesized that in patients with human epidermal growth factor 2 (HER2)-negative breast cancer, a cut-off of 10% is more useful than one of 1% in discriminating for both a better pathological complete response (pCR) rate to neoadjuvant chemotherapy and a better long-term outcome with adjuvant hormonal therapy. Our objectives were to identify a percentage of ER expression below which pCR was likely and to determine whether this cut-off value can identify patients who would benefit from adjuvant hormonal therapy.

Patients and methods

Patients with stage II or III HER2-negative primary breast cancer who received neoadjuvant chemotherapy followed by definitive surgery between June 1982 and June 2013 were included. Logistic regression models were used to assess the association between each variable and pCR. Cox models were used to analyze time to recurrence and overall survival. The recursive partitioning and regression trees method was used to calculate the cut-off value of ER expression.

Results

A total of 3055 patients were analyzed. Low percentage of ER was significantly associated with high pCR rate (OR = 0.99, 95% CI = 0.986-0.994, P < 0.001). The recommended cut-off of ER expression below which pCR was likely was 9.5%. Among patients with ER ≥ 10% tumors, but not those with 1%≤ER < 10% tumors, adjuvant hormonal therapy was significantly associated with long time to recurrence (HR = 0.24, 95% CI = 0.16-0.36, P < 0.001) and overall survival (HR = 0.32, 95% CI = 0.2-0.5, P < 0.001).

Conclusion

Stage II or III HER2-negative primary breast cancer with ER < 10% behaves clinically like triple-negative breast cancer in terms of pCR and survival outcomes and patients with such tumors may have a limited benefit from adjuvant hormonal therapy. It may be more clinically relevant to define triple-negative breast cancer as HER2-negative breast cancer with <10%, rather than <1%, of ER and/or progesterone receptor expression.

Abstract P4-14-02: CSF1/CSF1R axis reprograms epithelial-to-mesenchymal phenotypes in inflammatory breast cancer

Inflammatory breast cancer (IBC) accounts for 2% of breast cancers but 10% of breast cancer-related deaths in the US. Clinical hallmarks of IBC are tumor cell emboli in lymphatic vessels and overexpression of E-cadherin, which promotes cell clustering. Given these hallmarks, IBC is thought to spread via collective invasion and cell clusters. However, we showed that IBC cells underwent epithelial-to-mesenchymal transition (EMT) and metastasized through EMT. Thus, there are two contradictory theories of IBC metastasis. The objectives of this study were 1) to propose a model that reconciles these two models, and 2) to identify target molecules for inhibition of IBC metastasis. Methods: We previously showed that Matrigel culture induced EMT-like changes in SUM149 IBC cells. To test if this transformation from epithelial (E) to mesenchymal (M) in Matrigel culture is unique to IBC cells, a panel of breast cancer cells was cultured in both monolayer and Matrigel-coated plates. The cells were IBC (SUM149, SUM190, KPL4, IBC3), triple-negative breast cancer (TNBC) (MDA-MB-231, MDA-MB-468), and ER+ (MCF7) cells. Phenotypic changes in morphology and expression of EMT markers (E-cadherin, vimentin) were captured with bright field and immunofluorescent (IF) images, respectively. For genome-wide and targeted transcriptional analysis, SUM149 cells cultured in monolayer and Matrigel were processed using DNA microarrays and Taqman qRT-PCR. To correlate the Matrigel gene signature with M features in human breast cancer, a human breast cancer data set was hierarchically clustered with the Matrigel gene signature. Results: SUM149 cells showed a remarkable phenotypic change from E in monolayer culture to M in Matrigel. IF analysis confirmed induction of vimentin expression in Matrigel but stable expression of E-cadherin (thus, we refer to this state as E/M hybrid). This trend was also observed with SUM190 cells. Using qRT-PCR, we confirmed downregulation of E-cadherin and upregulation of M markers (vimentin, Twist1, Snail1, ZEB2) in Matrigel-cultured SUM149 and SUM190 cells compared to monolayer-cultured cells. DNA microarray transcriptional analysis confirmed this trend in SUM149 cells. TNBC has more M-like features than other breast cancer subtypes. Given this evidence, we clustered human breast cancer data using overexpressed genes in Matrigel-cultured SUM149 cells. We identified a cluster of 20 genes in TNBC samples and, assuming that these genes are drivers of E to E/M transition, chose the inflammation-related gene CSF1 as a candidate. The CSF1/CSF1R axis was inhibited by a CSF1R inhibitor, BLZ945; moreover, treatment with BLZ945 reversed the EMT changes in cells in Matrigel culture. Treatment with 5 μM BLZ945 re-induced E-cadherin expression and suppressed Snail1 and Twist1 expression in Matrigel-cultured SUM149 cells. Conclusion: IBC cells are more prone to undergo transition from E to E/M phenotype in Matrigel culture than are cells of other breast cancer subtypes. The CSF1/CSF1R axis plays a role in this E to E/M transition, thus warranting testing its significance using an in vivo IBC model. Phenotypic transition and reversion between E and E/M phenotypes could be a new paradigm that reconciles two contradictory models of IBC metastasis.

Citation Format: Kai K, Iwamoto T, Zhang D, Rao AUK, Thompson A, Sen S, Ueno NT. CSF1/CSF1R axis reprograms epithelial-to-mesenchymal phenotypes in inflammatory breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-14-02.

Endogenous Hydrogen Sulfide Contributes to Tone Generation in Porcine Lower Esophageal Sphincter Via Na+/Ca2+ Exchanger

BACKGROUND AND AIMS

Hydrogen sulfide (H₂S) is a major physiologic gastrotransmitter. Its role in the regulation of the lower esophageal sphincter (LES) function remains unknown. The present study addresses this question.

METHODS

Isometric contraction was monitored in circular smooth muscle strips of porcine LES. Changes in cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and force were simultaneously monitored in fura-2-loaded strips with front-surface fluorometry. The contribution of endogenous H₂S to LES contractility was investigated by examining the effects of inhibitors of H₂S-generating enzymes, including cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase, on the LES function.

RESULTS

Porcine LES strips myogenically maintained a tetrodotoxin-resistant basal tone. Application of AOA (cystathionine-β-synthase inhibitor) or L-aspartic acid (L-Asp; 3-mercaptopyruvate sulfurtransferase inhibitor) but not DL-PAG (cystathionine-γ-lyase inhibitor), decreased this basal tone. The relaxant effects of AOA and L-Asp were additive. Maximum relaxation was obtained by combination of 1 mM AOA and 3 mM L-Asp. Immunohistochemical analyses revealed that cystathionine-β-synthase and 3-mercaptopyruvate sulfurtransferase, but not cystathionine-γ-lyase, were expressed in porcine LES. AOA+L-Asp-induced relaxation was accompanied by a decrease in [Ca²⁺]_i and inversely correlated with the extracellular Na⁺ concentration ([Na⁺]_o) (25-137.4 mM), indicating involvement of an Na⁺/Ca²⁺ exchanger. The reduction in the basal [Ca²⁺]_i level by AOA was significantly augmented in the antral smooth muscle sheets of Na⁺/Ca²⁺ exchanger transgenic mice compared with wild-type mice.

CONCLUSIONS

Endogenous H₂S regulates the LES myogenic tone by maintaining the basal [Ca²⁺]_i via Na⁺/Ca²⁺ exchanger. H₂S-generating enzymes may be a potential therapeutic target for esophageal motility disorders, such as achalasia.

Shortest Double-Walled Carbon Nanotubes Composed of Cycloparaphenylenes

Invited for this month's cover is the group of Prof. Dr. Shigeru Yamago at the Kyoto University (Japan). The image shows the host-guest possibilities of cycloparaphenylenes (CPPs) of different sizes. Size selective interaction between [n]CPP and [n+5]CPP affords a host-guest complex, [n+5]CPP⊃[n]CPP, which is the shortest double-walled armchair carbon nanotube. The size-selective complex formation illustrates the importance of van der Waals interactions. A ternary complex, [15]CPP⊃[10]CPP⊃C₆₀ , also forms from [15]CPP, [10]CPP, and C₆₀ . Read the full text of the article at 10.1002/cplu.201700097.

Shortest Double-Walled Carbon Nanotubes Composed of Cycloparaphenylenes

The host-guest chemistry of cycloparaphenylenes (CPPs) of different sizes is described. [n]CPPs (n=5, 6, 7, 8, and 10) selectively interact with [n+5]CPPs, forming complexes [n+5]CPP⊃[n]CPP, which are the shortest double-walled armchair carbon nanotubes. The size selectivity is dictated by the difference in diameters of the CPPs (that is, 0.34-0.35 nm), which maximizes attractive van der Waals interactions. Theoretical calculations suggest that the orbital energies of the CPPs become perturbed upon complex formation, and orbital mixing between the two CPPs is predicted for large CPP pairs. The association constants in 1,1,2,2-[D₂ ]tetrachloroethane, estimated by ¹ H NMR titration, are approximately 10³  mol L^-1 at 50 °C. Van't Hoff plot analysis reveals that complexation is driven mainly by entropy owing to desolvation of the CPPs. [13]CPP also forms a complex with [4]cyclo-2,7-pyrenylene ([4]CPY), which is a π-extended [8]CPP. Theoretical calculations suggest that the formation of [13]CPP⊃[4]CPY is more exothermic than that of [13]CPP⊃[8]CPP. A ternary complex, [15]CPP⊃[10]CPP⊃C₆₀ , is also formed by mixing [15]CPP and [10]CPP⊃C₆₀ .

A subset of cerebrovascular pericytes originates from mature macrophages in the very early phase of vascular development in CNS

Pericytes are believed to originate from either mesenchymal or neural crest cells. It has recently been reported that pericytes play important roles in the central nervous system (CNS) by regulating blood-brain barrier homeostasis and blood flow at the capillary level. However, the origin of CNS microvascular pericytes and the mechanism of their recruitment remain unknown. Here, we show a new source of cerebrovascular pericytes during neurogenesis. In the CNS of embryonic day 10.5 mouse embryos, CD31⁺F4/80⁺ hematopoietic lineage cells were observed in the avascular region around the dorsal midline of the developing midbrain. These cells expressed additional macrophage markers such as CD206 and CD11b. Moreover, the CD31⁺F4/80⁺ cells phagocytosed apoptotic cells as functionally matured macrophages, adhered to the newly formed subventricular vascular plexus, and then divided into daughter cells. Eventually, these CD31⁺F4/80⁺ cells transdifferentiated into NG2/PDGFRβ/desmin-expressing cerebrovascular pericytes, enwrapping and associating with vascular endothelial cells. These data indicate that a subset of cerebrovascular pericytes derive from mature macrophages in the very early phase of CNS vascular development, which in turn are recruited from sites of embryonic hematopoiesis such as the yolk sac by way of blood flow.