Innate Sensors Trigger Regulated Cell Death to Combat Intracellular Infection.

Intracellular pathogens pose a significant threat to animals. In defense, innate immune sensors attempt to detect these pathogens using pattern recognition receptors that either directly detect microbial molecules or indirectly detect their pathogenic activity. These sensors trigger different forms of regulated cell death, including pyroptosis, apoptosis, and necroptosis, which eliminate the infected host cell niche while simultaneously promoting beneficial immune responses. These defenses force intracellular pathogens to evolve strategies to minimize or completely evade the sensors. In this review, we discuss recent advances in our understanding of the cytosolic pattern recognition receptors that drive cell death, including NLRP1, NLRP3, NLRP6, NLRP9, NLRC4, AIM2, IFI16, and ZBP1.

Caspase-7 activates ASM to repair gasdermin and perforin pores.

Among the caspases that cause regulated cell death, a unique function for caspase-7 has remained elusive. Caspase-3 performs apoptosis, whereas caspase-7 is typically considered an inefficient back-up. Caspase-1 activates gasdermin D pores to lyse the cell; however, caspase-1 also activates caspase-7 for unknown reasons1. Caspases can also trigger cell-type-specific death responses; for example, caspase-1 causes the extrusion of intestinal epithelial cell (IECs) in response to infection with Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium)2,3. Here we show in both organoids and mice that caspase-7-deficient IECs do not complete extrusion. Mechanistically, caspase-7 counteracts gasdermin D pores and preserves cell integrity by cleaving and activating acid sphingomyelinase (ASM), which thereby generates copious amounts of ceramide to enable enhanced membrane repair. This provides time to complete the process of IEC extrusion. In parallel, we also show that caspase-7 and ASM cleavage are required to clear Chromobacterium violaceum and Listeria monocytogenes after perforin-pore-mediated attack by natural killer cells or cytotoxic T lymphocytes, which normally causes apoptosis in infected hepatocytes. Therefore, caspase-7 is not a conventional executioner but instead is a death facilitator that delays pore-driven lysis so that more-specialized processes, such as extrusion or apoptosis, can be completed before cell death. Cells must put their affairs in order before they die.

Small intestinal stem cell identity is maintained with functional Paneth cells in heterotopically grafted epithelium onto the colon.

To develop stem cell therapy for small intestinal (SI) diseases, it is essential to determine whether SI stem cells in culture retain their tissue regeneration capabilities. By using a heterotopic transplantation approach, we show that cultured murine SI epithelial organoids are able to reconstitute self-renewing epithelia in the colon. When stably integrated, the SI-derived grafts show many features unique only to the SI but distinct from the colonic epithelium. Our study provides evidence that cultured adult SI stem cells could be a source for cell therapy of intestinal diseases, maintaining their identity along the gastrointestinal tract through an epithelium-intrinsic mechanism.

Wideband slow short-pulse propagation in one-thousand slantingly coupled L3 photonic crystal nanocavities.

Coupled cavities have been used previously to realize on-chip low-dispersion slow-light waveguides, but the bandwidth was usually narrower than 10 nm and the total length was much shorter than 1 mm. Here we report long (0.05-2.5 mm) slow-light coupled cavity waveguides formed by using 50, 200, and 1,000 L3 photonic crystal nanocavities with an optical volume smaller than (λ/n)3, slanted from Γ-K orientation. We demonstrate experimentally the formation of a single-mode wideband coupled cavity mode with a bandwidth of up to 32nm (4THz) in telecom C-band, generated from the ultra-narrow-band (~300 MHz) fundamental mode of each L3 nanocavity, by controlling the cavity array orientation. Thanks to the ultrahigh-Q nanocavity design, coupled cavity waveguides longer than 1 mm exhibited low loss and allowed time-of-flight dispersion measurement over a bandwidth up to 22 nm by propagating a short pulse over 1,000 coupled L3 nanocavities. The highly-dense slanted array of L3 nanocavity demonstrated unprecedentedly high cavity coupling among the nanocavities. The scheme we describe provides controllable planar dispersion-managed waveguides as an alternative to W1-based waveguides on a photonic crystal chip.

Room temperature continuous-wave nanolaser diode utilized by ultrahigh-Q few-cell photonic crystal nanocavities.

Few-cell point-defect photonic crystal (PhC) nanocavities (such as LX and H1 type cavities), have several unique characteristics including an ultra-small mode volume (Vm), a small device footprint advantageous for dense integration, and a large mode spacing advantageous for high spontaneous-emission coupling coefficient (ß), which are promising for energy-efficient densely-integratable on-chip laser light sources enhanced by the cavity QED effect. To achieve this goal, a high quality factor (Q) is essential, but conventional few-cell point-defect cavities do not have a sufficiently high Q. Here we adopt a series of modified designs of LX cavities with a buried heterostructure (BH) multi-quantum-well (MQW) active region that can achieve a high Q while maintaining their original advantages and fabricate current-injection laser devices. We have successfully observed continuous-wave (CW) lasing in InP-based L1, L2, L3 and L5 PhC nanocavities at 23°C with a DC current injection lower than 10 µA and a bias voltage lower than 0.9 V. The active volume is ultra-small while maintaining a sufficiently high confinement factor, which is as low as ~10-15 cm3 for a single-cell (L1) nanocavity. This is the first room-temperature current-injection CW lasing from any types of few-cell point-defect PhC nanocavities (LX or H1 types). Our report marks an important step towards realizing a nanolaser diode with a high cavity-QED effect, which is promising for use with on-chip densely integrated laser sources in photonic networks-on-chip combined with CMOS processors.

All-optical switching for 10-Gb/s packet data by using an ultralow-power optical bistability of photonic-crystal nanocavities.

An all-optical packet switching using bistable photonic crystal nanocavity memories was demonstrated for the first time. Nanocavity-waveguide coupling systems were configured for 1 × 1, 1 × 2, and 1 × 3 switches for 10-Gb/s optical packet, and they were all operated with an optical bias power of only a few µW. The power is several magnitudes lower than that of previously reported all-optical packet switches incorporating all-optical memories. A theoretical investigation indicated the optimum design for reducing the power consumption even further, and for realizing a higher data-rate capability and higher extinction. A small footprint and integrability are also features of our switches, which make them attractive for constructing an all-optical packet switching subsystem with a view to realizing optical routing on a chip.

25-channel all-optical gate switches realized by integrating silicon photonic crystal nanocavities.

Silicon-based photonic crystal nanocavities with different lattice pitches were monolithically integrated with a total length of only 200 µm, and were operated as a multi-channel all-optical switch with a large processing density of 42 Tb/s/mm2. A pump light and a signal light were assigned to two cavity modes in each cavity, and in this way all-optical gate switching was achieved in a 25 channel resonant dip with an energy cost in the femtojoule regime. We also demonstrated a wavelength-division multiplexing operation by selecting three neighboring channels, and thus achieved gate switching without inter-channel optical crosstalk. As far as we know, this was the first demonstration of a many-channel all-optical switch that can handle an optical signal with bit-by-bit Gb/s repetition in an integrated photonic crystal chip.

Compact 1D-silicon photonic crystal electro-optic modulator operating with ultra-low switching voltage and energy.

We demonstrate a small foot print (600 nm wide) 1D silicon photonic crystal electro-optic modulator operating with only a 50 mV swing voltage and 0.1 fJ/bit switching energy at GHz speeds, which are the lowest values ever reported for a silicon electro-optic modulator. A 3 dB extinction ratio is demonstrated with an ultra-low 50 mV swing voltage with a total device energy consumption of 42.8 fJ/bit, which is dominated by the state holding energy. The total energy consumption is reduced to 14.65 fJ/bit for a 300 mV swing voltage while still keeping the switching energy at less than 2 fJ/bit. Under optimum voltage conditions, the device operates with a maximum speed of 3 Gbps with 8 dB extinction ratio, which rises to 11 dB for a 1 Gbps modulation speed.

Systematic hole-shifting of L-type nanocavity with an ultrahigh Q factor.

We report simple systematic hole-shifting rules applicable to any Lx (x:2,3,4,5,…) nanocavity. The rules specify six sets of holes to be tuned with only two or three shift parameters. While keeping the same cavity wavelength and nearly the same mode volume, the new rule increases the Q factor by nearly one order of magnitude compared with an edge-hole-shifted Lx nanocavity. The Q factor of the high-order mode is also greatly increased. This merit is obvious from the maximum experimental Q factors of over 500,000 at L2 and of over 1,000,000 at L3, L4, and L5 achieved in Si photonic crystals.

NLRP3, NLRP6, and NLRP12 are inflammasomes with distinct expression patterns.

Inflammasomes are sensors that detect cytosolic microbial molecules or cellular damage, and in response they initiate a form of lytic regulated cell death called pyroptosis. Inflammasomes signal via homotypic protein-protein interactions where CARD or PYD domains are crucial for recruiting downstream partners. Here, we screened these domains from NLR family proteins, and found that the PYD domain of NLRP6 and NLRP12 could activate caspase-1 to induce cleavage of IL-1ß and GSDMD. Inflammasome reconstitution verified that full length NLRP6 and NLRP12 formed inflammasomes in vitro, and NLRP6 was more prone to auto-activation. NLRP6 was highly expressed in intestinal epithelial cells (IEC), but not in immune cells. Molecular phylogeny analysis found that NLRP12 was closely related to NLRP3, but the activation mechanisms are different. NLRP3 was highly expressed in monocytes and macrophages, and was modestly but appreciably expressed in neutrophils. In contrast, NLRP12 was specifically expressed in neutrophils and eosinophils, but was not detectable in macrophages. NLRP12 mutations cause a periodic fever syndrome called NLRP12 autoinflammatory disease. We found that several of these patient mutations caused spontaneous activation of caspase-1 in vitro, which likely causes their autoinflammatory disease. Different cell types have unique cellular physiology and structures which could be perturbed by a pathogen, necessitating expression of distinct inflammasome sensors to monitor for signs of infection.

InGaAs nano-photodetectors based on photonic crystal waveguide including ultracompact buried heterostructure.

Ultrasmall InGaAs photodetectors based on a photonic crystal waveguide with a buried heterostructure (BH) were demonstrated for the first time. A sufficiently high DC responsivity of ~1 A/W was achieved for the 3.4-µm-long detector. The dynamic response revealed a 3-dB bandwidth of 6 GHz and a 10-Gb/s eye pattern. These results were thanks to the strong confinement of both photons and carriers in a small BH and will pave the way for unprecedented nano-photodetectors with a high quantum efficiency and small capacitance. Our device potentially has an ultrasmall junction capacitance of much less than 1 fF and may enable us to eliminate electrical amplifiers for future optical receivers and subsequent ultralow-power optical links on a chip.

Ultralow-energy and high-contrast all-optical switch involving Fano resonance based on coupled photonic crystal nanocavities.

We experimentally and theoretically clarified that a Fano resonant system based on a coupled optical cavity has better performance when used as an all-optical switch than a single cavity in terms of switching energy, contrast, and operation bandwidth. We successfully fabricated a Fano system consisting of doubly coupled photonic-crystal (PhC) nanocavities, and demonstrated all-optical switching for the first time. A steep asymmetric transmission spectrum was clearly observed, thereby enabling a low-energy and high-contrast switching operation. We achieved the switching with a pump energy of a few fJ, a contrast of more than 10 dB, and an 18 ps switching time window. These levels of performance are actually better than those for Lorentzian resonance in a single cavity. We also theoretically investigated the achievable performance in a well-designed Fano system, which suggested a high contrast for the switching of more than 20 dB in a fJ energy regime.

Bucket lists must be completed during cell death.

Regulated cell death occurs in many forms, including apoptosis, pyroptosis, necroptosis, and NETosis. Most obviously, the purpose of these pathways is to kill the cell. However, many cells need to complete a set of effector programs before they die, which we define as a cellular 'bucket list'. These effector programs are specific to the cell type, and mode and circumstances of death. For example, intestinal epithelial cells need to complete the process of extrusion before they die. Cells use regulatory mechanisms to temporarily prolong their life, including endosomal sorting complex required for transport (ESCRT)- and acid sphingomyelinase (ASM)-driven membrane repair. These allow cells to complete their bucket lists before they die.

Real-time analysis of P-glycoprotein-mediated drug transport across primary intestinal epithelium three-dimensionally cultured in vitro.

P-glycoprotein (P-gp) is an efflux transporter that regulates bioavailability of orally administered drugs at the intestinal epithelium. To develop an in vitro experimental model that mimics P-gp-mediated intestinal drug transport in vivo, we employed normal intestinal epithelium three-dimensionally cultured. Physiological expression of P-gp mRNA and the expression of its protein at the apical membrane were observed in the small intestinal epithelium grown as cystic organoids. Rhodamine123 (Rh123), a substrate for P-gp, was actively transported in the basoapical direction and accumulated in the luminal space, while the epithelial integrity was kept intact. Furthermore, we were able to monitor the whole process of Rh123 transport and its inhibition by verapamil in real-time, from which kinetic parameters for Rh123 transport could be estimated by a mathematical modeling. The method here described to evaluate the dynamics of P-gp-mediated transport in primary intestinal epithelial cells would be instrumental in investigating the physiological function of P-gp and its inhibitors/inducers in vitro.

Narrow linewidth operation of buried-heterostructure photonic crystal nanolaser.

We investigate the spectral linewidth of a monolithic photonic crystal nanocavity laser. The nanocavity laser is based on a buried heterostructure cavity in which an ultra-small InGaAsP active region is embedded in an InP photonic crystal. Although it was difficult to achieve narrow linewidth operation in previously reported photonic crystal nanocavity lasers, we have successfully demonstrated a linewidth of 143.5 MHz, which is far narrower than the cold cavity linewidth and the narrowest value yet reported for nanolasers and photonic crystal lasers. The narrow linewidth is accompanied by a low power consumption and an ultrasmall footprint, thus making this particular laser especially suitable for use as an integrated multi-purpose sensor.

Room-temperature continuous-wave operation of lateral current injection wavelength-scale embedded active-region photonic-crystal laser.

We have developed a wavelength-scale embedded active-region photonic-crystal laser using lateral p-i-n structure. Zn diffusion and Si ion implantation are used for p- and n-type doping. Room-temperature continuous-wave lasing behavior is clearly observed from the injection current dependence of the output power, 3dB-bandwidth of the peak, and lasing wavelength. The threshold current is 390 µA and the estimated effective threshold current is 9.4 µA. The output power in output waveguide is 1.82 µW for a 2.0-mA current injection. These results indicate that the embedded active-region structure effectively reduce the thermal resistance. Ultrasmall electrically driven lasers are an important step towards on-chip photonic network applications.

Radiation vs surgery for early-stage laryngeal verrucous carcinoma: A population-based propensity score matched-study.

BACKGROUND: Verrucous carcinoma (VC) is a rare variant of squamous cell carcinoma. Although VC is considered radioresistant, concrete evidence for this is absent. METHODS: We obtained data on VC treated with surgery or radiation from the Surveillance, Epidemiology, and End Results database. Treatment selection bias was reduced by propensity score matching. Overall survival (OS) and disease-specific survival (DSS) rates were estimated using the Kaplan-Meier method. Hazard ratios (HRs) were estimated using Cox proportional hazards models. RESULTS: Five-year OS rates in the radiation and surgery groups were 72.7% and 72.0%, respectively (P = 0.111); five-year DSS rates in the same were 86.7% and 88.4%, respectively (P = 0.234). HRs of radiation compared with surgery were 1.68 (95% confidence interval (CI), 0.96-2.95) for OS and 1.95 (95% CI, 0.69-5.53) for DSS. CONCLUSIONS: Similar prognoses were observed in patients with VC treated with radiation and surgery. VC can be treated using radiation.

The AIM2 inflammasome is activated in astrocytes during the late phase of EAE.

Inflammasomes are a class of innate immune signaling platforms that activate in response to an array of cellular damage and pathogens. Inflammasomes promote inflammation under many circumstances to enhance immunity against pathogens and inflammatory responses through their effector cytokines, IL-1ß and IL-18. Multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), are autoimmune conditions influenced by inflammasomes. Despite work investigating inflammasomes during EAE, little remains known concerning the role of inflammasomes in the central nervous system (CNS) during the disease. Here, we used multiple genetically modified mouse models to monitor activated inflammasomes in situ based on oligomerization of apoptosis-associated speck-like protein containing a CARD (ASC) in the spinal cord. Using inflammasome reporter mice, we found heightened inflammasome activation in astrocytes after the disease peak. In contrast, microglia and CNS-infiltrated myeloid cells had few activated inflammasomes in the CNS during EAE. Astrocyte inflammasome activation during EAE was dependent on absent in melanoma 2 (AIM2), but low IL-1ß release and no significant signs of cell death were found. Thus, the AIM2 inflammasome activation in astrocytes may have a distinct role from traditional inflammasome-mediated inflammation.

40-Gb/s directly-modulated photonic crystal lasers under optical injection-locking.

CMOS integrated circuits (IC) usually requires high data bandwidth for off-chip input/output (I/O) data transport with sufficiently low power consumption in order to overcome pin-count limitation. In order to meet future requirements of photonic network interconnect, we propose an optical output device based on an optical injection-locked photonic crystal (PhC) laser to realize low-power and high-speed off-chip interconnects. This device enables ultralow-power operation and is suitable for highly integrated photonic circuits because of its strong light-matter interaction in the PhC nanocavity and ultra-compact size. High-speed operation is achieved by using the optical injection-locking (OIL) technique, which has been shown as an effective means to enhance modulation bandwidth beyond the relaxation resonance frequency limit. In this paper, we report experimental results of the OIL-PhC laser under various injection conditions and also demonstrate 40-Gb/s large-signal direct modulation with an ultralow energy consumption of 6.6 fJ/bit.