Functional studies of acetylcholine, ATP and cytokine release from the human carotid body: the new frontier for oxygen chemoreception physiology

Universal CRISPR/Cas12a-associated aptasensor suitable for rapid detection of small proteins with a plate reader

With the discovery of the collateral cleavage activity, CRISPR/Cas12a has recently been identified as a key enabling approach in novel DNA biosensor development. Despite its remarkable success in nucleic acid detection, realizing a universal CRISPR/Cas biosensing system for non-nucleic acid targets remains challenging, particularly at extremely high sensitivity ranges for analyte concentrations lower than the pM level. DNA aptamers can be designed to bind to a range of specific target molecules, such as proteins, small molecules, and cells, with high affinity and specificity through configuration changes. Here, by harnessing its diverse analyte-binding ability and also redirecting the specific DNA-cutting activity of Cas12a to selected aptamers, a simple, sensitive, and universal biosensing platform has been established, termed CRISPR/Cas and aptamer-mediated extra-sensitive assay (CAMERA). With simple modifications to the aptamer and guiding RNA of Cas12a RNP, CAMERA demonstrated 100 fM sensitivity for targeting small proteins, such as IFN-γ and insulin, with less than 1.5-h detection time. Compared with the gold-standard ELISA, CAMERA achieved higher sensitivity and a shorter detection time while retaining ELISA's simple setup. By replacing the antibody with an aptamer, CAMERA also achieved improved thermal stability, allowing to eliminate the requirement for cold storage. CAMERA shows potential to be used as a replacement for conventional ELISA for a variety of diagnostics but with no significant changes for the experimental setup.

Functional glutamate transporters are expressed in the carotid chemoreceptor

BACKGROUND

The carotid body (CB) plays a critical role in cyclic intermittent hypoxia (CIH)-induced chemosensitivity; however, the underlying mechanism remains uncertain. We have demonstrated the presence of multiple inotropic glutamate receptors (iGluRs) in CB, and that CIH exposure alters the level of some iGluRs in CB. This result implicates glutamatergic signaling in the CB response to hypoxia. The glutamatergic neurotransmission is not only dependent on glutamate and glutamate receptors, but is also dependent on glutamate transporters, including vesicular glutamate transporters (VGluTs) and excitatory amino acid transporters (EAATs). Here, we have further assessed the expression and distribution of VGluTs and EAATs in human and rat CB and the effect of CIH exposure on glutamate transporters expression.

METHODS

The mRNA of VGluTs and EAATs in the human CB were detected by RT-PCR. The protein expression of VGluTs and EAATs in the human and rat CB were detected by Western blot. The distribution of VGluT3, EAAT2 and EAAT3 were observed by immunohistochemistry staining and immunofluorescence staining. Male Sprague-Dawley (SD) rats were exposed to CIH (FIO₂ 10-21%, 3 min/3 min for 8 h per day) for 2 weeks. The unpaired Student's t-test was performed.

RESULTS

Here, we report on the presence of mRNAs for VGluT1-3 and EAAT1-3 in human CB, which is consistent with our previous results in rat CB. The proteins of VGluT1 and 3, EAAT2 and 3, but not VGluT2 and EAAT1, were detected with diverse levels in human and rat CB. Immunostaining showed that VGluT3, the major type of VGluTs in CB, was co-localized with tyrosine hydroxylase (TH) in type I cells. EAAT2 and EAAT3 were distributed not only in type I cells, but also in glial fibrillary acidic protein (GFAP) positive type II cells. Moreover, we found that exposure of SD rats to CIH enhanced the protein level of EAAT3 as well as TH, but attenuated the levels of VGluT3 and EAAT2 in CB.

CONCLUSIONS

Our study suggests that glutamate transporters are expressed in the CB, and that glutamate transporters may contribute to glutamatergic signaling-dependent carotid chemoreflex to CIH.