5 research outputs found
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Monitoring response to a clinically relevant IDH inhibitor in gliomaâHyperpolarized 13C magnetic resonance spectroscopy approaches
BackgroundMutant isocitrate dehydrogenase (IDHmut) catalyzes 2-hydroxyglutarate (2HG) production and is considered a therapeutic target for IDHmut tumors. However, response is mostly associated with inhibition of tumor growth. Response assessment via anatomic imaging is therefore challenging. Our goal was to directly detect IDHmut inhibition using a new hyperpolarized (HP) 13C magnetic resonance spectroscopy-based approach to noninvasively assess α-ketoglutarate (αKG) metabolism to 2HG and glutamate.MethodsWe studied IDHmut-expressing normal human astrocyte (NHAIDH1mut) cells and rats with BT257 tumors, and assessed response to the IDHmut inhibitor BAY-1436032 (nâ
â„â
4). We developed a new 13C Echo Planar Spectroscopic Imaging sequence with an optimized RF pulse to monitor the fate of HP [1-13C]αKG and [5-12C,1-13C]αKG with a 2.5â
Ăâ
2.5â
Ăâ
8 mm3 spatial resolution.ResultsCell studies confirmed that BAY-1436032-treatment leads to a drop in HP 2HG and an increase in HP glutamate detectable with both HP substrates. Data using HP [5-12C,1-13C]αKG also demonstrated that its conversion to 2HG is detectable without the proximal 1.1% natural abundance [5-13C]αKG signal. In vivo studies showed that glutamate is produced in normal brains but no 2HG is detectable. In tumor-bearing rats, we detected the production of both 2HG and glutamate, and BAY-1436032-treatment led to a drop in 2HG and an increase in glutamate. Using HP [5-12C,1-13C]αKG we detected metabolism with an signal-to-noise ratio of 23 for 2HG and 17 for glutamate.ConclusionsOur findings point to the clinical potential of HP αKG, which recently received FDA investigational new drug approval for research, for noninvasive localized imaging of IDHmut status
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Structural Relationships to Efficacy for Prazole-Derived Antivirals.
Here, an in vitro characterization of a family of prazole derivatives that covalently bind to the C73 site on Tsg101 and assay their ability to inhibit viral particle production is presented. Structurally, increased steric bulk on the 4-pyridyl of the prazole expands the prazole site on the UEV domain toward the ÎČ-hairpin in the Ub-binding site and is coupled to increased inhibition of virus-like particle production in HIV-1. Increased bulk also increased toxicity, which is alleviated by increasing flexibility. Further, the formation of a novel secondary Tsg101 adduct for several of the tested compounds and the commercial drug lansoprazole. The secondary adduct involved the loss of the 4-pyridyl substituent to form an irreversible species, with implications for increasing the half-life of the active species or its specificity toward Tsg101 UEV. It is also determined that sulfide derivatives display effective viral inhibition, presumably through cellular sulfoxidation, allowing for delayed conversion within the cellular environment, and identify SARS-COV-2 as a target of prazole inhibition. These results open multiple avenues for the design of prazole derivatives for antiviral applications
Rapid <sup>13</sup>C Hyperpolarization of the TCA Cycle Intermediate 뱉Ketoglutarate via SABRE-SHEATH
α-Ketoglutarate is a key biomolecule involved in
a number
of metabolic pathwaysmost notably the TCA cycle. Abnormal
α-ketoglutarate metabolism has also been linked with cancer.
Here, isotopic labeling was employed to synthesize [1-13C,5-12C,D4]α-ketoglutarate with the future
goal of utilizing its [1-13C]-hyperpolarized state for
real-time metabolic imaging of α-ketoglutarate analytes and
its downstream metabolites in vivo. The signal amplification
by reversible exchange in shield enables alignment transfer to heteronuclei
(SABRE-SHEATH) hyperpolarization technique was used to create 9.7%
[1-13C] polarization in 1 minute in this isotopologue.
The efficient 13C hyperpolarization, which utilizes parahydrogen
as the source of nuclear spin order, is also supported by favorable
relaxation dynamics at 0.4 ÎŒT field (the optimal polarization
transfer field): the exponential 13C polarization buildup
constant Tb is 11.0 ± 0.4 s whereas
the 13C polarization decay constant T1 is 18.5 ± 0.7 s. An even higher 13C polarization
value of 17.3% was achieved using natural-abundance α-ketoglutarate
disodium salt, with overall similar relaxation dynamics at 0.4 ÎŒT
field, indicating that substrate deuteration leads only to a slight
increase (âŒ1.2-fold) in the relaxation rates for 13C nuclei separated by three chemical bonds. Instead, the gain in
polarization (natural abundance versus [1-13C]-labeled)
is rationalized through the smaller heat capacity of the âspin
bathâ comprising available 13C spins that must be
hyperpolarized by the same number of parahydrogen present in each
sample, in line with previous 15N SABRE-SHEATH studies.
Remarkably, the C-2 carbon was not hyperpolarized in both α-ketoglutarate
isotopologues studied; this observation is in sharp contrast with
previously reported SABRE-SHEATH pyruvate studies, indicating that
the catalyst-binding dynamics of C-2 in α-ketoglutarate differ
from that in pyruvate. We also demonstrate that 13C spectroscopic
characterization of α-ketoglutarate and pyruvate analytes can
be performed at natural 13C abundance with an estimated
detection limit of 80 micromolar concentration Ă *%P13C. All in all, the fundamental studies reported here
enable a wide range of research communities with a new hyperpolarized
contrast agent potentially useful for metabolic imaging of brain function,
cancer, and other metabolically challenging diseases