Near-Infrared II Photobiomodulation Preconditioning Ameliorates Stroke Injury via Phosphorylation of eNOS.

BACKGROUND: The current management of patients with stroke with intravenous thrombolysis and endovascular thrombectomy is effective only when it is timely performed on an appropriately selected but minor fraction of patients. The development of novel adjunctive therapy is highly desired to reduce morbidity and mortality with stroke. Since endothelial dysfunction is implicated in the pathogenesis of stroke and is featured with suppressed endothelial nitric oxide synthase (eNOS) with concomitant nitric oxide deficiency, restoring endothelial nitric oxide represents a promising approach to treating stroke injury. METHODS: This is a preclinical proof-of-concept study to determine the therapeutic effect of transcranial treatment with a low-power near-infrared laser in a mouse model of ischemic stroke. The laser treatment was performed before the middle cerebral artery occlusion with a filament. To determine the involvement of eNOS phosphorylation, unphosphorylatable eNOS S1176A knock-in mice were used. Each measurement was analyzed by a 2-way ANOVA to assess the effect of the treatment on cerebral blood flow with laser Doppler flowmetry, eNOS phosphorylation by immunoblot analysis, and stroke outcomes by infarct volumes and neurological deficits. RESULTS: Pretreatment with a 1064-nm laser at an irradiance of 50 mW/cm2 improved cerebral blood flow, eNOS phosphorylation, and stroke outcomes. CONCLUSIONS: Near-infrared II photobiomodulation could offer a noninvasive and low-risk adjunctive therapy for stroke injury. This new modality using a physical parameter merits further consideration to develop innovative therapies to prevent and treat a wide array of cardiovascular diseases.

Near-infrared II photobiomodulation augments nitric oxide bioavailability via phosphorylation of endothelial nitric oxide synthase.

There is solid evidence of the beneficial effect of photobiomodulation (PBM) with low-power near-infrared (NIR) light in the NIR-I window in increasing bioavailable nitric oxide (NO). However, it is not established whether this effect can be extended to NIR-II light, limiting broader applications of this therapeutic modality. Since we have demonstrated PBM with NIR laser in the NIR-II window, we determined the causal relationship between NIR-II irradiation and its specific biological effects on NO bioavailability. We analyzed the impact of NIR-II irradiation on NO release in cultured human endothelial cells using a NO-sensitive fluorescence probe and single-cell live imaging. Two distinct wavelengths of NIR-II laser (1064 and 1270 nm) and NIR-I (808 nm) at an irradiance of 10 mW/cm2 induced NO release from endothelial cells. These lasers also enhanced Akt phosphorylation at Ser 473, endothelial nitric oxide synthase (eNOS) phosphorylation at Ser 1177, and endothelial cell migration. Moreover, the NO release and phosphorylation of eNOS were abolished by inhibiting mitochondrial respiration, suggesting that Akt activation caused by NIR-II laser exposure involves mitochondrial retrograde signaling. Other inhibitors that inhibit known Akt activation pathways, including a specific inhibitor of PI3K, Src family PKC, did not affect this response. These two wavelengths of NIR-II laser induced no appreciable NO generation in cultured neuronal cells expressing neuronal NOS (nNOS). In short, NIR-II laser enhances bioavailable NO in endothelial cells. Since a hallmark of endothelial dysfunction is suppressed eNOS with concomitant NO deficiency, NIR-II laser technology could be broadly used to restore endothelial NO and treat or prevent cardiovascular diseases.

Photobiomodulation and nitric oxide signaling.

Nitric oxide (NO) is a well-known gaseous mediator that maintains vascular homeostasis. Extensive evidence supports that a hallmark of endothelial dysfunction, which leads to cardiovascular diseases, is endothelial NO deficiency. Thus, restoring endothelial NO represents a promising approach to treating cardiovascular complications. Despite many therapeutic agents having been shown to augment NO bioavailability under various pathological conditions, success in resulting clinical trials has remained elusive. There is solid evidence of diverse beneficial effects of the treatment with low-power near-infrared (NIR) light, defined as photobiomodulation (PBM). Although the precise mechanisms of action of PBM are still elusive, recent studies consistently report that PBM improves endothelial dysfunction via increasing bioavailable NO in a dose-dependent manner and open a feasible path to the use of PBM for treating cardiovascular diseases via augmenting NO bioavailability. In particular, the use of NIR light in the NIR-II window (1000-1700 nm) for PBM, which has reduced scattering and minimal tissue absorption with the largest penetration depth, is emerging as a promising therapy. In this review, we update recent findings on PBM and NO.

In vivo quantification of programmed death-ligand-1 expression heterogeneity in tumors using fluorescence lifetime imaging.

Cancer patient selection for immunotherapy is often based on programmed death-ligand-1 (PD-L1) expression as a biomarker. PD-L1 expression is currently quantified using immunohistochemistry, which can only provide snapshots of PD-L1 expression status in microscopic regions of ex vivo specimens. In vivo imaging using targeted agents can capture dynamic variations of PD-L1 expression in entire tumors within and across multiple subjects. Towards this goal, several PD-L1 targeted molecular imaging probes have been evaluated in murine models and humans. However, clinical translation of these probes has been limited due to a significant non-specific accumulation of the imaging probes and the inability of conventional imaging modalities to provide quantitative readouts that can be compared across multiple subjects. Here we report that in vivo time-domain (TD) fluorescence imaging can provide quantitative estimates of baseline tumor PD-L1 heterogeneity across untreated mice and variations in PD-L1 expression across mice undergoing clinically relevant anti-PD1 treatment. This approach relies on a significantly longer fluorescence lifetime (FLT) of PD-L1 specific anti-PD-L1 antibody tagged to IRDye 800CW (αPDL1-800) compared to nonspecific αPDL1-800. Leveraging this unique FLT contrast, we show that PD-L1 expression can be quantified across mice both in superficial breast tumors using planar FLT imaging, and in deep-seated liver tumors (>5 mm depth) using the asymptotic TD algorithm for fluorescence tomography. Our results suggest that FLT contrast can accelerate the preclinical investigation and clinical translation of novel molecular imaging probes by providing robust quantitative readouts of receptor expression that can be readily compared across subjects.

Preventing NK cell activation in the damaged liver induced by cabozantinib/PD-1 blockade increases survival in hepatocellular carcinoma models.

The addition of anti-VEGF antibody treatment to immune checkpoint blockade (ICB) has increased the efficacy of immunotherapy in advanced hepatocellular carcinoma (HCC). Despite an initial promise, adding multitargeted kinase inhibitors of VEGFR with ICB has failed to increase survival in HCC. To reveal the mechanisms underlying treatment failure, we studied the effects of cabozantinib/ICB using orthotopic murine HCC models with or without liver damage. We monitored tumor growth and liver function, recorded survival outcomes, and performed immune profiling studies for intra-tumoral and surrounding liver. Cabozantinib/ICB treatment led to tumor regression and significantly improved survival in mice with normal livers. However, consistent with the clinical findings, combination therapy failed to show survival benefits despite similar tumor control when tested in the same models but in mice with liver fibrosis. Moreover, preclinical and clinical data converged, showing that activating immune responses by cabozantinib/ICB treatment induced hepatoxicity. Immune profiling revealed that combination therapy effectively reprogrammed the tumor immune microenvironment and increased NK cell infiltration and activation in the damaged liver tissue. Surprisingly, systemic depletion of NK reduced hepatotoxicity elicited by the combination therapy without compromising its anti-cancer effect, and significantly enhanced the survival benefit even in mice with HCC and underlying liver fibrosis. These findings demonstrate that preventing NK activation allowed for maintaining a favorable therapeutic ratio when combining ICB with cabozantinib in advanced HCC models.