Acute neuropathy mimicking porphyria induced by aminolevulinic acid during photodynamic therapy

Intraoperative Tumor Detection Using Pafolacianine

Cancer is a leading cause of death worldwide, with increasing numbers of new cases each year. For the vast majority of cancer patients, surgery is the most effective procedure for the complete removal of the malignant tissue. However, relapse due to the incomplete resection of the tumor occurs very often, as the surgeon must rely primarily on visual and tactile feedback. Intraoperative near-infrared imaging with pafolacianine is a newly developed technology designed for cancer detection during surgery, which has been proven to show excellent results in terms of safety and efficacy. Therefore, pafolacianine was approved by the U.S. Food and Drug Administration (FDA) on 29 November 2021, as an additional approach that can be used to identify malignant lesions and to ensure the total resection of the tumors in ovarian cancer patients. Currently, various studies have demonstrated the positive effects of pafolacianine’s use in a wide variety of other malignancies, with promising results expected in further research. This review focuses on the applications of the FDA-approved pafolacianine for the accurate intraoperative detection of malignant tissues. The cancer-targeting fluorescent ligands can shift the paradigm of surgical oncology by enabling the visualization of cancer lesions that are difficult to detect by inspection or palpation. The enhanced detection and removal of hard-to-detect cancer tissues during surgery will lead to remarkable outcomes for cancer patients and society, specifically by decreasing the cancer relapse rate, increasing the life expectancy and quality of life, and decreasing future rates of hospitalization, interventions, and costs.

Mechanisms of Neuronal Damage in Acute Hepatic Porphyrias

Porphyrias are a group of congenital and acquired diseases caused by an enzymatic impairment in the biosynthesis of heme. Depending on the specific enzyme involved, different types of porphyrias (i.e., chronic vs. acute, cutaneous vs. neurovisceral, hepatic vs. erythropoietic) are described, with different clinical presentations. Acute hepatic porphyrias (AHPs) are characterized by life-threatening acute neuro-visceral crises (acute porphyric attacks, APAs), featuring a wide range of neuropathic (central, peripheral, autonomic) manifestations. APAs are usually unleashed by external "porphyrinogenic" triggers, which are thought to cause an increased metabolic demand for heme. During APAs, the heme precursors δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) accumulate in the bloodstream and urine. Even though several hypotheses have been developed to explain the protean clinical picture of APAs, the exact mechanism of neuronal damage in AHPs is still a matter of debate. In recent decades, a role has been proposed for oxidative damage caused by ALA, mitochondrial and synaptic ALA toxicity, dysfunction induced by relative heme deficiency on cytochromes and other hemeproteins (i.e., nitric oxide synthases), pyridoxal phosphate functional deficiency, derangements in the metabolic pathways of tryptophan, and other factors. Since the pathway leading to the biosynthesis of heme is inscribed into a complex network of interactions, which also includes some fundamental processes of basal metabolism, a disruption in any of the steps of this pathway is likely to have multiple pathogenic effects. Here, we aim to provide a comprehensive review of the current evidence regarding the mechanisms of neuronal damage in AHPs.

Endoscopic therapies for Barrett's esophagus

The management of Barrett's esophagus (BE) has evolved as newer technologies and novel methods are developed. Endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) are the initial interventions of choice for nodular BE, with ESD reserved for endoscopists highly trained in the technique and for larger lesions that would warrant en bloc resection. Resection should then be followed by ablative therapy, which remains first line in the treatment of BE with dysplasia. Although there is a myriad of ablation techniques available to the endoscopist, this review has found that radiofrequency ablation (RFA) continues to have the most robust safety and efficacy data to support its use despite a relatively high rate of recurrence. Cryotherapy and Hybrid-APC appear to be safe and effective as RFA alternatives, but further trials are still needed to directly compare their outcomes to RFA and ultimately guide changes in treatment decisions.

The acute hepatic porphyrias

The acute hepatic porphyrias (AHP) are a group of four inherited diseases of heme biosynthesis. They present with similar severe, episodic, acute neurovisceral symptoms due to abnormally elevated levels of porphyrin precursors delta-aminolevulinic acid (ALA). Recently genetic screening indicates that the prevalence of mutation carrier state is more common than previously thought, occurring in 1 in 1,500, though the clinical penetrance of symptomatic AHP is low at ~1%. Symptomatic attacks occur primarily in females during their reproductive years. In an acute porphyria attack, the primary symptom is abdominal pain, due to intestinal dysmotility from autonomic nerve injury. Other manifestations include seizures, weakness and mood changes, point to injury involving peripheral and central nervous system. Due to the non-specific nature of the symptoms and signs in AHP, the diagnosis is often delayed by many years. The diagnosis of AHP depends on biochemical evidence of elevated ALA and PBG levels in urine during symptomatic attacks. Genetic testing is used for confirmation of the gene involved and the exact mutation. Treatment involves administration of heme, which downregulates production of ALA. Long-term management centers on educating genetic carriers on avoiding triggers that increase the risk of acute attacks and screening family members.

Tailoring photosensitive ROS for advanced photodynamic therapy

Photodynamic therapy (PDT) has been considered a noninvasive and cost-effective modality for tumor treatment. However, the complexity of tumor microenvironments poses challenges to the implementation of traditional PDT. Here, we review recent advances in PDT to resolve the current problems. Major breakthroughs in PDTs are enabling significant progress in molecular medicine and are interconnected with innovative strategies based on smart bio/nanomaterials or therapeutic insights. We focus on newly developed PDT strategies designed by tailoring photosensitive reactive oxygen species generation, which include the use of proteinaceous photosensitizers, self-illumination, or oxygen-independent approaches. While these updated PDT platforms are expected to enable major advances in cancer treatment, addressing future challenges related to biosafety and target specificity is discussed throughout as a necessary goal to expand the usefulness of PDT.

Self-luminescent photodynamic therapy using breast cancer targeted proteins

Despite the potential of photodynamic therapy (PDT), its comprehensive use in cancer treatment has not been achieved because of the nondegradable risks of photosensitizing drugs and limits of light penetration and instrumentation. Here, we present bioluminescence (BL)-induced proteinaceous PDT (BLiP-PDT), through the combination of luciferase and a reactive oxygen species (ROS)-generating protein (Luc-RGP), which is self-luminescent and degradable. After exposure to coelenterazine-h as a substrate for luciferase without external light irradiation, Luc-RGP fused with a small lead peptide-induced breast cancer cell death through the generation of BL-sensitive ROS in the plasma membrane. Even with extremely low light energy, BLiP-PDT exhibited targeted effects in primary breast cancer cells from patients and in in vivo tumor xenograft mouse models. These findings suggest that BLiP-PDT is immediately useful as a promising theranostic approach against various cancers.

Preanesthetic severe postural hypotension following 5-aminolevulinic acid pretreatment in patients for photodynamic diagnosis-assisted urological surgery

BACKGROUND

5-Aminolevulinic acid (5-ALA) is utilized for photodynamic diagnosis-assisted (PDD) surgery. However, it has been associated with vasodilation, hence, occasional hypotension.

CASE PRESENTATION

We encountered two patients who had severe postural hypotension following 5-ALA pretreatment prior to an operation. They were scheduled for urological PDD surgery, but upon standing to walk to the operation room, they felt sick because of severe hypotension. One of them underwent the surgery after recovery, but the other surgery was canceled due to a prolonged hypotension that lasted for more than a day.

CONCLUSIONS

Severe postural hypotension may develop as a result of the high concentration of porphyrin precursors, which may affect the nervous system. Severe postural hypotension may be due to 5-ALA-induced autonomic dysfunction as well as vasodilative action of 5-ALA. These observations suggest that in addition to the careful monitoring of patients' vital signs, standing should be avoided following 5-ALA pretreatment.

Dichloroacetate-induced peripheral neuropathy

Dichloroacetate (DCA) has been the focus of research by both environmental toxicologists and biomedical scientists for over 50 years. As a product of water chlorination and a metabolite of certain industrial chemicals, DCA is ubiquitous in our biosphere at low μg/kg body weight daily exposure levels without obvious adverse effects in humans. As an investigational drug for numerous congenital and acquired diseases, DCA is administered orally or parenterally, usually at doses of 10-50mg/kg per day. As a therapeutic, its principal mechanism of action is to inhibit pyruvate dehydrogenase kinase (PDK). In turn, PDK inhibits the key mitochondrial energy homeostat, pyruvate dehydrogenase complex (PDC), by reversible phosphorylation. By blocking PDK, DCA activates PDC and, consequently, the mitochondrial respiratory chain and ATP synthesis. A reversible sensory/motor peripheral neuropathy is the clinically limiting adverse effect of chronic DCA exposure and experimental data implicate the Schwann cell as a toxicological target. It has been postulated that stimulation of PDC and respiratory chain activity by DCA in normally glycolytic Schwann cells causes uncompensated oxidative stress from increased reactive oxygen species production. Additionally, the metabolism of DCA interferes with the catabolism of the amino acids phenylalanine and tyrosine and with heme synthesis, resulting in accumulation of reactive molecules capable of forming adducts with DNA and proteins and also resulting in oxidative stress. Preliminary evidence in rodent models of peripheral neuropathy suggest that DCA-induced neurotoxicity may be mitigated by naturally occurring antioxidants and by a specific class of muscarinic receptor antagonists. These findings generate a number of testable hypotheses regarding the etiology and treatment of DCA peripheral neuropathy.

Photodynamic Therapy for Barrett's Esophagus and Esophageal Carcinoma

This paper reviews the use of photodynamic therapy (PDT) in patients with Barrett's esophagus and esophageal carcinoma. We describe the history of PDT, mechanics, photosensitizers for PDT in patients with esophageal disease. Finally, we discuss its utility and limitations in this setting.

The role of photodynamic therapy in the esophagus

Photodynamic therapy (PDT) is a drug and device therapy using photosensitizer drugs activated by laser light for mucosal ablation. Porfimer sodium PDT has been used extensively with proven long-term efficacy and durability for the ablation of Barrett esophagus and high-grade dysplasia. and early esophageal adenocarcinoma. However, continued use is hampered by an associated stricture risk and prolonged photosensitivity (4-6 weeks). Promising single-center European studies using other forms of PDT, such as aminolevulinic acid PDT, have not been replicated elsewhere, limiting the widespread use of other forms of PDT. Future use of PDT in esophageal disease depends on the development of improved dosimetry and patient selection to optimize treatment outcomes, while minimizing adverse events and complications.

Photodynamic therapy using 5-aminolaevulinic acid for the treatment of dysplasia in Barrett's oesophagus

BACKGROUND

5-Aminolaevulinic acid (ALA) is the naturally occurring metabolic precursor of an endogenously formed photosensitiser, protoporphyrin IX. It is used topically to treat benign and malignant skin disorders by a process called photodynamic therapy (PDT). Recently, data are emerging on its systemic use in the treatment of dysplasia in Barrett's oesophagus.

OBJECTIVE

To investigate the use of ALA-PDT for the treatment of dysplasia and early cancer in Barrett's oesophagus.

METHODS

A systematic literature review and synopsis is given.

CONCLUSION

ALA is an attractive alternative to the currently approved photosensitiser (porfimer sodium) due to its oral route of administration, shorter generalised skin photosensitivity period and lower rate of stricture formation. The studies presented demonstrate that ALA-PDT is both safe and effective for the treatment of dysplasia and early cancer in Barrett's oesophagus.

Technology insight: Photodynamic therapy for cholangiocarcinoma

Cholangiocarcinoma is, in most cases, rapidly fatal. Curative resection can only be offered to approximately 10% of patients. Even after seemingly curative resection, recurrence frequently occurs. Adjuvant chemotherapy and/or radiotherapy do not reduce the recurrence rate after resection. In the palliative setting, endoscopic or percutaneous biliary drainage is performed to relieve jaundice; however, poor results have been obtained in patients with tumors involving the intrahepatic bile ducts. Biliary drainage alleviates jaundice, but there is no evidence that it prolongs life. Palliative chemotherapy and/or radiotherapy have not been proven to prolong life and relieve jaundice. Photodynamic therapy (PDT) is a relatively new local, minimally invasive procedure that can be used to treat cholangiocarcinoma. PDT uses the physical properties of light-absorbing molecules, so-called photosensitizers, which accumulate within proliferating cells. Activation of the photosensitizer by a non-thermal laser leads to selective photochemical destruction of tumors. In a randomized trial of patients with nonresectable cholangiocarcinoma, PDT prolonged survival time, improved cholestasis and quality of life considerably, and had a favorable side-effect profile. A second randomized trial confirmed the beneficial effect of PDT. For the time being, PDT is recommended for patients with nonresectable disease. The role of PDT before and after surgical resection needs to be assessed.